Showing papers in "International Journal of Epidemiology in 2001"

Theories for social epidemiology in the 21st century: an ecosocial perspective

Abstract: In social epidemiology, to speak of theory is simultaneously to speak of society and biology. It is, I will argue, to speak of embodiment. At issue is how we literally incorporate, biologically, the world around us, a world in which we simultaneously are but one biological species among many—and one whose labour and ideas literally have transformed the face of this earth. To conceptualize and elucidate the myriad social and biological processes resulting in embodiment and its manifestation in populations' epidemiological profiles, we need theory. This is because theory helps us structure our ideas, so as to explain causal connections between specified phenomena within and across specified domains by using interrelated sets of ideas whose plausibility can be tested by human action and thought.1–3 Grappling with notions of causation, in turn, raises not only complex philosophical issues but also, in the case of social epidemiology, issues of accountability and agency: simply invoking abstract notions of ‘society’ and disembodied ‘genes’ will not suffice. Instead, the central question becomes: who and what is responsible for population patterns of health, disease, and well-being, as manifested in present, past and changing social inequalities in health?

On the importance—and the unimportance— of birthweight

Abstract: Birthweight is one of the most accessible and most misunderstood variables in epidemiology. A baby's weight at birth is strongly associated with mortality risk during the first year and, to a lesser degree, with developmental problems in childhood and the risk of various diseases in adulthood. Epidemiological analyses often regard birthweight as on the causal pathway to these health outcomes. Under this assumption of causality, birthweight is used to explain variations in infant mortality and later morbidity, and is also used as an intermediate health endpoint in itself. Evidence presented here suggests the link between birthweight and health outcomes may not be causal. Methods of analysis that assume causality are unreliable at best, and biased at worst. The category of 'low birthweight' in particular is uninformative and seldom justified. The main utility of the birthweight distribution is to provide an estimate of the proportion of small preterm births in a population (although even this requires special analytical methods). While the ordinary approaches to birthweight are not well grounded, the links between birthweight and a range of health outcomes may nonetheless reflect the workings of biological mechanisms with implications for human health.

Cross-national comparison of childhood obesity: the epidemic and the relationship between obesity and socioeconomic status

Abstract: Background Obesity has become a worldwide epidemic. Recently WHO acknowledged an urgent need to examine child obesity across countries using a standardized international standard. Studies in adults find obesity and socioeconomic factors (SES) factors are correlated, but results are inconsistent for children. Using an international standard, we examined the prevalence of obesity and compared the associations between SES factors and obesity across countries. Methods Data for children aged 6‐18 from nationwide surveys in the US (NHANES III, 1988‐1994), China (1993), and Russia (1992) were used. We used the recently updated US NCHS body mass index (BMI = wt/ht 2 ) reference to define obesity (BMI >95th percentile) and overweight (85th

The nutritional basis of the fetal origins of adult disease

Abstract: It is now widely accepted that the risks of a number of chronic diseases in adulthood may have their origins before birth. Such diseases include non insulin-dependent diabetes mellitus, hypertension and coronary heart disease. Professor David Barker and colleagues in Southampton have produced a large proportion of the data in this field over the last decade, 1 although the relationship between early life events and adult disease had been raised many years earlier. 2 Most of this work has been based on epidemiological studies wherein cohorts of subjects whose birth records were available have been traced into adulthood. They have shown that measurements made on babies at birth, including birthweight, length, body proportions and placental weight, are strongly related to either later disease incidence (coronary heart disease mortality, noninsulin-dependent diabetes) 3,4 or risk factors for those diseases (hypertension, glucose intolerance, hyperlipidaemia). 1,5,6 Such relationships have been shown to hold in many different populations and are apparent from early childhood. 7,8 The basis of these epidemiological observations is proposed to be that of programming. That is, an event operating at a critical or sensitive period results in a long-term change in the structure or function of the organism. Programming is a well-established biological phenomenon, and there are many common and well-known examples. Female rats given testosterone during the first 4 days of life develop a male pattern of gonatotropin secretion after puberty, and despite normal ovarian and pituitary function, fail to develop normal patterns of female sexual behaviour. 9 Administration of androgen at 10 days of age has

Self-rated health. Comparisons between three different measures. Results from a population study

Abstract: Background Self-rating of health is among the most frequently assessed health perceptions in epidemiological research. The aim of this study was to compare different measures of global self-rated health (SRH) with respect to differences in age and sex groups and relations to hypothesized determinants. Method Three single-question measures of SRH were included in a health questionnaire administered to 8200 randomly chosen men and women. Two SRH measures were non-comparative, one with seven (SRH-7) and one with five response options (SRH-5), while the third measure included a comparison with others of the same age (SRH-age). SRH-7 had specified response options only at the ends of the scale, while the other two measures gave specified statements for each option. Comparisons between the SRH assessments were studied with respect to response frequencies, frequency distributions, age and gender differences and differences in associations with hypothesized determinants. Results The differences between the SRH measures were in most cases marginal. Some diversities may, however, be worth considering: a high drop-out rate for the SRH-7 measure in the oldest age group; a trend that SRH-7 correlated most strongly with the independent variables; SRH-age showed improved health ratings with increasing age but a less skewed frequency distribution compared to the non-comparative measures. Conclusions The results imply that non-comparative measures are more appropriate in longitudinal studies and that measures without specified response options might be less suitable for an older study group. The overall impression is, however, that the different measures represents parallel assessments of subjective health.

Validation of self-reported hearing loss. The Blue Mountains Hearing Study

Abstract: Purpose Large-scale epidemiological studies have often used self-report to estimate prevalence of age-related hearing loss. However, few large population-based studies have validated self-report against measured hearing loss. Our study aimed to assess the performance of a single question and a brief hearing handicap questionnaire in identifying individuals with hearing loss, against the gold standard of pure-tone audiometry. Methods We examined 2015 residents, aged 55-99 years, living in the west of Sydney, Australia, who participated in the Blue Mountains Hearing Study during 1997-1999. Audiologists administered a comprehensive questionnaire, including the question: 'Do you feel you have a hearing loss?' The Shortened Hearing Handicap Inventory for Elderly (HHIE-S) was also administered during the hearing examination, which included pure-tone audiometry. The single question and HHIE-S were compared with measured losses at levels >25, >40 and >60 decibels hearing level (dBHL) to indicate mild, moderate and marked hearing impairment, for pure-tone averages (PTA) of responses to 500, 1000, 2000 and 4000 Hz. Results The single question yielded reasonable sensitivity and specificity for hearing impairment, and was minimally affected by age and gender. HHIE-S scores >8 had lower sensitivity but higher specificity and positive predictive value. The HHIE-S performed slightly better in younger than older subjects and performed better for moderate hearing impairment. Conclusions In this older population with a high prevalence of hearing loss (39.4%), both a question about hearing and the HHIE-S appeared sufficiently sensitive and specific to provide reasonable estimates of hearing loss prevalence. Both could be recommended for use in epidemiological studies that aim to assess the magnitude of the burden caused by age-related sensory impairment but cannot measure hearing loss by audiometry.

Epidemiological assessment of diet: a comparison of a 7-day diary with a food frequency questionnaire using urinary markers of nitrogen, potassium and sodium

Abstract: Background Validation studies of dietary instruments developed for epidemiological studies have typically used some form of diet record as the standard for comparison. Recent work suggests that comparison with diet record may overestimate the ability of the epidemiological instrument to measure habitual dietary intake, due to lack of independence of the measurement errors. The degree of regression dilution in estimating diet-disease association may therefore have been correspondingly underestimated. Use of biochemical measures of intake may mitigate the problem. In this paper, we report on the use of urinary measures of intakes of nitrogen, potassium and sodium to compare the performance of a semi-quantitative food frequency questionnaire (FFQ) and a 7-day diet diary (7DD) to estimate average intake of these nutrients over one year. Methods In all, 179 individuals were asked to complete an FFQ and a 7DD on two occasions separated by approximately 12 months. The individuals were also asked to provide 24-hour urine samples on six occasions over a 6-9-month period, covering the time at which the record FFQ and 7DD were completed. The urine was assayed for nitrogen, potassium and sodium. The protocol was completed by 123 individuals. The data from these individuals were analysed to estimate the covariance structure of the measurement errors of the FFQ, the 7DD and a single 24-hour urine measurement, and to estimate the degree of regression dilution associated with the FFQ and 7DD. Results The results demonstrated that: (1) the error variances for each of the three nutrients was more than twice as great with the FFQ than the 7DD; (2) there was substantial correlation (0.46-0.58) between the error of both the FFQ and the 7DD completed on different occasions; (3) there was moderate correlation (0.24- 0.29) between the error in the FFQ and the error in the 7DD for each nutrient; (4) the correlation between errors in different nutrients was higher for the FFQ (0.77-0.80) than for the 7DD (0.52-0.70). Conclusions The regression dilution with the FFQ is considerably greater than with the 7DD and also, for the nutrients considered, greater than would be inferred if validation studies were based solely on record or diary type instruments.

Cigarette smoking and diabetes mellitus: evidence of a positive association from a large prospective cohort study.

Abstract: Objective Only a few prospective studies have examined the relationship between the frequency of cigarette smoking and the incidence of diabetes mellitus. The purpose of this study was to determine whether greater frequency of cigarette smoking accelerated the development of diabetes mellitus, and whether quitting reversed the effect. Methods Data were collected in the Cancer Prevention Study I, a prospective cohort study conducted from 1959 through 1972 by the American Cancer Society where volunteers recruited more than one million acquaintances in 25 US states. From these over one million original participants, 275 190 men and 434 637 women aged >30 years were selected for the primary analysis using predetermined criteria. Results As smoking increased, the rate of diabetes increased for both men and women. Among those who smoked >2 packs per day at baseline, men had a 45% higher diabetes rate than men who had never smoked; the comparable increase for women was 74%. Quitting smoking reduced the rate of diabetes to that of nonsmokers after 5 years in women and after 10 years in men. Conclusions A dose-response relationship seems likely between smoking and incidence of diabetes. Smokers who quit may derive substantial benefit from doing so. Confirmation of these observations is needed through additional epidemiological and biological research.

Diet and socioeconomic position: does the use of different indicators matter?

Abstract: Objectives To describe the association of diet and socioeconomic position and to assess whether two different indicators, education and occupation, independently contribute in determining diet. Methods A community-based random sample of men and women residents of Geneva canton, aged 35 to 74, participated in a survey of cardiovascular risk factors conducted annually since 1993. Lifetime occupational and educational history and a semi-quantitative food frequency questionnaire were obtained from 2929 men and 2767 women. Results Subjects from lower education and/or occupation consumed less fish and vegetables but more fried foods, pasta and potatoes, table sugar and beer. Iron, calcium, vitamin A and vitamin D intake were lower in the lower educational and occupational groups. Both indicators significantly contributed to determining a less healthy dietary pattern for those from low social class. The effects of education and occupation on dietary habits were usually additive and synergistic for some food groups. Conclusion Assessing both education and occupation, improves the description of social class inequalities in dietary habits, as they act, most of the time, as independent factors.

Support from children, living arrangements, self-rated health and depressive symptoms of older people in Spain

Abstract: Objective To assess the association between emotional and instrumental support from Objective To assess the association between emotional and instrumental support from children and living arrangements with the physical and mental health of older people in Spain. Methods A face-to-face home interview was carried out with 1284 community-dwelling people over 65 (response rate = 83%) randomly sampled according to an age-and sex-stratified sampling scheme in 1993 at Leganes (Spain). Close to 93% of the participants had children and 45% of them coresided with them. Depressive symptoms were assessed by the CES-D (Center for Epidemiologic study depression scale) and self-rated health (SRH) by a single-item question. Emotional support was measured with a six-item scale on affection and reciprocity. Instrumental support was assessed by help received from children in 17 activities of daily living. Four living arrangements were considered: Living with spouse only, living with a spouse and children, widower living alone, and widower living with children. Results Multivariate analysis controlling for age, gender, education and functional status showed that low emotional support and reception of instrumental aid were significantly associated with poor SRH. Being a widower and sharing living arrangements with children was associated with good SRH. Living arrangements modify some of the associations of support of children with SRH. Depressive symptoms were associated with low emotional support, reception of instrumental help and being a widower who did not share living arrangements with children. For widowers who do not cohabit with children, reception of instrumental aid is associated with low depressive symptomatology. Discussion Emotional support from children seems to play an important role in maintaining the physical and mental health of elderly people in Spain. Instrumental support is widely available. Coresidence with children is very common and it is associated with good self-perceived health and low prevalence of depressive symptoms in a culture where family interdependence is highly valued. Families should be protected and encouraged to continue care-giving through a variety of community services and respite care, adapted to their needs and preferences. Research should be undertaken to find more efficient ways to help family caregivers in the Mediterranean context.

Childhood socioeconomic position and cognitive function in adulthood

Abstract: *This article is free to read on the publisher's website* Background Risk of dementia and Alzheimer's disease is higher among adults with limited education, and the less educated perform poorer on cognitive function tests. This study determines whether the socioeconomic environment experienced during childhood has an impact on cognitive functioning in middle age. Methods A population-based study of eastern Finnish men (n = 496) aged 58 and 64 for whom there were data on parent's socioeconomic position (SEP), their own education level, and performance on neuropsychological tests. Cognitive function was measured using the Trail Making Test, the Selective Reminding Test, the Verbal Fluency Test, the Visual Reproduction Test, and the Mini Mental State Exam. Results We found a significant and graded association between parental SEP (combined as an index) and cognitive function both prior to and after adjustment for respondent's education. Those from more disadvantaged backgrounds exhibited the poorest performance. When the separate components of the parental SEP measure were used, father's occupation and mother's education were independently associated with the respondent's score for three and five of the tests, respectively (there was no association with father's education and mother's occupation). After adjustment for the respondent's education, father's occupation was no longer associated with respondent's test score, however, the results were essentially unchanged for mother's education. Conclusions Higher SEP during childhood and greater educational attainment are both associated with cognitive function in adulthood, with mothers and fathers each contributing to their offspring's formative cognitive development and later life cognitive ability (albeit in different ways). Improvements in both parental socioeconomic circumstances and the educational attainment of their offspring could possibly enhance cognitive function and decrease risk of dementia later in life.

Ecologic versus individual-level sources of bias in ecologic estimates of contextual health effects

Abstract: A number of authors have attempted to defend ecologic (aggregate) studies by claiming that the goal of those studies is estimation of ecologic (contextual or group-level) effects rather than individual-level effects. Critics of these attempts point out that ecologic effect estimates are inevitably used as estimates of individual effects, despite disclaimers. A more subtle problem is that ecologic variation in the distribution of individual effects can bias ecologic estimates of contextual effects. The conditions leading to this bias are plausible and perhaps even common in studies of ecosocial factors and health outcomes because social context is not randomized across typical analysis units (administrative regions). By definition, ecologic data contain only marginal observations on the joint distribution of individually defined confounders and outcomes, and so identify neither contextual nor individual-level effects. While ecologic studies can still be useful given appropriate caveats, their problems are better addressed by multilevel study designs, which obtain and use individual as well as group-level data. Nonetheless, such studies often share certain special problems with ecologic studies, including problems due to inappropriate aggregation and problems due to temporal changes in covariate distributions.

Self-rated health and limiting longstanding illness: inter-relationships with morbidity in early adulthood.

Abstract: BACKGROUND: Self-rated health and limiting longstanding illness are both widely used global measures of health, but understanding is poor of their meaning and validity at younger ages. METHODS: We examined the association between self-rated health and limiting longstanding illness and specific health problems at two ages (23 and 33 years), and assessed change over the 10-year period for each health measure relative to another. Longitudinal data were taken from the nationally representative British birth cohort for which health measures were obtained at ages 23 and 33. RESULTS: Self-rated health and limiting longstanding illness were strongly associated with each other as well as with specific health problems, particularly with serious conditions (e.g. epilepsy, cancer, diabetes) and more weakly with less serious conditions (e.g. eczema and hay fever). Rating of overall health and limiting longstanding illness was highly stable during the 10-year period with most, but not all, health change reflecting a deterioration in health status. Deterioration in limiting illness corresponded to an even greater health decline in specific conditions. CONCLUSIONS: Self-rated health and limiting longstanding illness are valid health measures appropriate for use in general health surveys.

Intake of vegetables rich in carotenoids and risk of coronary heart disease in men: The Physicians' Health Study

Abstract: Background Previous studies of diet and coronary heart disease (CHD) have focused on intake of nutrients rather than whole foods. Because of the findings that dietary fibre, folate and antioxidants may be protective for CHD, increased intake of vegetables has been recommended. However, due to the chemical and physical complexity of vegetables, the effects of individual nutrients may differ if eaten as whole foods. Moreover, little is known about the direct association between vegetable intake and risk of CHD. Methods We prospectively evaluated the relation between vegetable intake and CHD risk in the Physicians’ Health Study, a randomized trial of aspirin and beta-carotene among 22 071 US male physicians aged 40‐84 years in 1982. In this analysis, we included 15 220 men without heart disease, stroke or cancer at baseline who provided information on their vegetable intake at baseline, and in the 2nd, 4th and 6th years of follow-up using a simple semiquantitative food frequency questionnaire including eight vegetables. We confirmed 1148 incident cases of CHD (387 incident cases of myocardial infarction and 761 incident cases of coronary artery bypass grafting or percutaneous transluminal coronary angioplasty) during 12 years of follow-up. Results After adjusting for age, randomized treatment, body mass index (BMI), smoking, alcohol intake, physical activity, history of diabetes, history of hypertension, history of high cholesterol, and use of multivitamins, men who consumed at least 2.5 servings/day of vegetables had a relative risk (RR) of 0.77 (95% CI : 0.60‐0.98) for CHD, compared with men in the lowest category (,1 serving/day). Adjusting for the same covariates in an analysis of the overall trend that considered intake of vegetables as a continuous variable, we found a RR of 0.83 (95% CI : 0.71‐0.98) for risk of CHD for each additional serving/day of vegetables. The inverse relation between vegetable intake and CHD risk was more evident among men with a BMI >25 (RR = 0.71, 95% CI : 0.51‐0.99) or current smokers (RR = 0.40, 95% CI : 0.18‐0.86) comparing highest to the lowest categories of intake. Conclusions Our results suggest an inverse association between vegetable intake and risk of CHD. These prospective data support current dietary guidelines to increase vegetable intake for the prevention of CHD.

A national record linkage to study acute myocardial infarction incidence and case fatality in Sweden.

Abstract: During the last decades substantial temporal changes, as well as population differences, in coronary heart disease mortality have occurred in Sweden. There is little information to what extent these changes and differences also apply to myocardial infarction incidence, The aim of this paper was to describe the methods used to identify cases in a recently developed National Acute Myocardial Infarction Register in Sweden, and to present estimates of incidence and case fatality in Sweden. I Incident cases of acute myocardial infarction (AMI) were identified by record linkage of routinely collected data on hospital discharges and deaths. Case fatality within 28 days was ascertained by linkage of incident cases to the National Cause of Death Register. About 40 000 new cases of AMI per year were recorded in Sweden during 1987-1995. Well-known differences in incidence with regard to age and gender were observed, as well as a decline in incidence between 1987 and 1995. A similar case fatality was seen in men and women aged 30-89 among hospitalized cases. When fatal cases outside hospital were also considered the case fatality was somewhat higher in men. Examination of medical records for a national sample of ischaemic heart disease patients suggested a high sensitivity (94%) and a high positive predictive value (86%) for ICD-9 code 410 in hospital discharge data with regard to definite AMI. The National Acute Myocardial Infarction Register offers a new possibility to study the incidence of AMI, as well as case fatality, in Sweden.

Socioeconomic inequalities in all-cause and specific-cause mortality in Australia: 1985–1987 and 1995–1997

Abstract: Background. Socioeconomic inequalities in mortality have been repeatedly observed in Britain, the United States, and Europe, and in some countries, there is evidence that the differentials are widening. This study describes trends in socioeconomic mortality inequality in Australia for males and females aged 0-14, 15-24 and 25-64 years over the period 1985-87 to 1995-97. Methods. SES was operationalised using the Index of Relative Socioeconomic Disadvantage, an area based measure developed by the Australian Bureau of Statistics. Mortality differentials were examined using age-standardised rates, and mortality inequality was assessed using rate ratios, gini coefficients, and a measure of excess mortality. Results. For both periods, and for each sex/age sub-group, mortality rates were highest in the most disadvantaged areas. The extent and nature of socioeconomic mortality inequality differed for males and females and for each age group: both increases and decreases in mortality inequality were observed, and for some causes, the degree of inequality remained unchanged. If it were possible to reduce death rates among the SES areas to a level equivalent to that of the least disadvantaged area, premature all–cause mortality for males in the three age groups would be lower by 22%, 28% and 26% respectively, and for females, 35%, 70% and 56%. Conclusions. The mortality burden in the Australian population attributable to socioeconomic inequality is large, and has profound and far-reaching implications in terms of the unnecessary loss of life, the loss of potentially economically productive members of society, and increased costs for the health care system. Keywords: Socioeconomic status, mortality inequality, Australia, area-based measures.

Risk factors for Alzheimer's disease: a population-based, longitudinal study in Manitoba, Canada

Abstract: Background Current knowledge of risk factors for Alzheimer’s disease (AD) is limited. Data from a longitudinal, population-based study of dementia in Manitoba, Canada were used to investigate risk factors for AD. Methods Cognitively intact subjects completed a risk factor questionnaire assessing sociodemographic, genetic, environmental, medical and lifestyle exposures. Five years later, 36 subjects had developed AD and 658 remained cognitively intact. Results Older subjects or those who had fewer years of education were at greater risk of AD. After adjusting for age, education and sex, occupational exposure to fumigants/ defoliants was a significant risk factor for AD (relative risk [RR] = 4.35; 95% CI : 1.05‐17.90). A history of migraines increased the risk of AD (RR = 3.49; 95% CI : 1.39‐8.77); an even stronger effect was noted among women. Self-reported memory loss at baseline was associated with subsequent development of AD (RR = 5.15; 95% CI : 2.36‐11.27). Vaccinations and occupational exposure to excessive noise reduced the risk of AD. Conclusions Some well-known risk factors for AD were confirmed in this study and potential new risk factors were identified. The association of AD with a history of migraines and occupational exposure to defoliants/fumigants is of particular interest because these are biologically plausible risk factors.

Oesophageal and gastric cardia adenocarcinomas: analysis of regional variation using the Cancer Incidence in Five Continents database

Abstract: Background Adenocarcinomas of the oesophagus and proximal stomach are the most rapidly increasing malignancies in some countries; however, there are no comparative studies on global disease incidence, and the relationships between these two malignancies are undefined. Methods We evaluated the cumulative rates and age-specific incidence rates per 100 000 population for adenocarcinomas of the oesophagus and proximal stomach for all countries in the Cancer Incidence in Five Continents database, and compared them with rates for oesophageal squamous cell carcinoma. Results Substantial variations in cumulative cancer rates were found between genders, between countries, between different ethnicities within the same country, and within the same ethnicity residing in different countries. Cumulative rates (ages 0-74 years) for oesophageal adenocarcinoma varied from 0 (e.g. Thailand) to 0.6 (Scotland, males, 95% CI : 0.56, 0.64); for proximal stomach cancer from 0 (Singapore, Malay females, 95% CI : -0.01, 0.11) to 0.52 (The Netherlands, males, 95% CI : 0.49, 0.55); and for oesophageal squamous cell carcinomas from 0 (non-Jews in Israel, females) to 1.84 (Brazil, Porto Alegre, males, 95% CI : 1.42, 2.26). There was a continuous increase in age-specific incidence rates with advancing age for oesophageal/proximal stomach adenocarcinomas, but a decrease in age-specific incidence rates for oesophageal squamous cell carcinoma after age 75 years. The cumulative rate trends for adenocarcinomas of the oesophagus and proximal stomach were often dissimilar, and varied by country, gender, and ethnicity. Conclusions These results suggest that different risk factors may be associated with adenocarcinomas of the oesophagus versus the proximal stomach; the marked rate variation implies a substantial environmental component to the recent incidence changes.

Fetal experience and good adult design

Abstract: Biology is the study of complicated things that give the appearance of having been designed for a purpose. This thought has been articulated most clearly in recent years by Richard Dawkins, 1 but it has been expressed in various ways for 200 years. A traveller finding a watch on a mountain path would not fail to attribute the quality of its design to human agency. A great British naturalist and theologian, William Paley 2 regarded the design he saw everywhere in nature as proof of the existence of God. These days, the design to which Paley referred would instead be attributed by most biologists to blind Darwinian evolution. The form and behaviour of individuals vary within the same species and, in any given set of environmental conditions, some individuals may be better able to survive and reproduce than others because their distinctive characteristics are particularly well suited to those conditions. If their characteristics are inherited, then an ever increasing number of individuals in the population will be better adapted to that environment than was previously the case. Plant and animal breeders have known for years how to select artificially the characteristics which they prized for one reason or another. Darwin called the blind evolutionary process leading to the appearance of good design ‘natural selection’. 3 His phrase was popular in the 19th century because it suggested an agent for evolution. These days many biologists prefer to focus on the processes. What generates variation in the first place? What leads to differential survival and reproductive success? What genetic and environmental factors enable individual characteristics to be replicated in subsequent generations? While each of these questions raises separate issues, it is worth keeping in mind the idea of the evolutionary outcome—apparent design.

A history of physical activity, cardiovascular health and longevity: the scientific contributions of Jeremy N Morris, DSc, DPH, FRCP

Abstract: Since Hippocrates first advised us more than 2000 years ago that exercise-though not too much of it--was good for health, the epidemiology of physical activity has developed apace with the epidemiological method itself. It was only in the mid-20th century that Professor Jeremy N Morris and his associates used quantitative analyses, which dealt with possible selection and confounding biases, to show that vigorous exercise protects against coronary heart disease (CHD). They began by demonstrating an apparent protection against CHD enjoyed by active conductors compared with sedentary drivers of London double-decker buses. In addition, postmen seemed to be protected against CHD like conductors, as opposed to less active government workers. The Morris group pursued the matter further, adapting classical infectious disease epidemiology to the new problems of chronic, non-communicable diseases. Realizing that if physical exercise were to be shown to contribute to the prevention of CHD, it would have to be accomplished through study of leisure-time activities, presumably because of a lack of variability in intensities of physical work. Accordingly, they chose typical sedentary middle-management grade men for study, obtained 5-minute logs of their activities over a 2-day period, and followed them for non-fatal and fatal diseases. In a subsequent study, Morris et al. queried such executive-grade civil servants by detailed mail-back questionnaires on their health habits and health status. They then followed these men for chronic disease occurrence, as in the earlier survey. By 1973 they had distinguished between 'moderately vigorous' and 'vigorous' exercise. In both of these civil service surveys, they demonstrated strong associations between moderately vigorous or vigorous exercise and CHD occurrence, independent of other associations, in age classes 35-64 years. In the last 30 years, with modern-day computers, a large number of epidemiological studies have been conducted in both sexes, in different ethnic groups, in broad age classes, in a variety of social groups, and on most continents of the world. These studies have extended and amplified those of the Morris group, thereby helping to solidify the cause-and-effect evidence that exercise protects against heart disease and averts premature mortality.

Short-term benefits of catch-up growth for small-for-gestational-age infants

Abstract: Background Recent studies suggest that small newborns who present rapid postnatal growth may have an increased risk of chronic diseases in adulthood. On the other hand, it is widely assumed that catch-up growth is desirable for low birthweight children, but the literature on this subject is limited. Methods Population-based cohort study in southern Brazil, with 3582 children examined at birth, 20 and 42 months of age. Catch-up growth from 0 to 20 months was related to subsequent risks of hospital admissions and mortality. Results Children who were small-for-gestational-age (SGA) but presented substantial weight gain (>0.66 z-score) up to the age of 20 months had 65% fewer subsequent hospital admissions than other SGA children (5.6% versus 16.0%; P , 0.001). Mortality to age 5 years was 75% lower (3 versus 13 per 1000, a non-significant difference based on a small number of deaths) for rapid-growing SGA children compared to the remaining SGA children. Their admission and mortality rates were similar to those observed for children born with an appropriate birthweight for their gestational age (AGA). Similar positive effects of rapid growth were found for AGA children. Conclusion There appear to be definite benefits associated with catch-up growth. Growth promotion efforts for infants who are born small should take into account their possible short- and long-term consequences.

Case-control study of parental age, parity and socioeconomic level in relation to childhood cancers

Abstract: Background Parental ages, parity, and social class have been found in some studies to be associated with particular childhood cancers. Further investigation is warranted because of conflicting findings, biases, and the need to test specific hypotheses. Methods A case-control study was conducted (England and Wales, ages 0-14 years). Cases were ascertained from the National Registry of Childhood Tumours, and were born and diagnosed during 1968-1986. Birth record controls were matched 1:1 to cases on date of birth, sex and area. Information on variables of interest for both groups came from birth records. In all, 10 162 pairs could contribute to matched analyses. Results The odds ratio (OR) for retinoblastoma resulting from assumed new germ cell mutations among children of fathers aged ≥45 years was 3.0 (95% CI: 0.2-41.7). The risk of childhood acute lymphoblastic leukaemia (ALL) was significantly higher among children of older mothers and fathers, and significant trends with increasing mothers' (P < 0.001) and fathers' (P 0.002) ages were found. There was a strong and significant protective effect of increasing parity on risk of childhood ALL. The adjusted OR for parity of ≥5 (versus 0) was 0.5 (95% CI: 0.3-0.8). Children in more deprived communities had a lower risk of ALL; but this was not significant after confounders were allowed for. There was no significant effect of social class based on parental occupation on ALL risk, but the numbers were small in those analyses. Conclusions The associations between ALL and parental ages did not disappear when children with Down syndrome were excluded, suggesting an additional explanation beyond known links. The strong ALL association with parity may be because of an unknown environmental risk factor.

Risk factors and incident coronary heart disease in Chinese, Malay and Asian Indian males: the Singapore Cardiovascular Cohort Study

Abstract: OBJECTIVE This prospective study in Singapore investigated the relationships of established coronary risk factors with incident coronary heart disease (CHD) for Chinese, Malay, and Asian Indian males. SUBJECTS A cohort (consisting of 2879 males without diagnosed CHD) derived from three previous cross-sectional surveys. METHODS Individual baseline data were linked to registry databases to obtain the first event of CHD. Hazard ratios (HR) or relative risks for risk factors were calculated using Cox's proportional hazards model with adjustment for age and ethnic group and adjustment for age, ethnic group and all other risk factors (overall adjusted). RESULTS There were 24,986 person-years of follow-up. The overall adjusted HR with 95% CI are presented here. Asian Indians were at greatest risk of CHD, compared to Chinese (3.0; 2.0-4.8) and Malays (3.4; 1.9-3.3). Individuals with hypertension (2.4; 1.6-2.7) or diabetes (1.7; 1.1-2.7) showed a higher risk of CHD. High low density lipoprotein cholesterol (LDL-C) (1.5; 1.0-2.1), high fasting triglyceride (1.5; 0.9-2.6) and low high density lipoprotein cholesterol (HDL-C) (1.3; 0.9-2.0) showed a lesser but still increased risk. Alcohol intake was protective with non-drinkers having an increased risk of CHD (1.8; 1.0-3.3). Obesity (body mass index > or =30) showed an increased risk (1.8; 0.6-5.4). An increased risk of CHD was found in cigarette smokers of > or =20 pack years (1.5; 0.9-2.5) but not with lesser amounts. CONCLUSIONS The increased susceptibility of Asian Indian males to CHD has been confirmed in a longitudinal study. All of the examined established risk factors for CHD were found to play important but varying roles in the ethnic groups in Singapore.

The validity of self-reported use of health care across socioeconomic strata: a comparison of survey and registration data

Abstract: Background. Socioeconomic differences in health and in use of health care are well known. Most data on socioeconomic differences in health care utilization are based on retrospective self-report in community surveys, but the evidence on the validity of self-reported utilization of health care across socioeconomic groups is limited. The aim of this study was to assess the validity of self-reported utilization of health care across socioeconomic groups in the general population. Methods. We compared the concordance of self-reported and registered hospitalization (one year, n = 1277), and utilization of physiotherapy (one year, n = 1302) and use of prescription drugs (3 months, n = 899), by socioeconomic group (educational level, income, occupational status). Data came from a face-to-face health interview survey in Amsterdam and a health insurance register, and were limited to native Dutch and lower and middle income groups. Results. Concordance between reported and registered utilization was generally good to excellent; kappas (agreement adjusted for chance agreement) and percentage accurately reporting ranged from 0.60 and 80% (drugs) to 0.80 and 96% (hospitalization). They differed little, and without statistical significance, between people of low socioeconomic status and others. Assessment of socioeconomic groups in more detail yields somewhat more variation, but no systematic trend in concordance by higher socioeconomic status. Conclusion. Self-report offers a reasonably valid estimate of differences in utilization of health care between socioeconomic groups in the general population, at least for lower and middle income groups.

Temperature, housing, deprivation and their relationship to excess winter mortality in Great Britain, 1986–1996

Abstract: OBJECTIVES To examine the associations between temperature, housing, deprivation and excess winter mortality using census variables as proxies for housing conditions. DESIGN Small area ecological study at electoral ward level. Setting Great Britain between 1986 and 1996. PARTICIPANTS Men and women aged 65 and over. MAIN OUTCOME MEASURES Deaths from all causes (International Classification of Diseases, Ninth Revision [ICD-9] codes 0-999), coronary heart disease (ICD-9 410-414), stroke (ICD-9 430-438) and respiratory diseases (ICD-9 460-519). Odds of death occurring in winter period of the four months December to March compared to the rest of the year. RESULTS During the study period (excluding the influenza epidemic year of 1989/90), a total of 1,682,687 deaths occurred in winter and 2,825,223 deaths occurred during the rest of the year among people aged > or =65 (around 30,000 excess winter deaths per year). A trend of higher excess winter mortality with age was apparent across all disease categories (P < 0.01). There was a significant association between winter mortality and temperature with a 1.5% higher odds of dying in winter for every 1 degrees C reduction in 24-h mean winter temperature. The amount of rain, wind and hours of sunshine were inversely associated with excess winter mortality. Selected housing variables derived from the English House Condition Survey showed little agreement with census-derived variables at electoral ward level. For all-cause mortality there was little association between deprivation and excess winter mortality, although lack of central heating was associated with a higher risk of dying in winter (odds ratio [OR] = 1.016, 95% CI : 1.009-1.022). CONCLUSIONS Excess winter mortality continues to be an important public health problem in Great Britain. There was a strong inverse association with temperature. Lack of central heating was associated with higher excess winter mortality. Further work is needed to disentangle the complex relationships between different indicators of housing quality and other measures of socioeconomic deprivation and their relationship to the high number of excess winter deaths in Great Britain.

The methodological quality of randomized controlled trials of homeopathy, herbal medicines and acupuncture

Abstract: BACKGROUND To investigate the methodological quality of randomized controlled trials in three areas of complementary medicine. METHODS The methodological quality of 207 randomized trials collected for five previously published systematic reviews on homeopathy, herbal medicine (Hypericum for depression, Echinacea for common cold), and acupuncture (for asthma and chronic headache) was assessed using a validated scale (the Jadad scale) and single quality items. RESULTS While the methodological quality of the trials was highly variable, the majority had important shortcomings in reporting and/or methodology. Major problems in most trials were the description of allocation concealment and the reporting of drop-outs and withdrawals. There were relevant differences in single quality components between the different complementary therapies: For example, acupuncture trials reported adequate allocation concealment less often (6% versus 32% of homeopathy and 26% of herb trials), and trials on herbal extracts had better summary scores (mean score 3.12 versus 2.33 for homeopathy and 2.19 for acupuncture trials). Larger trials published more recently in journals listed in Medline and in English language scored significantly higher than trials not meeting these criteria. CONCLUSION Trials of complementary therapies often have relevant methodological weaknesses. The type of weaknesses varies considerably across interventions.

Women's exposure to early and later life socioeconomic disadvantage and coronary heart disease risk: the Stockholm Female Coronary Risk Study

Abstract: Background Measures of low socioeconomic position have been associated with increased risk for coronary heart disease (CHD) among women. A more complete understanding of this association is gained when socioeconomic position is conceptualized from a life course perspective where socioeconomic position is measured both in early and later life. We examined various life course socioeconomic indicators in relation to CHD risk among women. Methods The Stockholm Female Coronary Risk Study is a population-based case-control study, in which 292 women with CHD aged <65 years and 292 age-matched controls were investigated using a wide range of socioeconomic, behavioural, psychosocial and physiological risk factors. Socioeconomic disadvantage in early life (large family size in childhood, being born last, low education), and in later life (housewife or blue-collar occupation at labour force entry, blue-collar occupation at examination, economic hardships prior to examination) was assessed. Results Exposure to early (OR = 2.65, 95% CI : 1.12‐6.54) or later (OR = 5.38, 95% CI : 2.01‐11.43) life socioeconomic disadvantage was associated with increased CHD risk as compared to not being exposed. After simultaneous adjustment for marital status and traditional CHD risk factors, early and later socioeconomic disadvantage, exposure to three instances of socioeconomic disadvantage in early life was associated with an increased CHD risk of 2.48 (95% CI : 0.90‐6.83) as compared to not being exposed to any disadvantage. The corresponding adjusted risk associated with exposure to later life disadvantage was 3.22 (95% CI : 1.02‐10.53). Further analyses did not show statistical evidence of interaction effects between early and later life exposures (P = 0.12), although being exposed to both resulted in a 4.2-fold (95% CI : 1.4‐12.1) increased CHD risk. Exposure to cumulative socioeconomic disadvantage (combining both early and later life), across all stages in the life course showed strong, graded associations with CHD risk after adjusting for traditional CHD risk factors. Stratification of cumulative disadvantage by body height showed that exposure to more than three periods of cumulative socioeconomic disadvantage had a 1.7- (95% CI : 0.9‐3.2) and 1.9(95% CI : 1.0‐7.7) fold increased CHD risk for taller and shorter women, respectively. The combination of both short stature and more than two periods of cumulative socioeconomic disadvantage resulted in a 4.4-fold (95% CI : 1.7‐9.3) increased CHD risk.

Trends in coronary risk factors in the WHO MONICA Project

Abstract: d The World Health Organization (WHO) MONICA Project was established to determine how trends in event rates for coronary heart disease (CHD) and, optionally, stroke were related to trends in classic coronary risk factors. Risk factors were therefore monitored over ten years across 38 populations from 21 countries in four continents (overall period covered: 1979-1996). A standard protocol was applied across participating centres, in at least two, and usually three, independent surveys conducted on random samples of the study populations, well separated within the 10-year study period. Smoking rates decreased in most male populations (35-64 years) but in females the majority showed increases. Systolic blood pressure showed decreasing trends in the majority of centres in both sexes. Mean levels of cholesterol generally showed downward trends, which, although the changes were small, had large effects on risk. There was a trend of increasing body mass index (BMI) with half the female populations and two-thirds of the male populations showing a significant increase. s It is feasible to monitor the classic CHD risk factors in diverse populations through repeated surveys over a decade. In general, the risk factor trends are downwards in most populations but in particular, an increase in smoking in women in many populations and increasing BMI, especially in men, are worrying findings with significant public health implications.

Early childhood diarrhoea and helminthiases associate with long-term linear growth faltering

Abstract: Background Although the acute mortality from diarrhoeal diseases is well recognized, the potentially prolonged impact of early childhood diarrhoea on background growth and development is often overlooked. To examine the magnitude and duration of the association of early childhood enteric infections with growth faltering in later childhood, we investigated associations of early childhood diarrhoea (0-2 years) and intestinal helminthiases with nutritional status from age 2 to 7 years. Methods Twice-weekly diarrhoea surveillance and quarterly anthropometrics were followed from 1989 to 1998 in 119 children born into a Northeast Brazilian shantytown. Results Diarrhoea burdens at 0-2 years old were significantly associated with growth faltering at ages 2-7 years, even after controlling for nutritional status in infancy, helminthiases at 0-2 years old, family income, and maternal education by Pearson correlation, multivariate linear regression, and repeat measures analysis. The average 9.1 diarrhoeal episodes before age 2 years was associated with a 3.6 cm (95% CI : 0.6-6.6 cm) growth shortfall at age 7 years. Early childhood helminthiasis was also associated with linear growth faltering and a further 4.6 cm shortfall (95% CI : 0.8-7.9 cm) at age 7 years. Conclusions Early childhood diarrhoea and helminthiases independently associate with substantial linear growth shortfalls that continue beyond age 6 years. Targeted interventions for their control may have profound and lasting growth benefits for children in similar settings.