Showing papers by "Frank E. Speizer published in 1985"

Reproducibility and validity of a semiquantitative food frequency questionnaire

Abstract: The aim of this study was to evaluate the reproducibility and validity of a 61-item semiquantitative food frequency questionnaire used in a large prospective study among women. This form was administered twice to 173 participants at an interval of approximately one year (1980-1981), and four one-week diet records for each subject were collected during that period. Intraclass correlation coefficients for nutrient intakes estimated by the one-week diet records (range = 0.41 for total vitamin A without supplements to 0.79 for vitamin B6 with supplements) were similar to those computed from the questionnaire (range = 0.49 for total vitamin A without supplements to 0.71 for sucrose), indicating that these methods were generally comparable with respect to reproducibility. With the exception of sucrose and total carbohydrate, nutrient intakes from the diet records tended to correlate more strongly with those computed from the questionnaire after adjustment for total caloric intake. Correlation coefficients between the mean calorie-adjusted intakes from the four one-week diet records and those from the questionnaire completed after the diet records ranged from 0.36 for vitamin A without supplements to 0.75 for vitamin C with supplements. Overall, 48% of subjects in the lowest quintile of calorie-adjusted intake computed from the diet records were also in the lowest questionnaire quintile, and 74% were in the lowest one of two questionnaire quintiles. Similarly, 49% of those in the highest diet record quintile were also in the highest questionnaire quintile, and 77% were in the highest one or two questionnaire quintiles. These data indicate that a simple self-administered dietary questionnaire can provide useful information about individual nutrient intakes over a one-year period.

A Prospective Study of Postmenopausal Estrogen Therapy and Coronary Heart Disease

Abstract: To clarify the possible role of postmenopausal estrogen use in coronary heart disease, we surveyed 121,964 female nurses, aged 30 to 55 years, with mailed questionnaires, beginning in 1976. Information on hormone use and other potential risk factors was updated and the incidence of coronary heart disease was ascertained through additional questionnaires in 1978 and 1980, with a 92.7 per cent follow-up. End points were documented by medical records. During 105,786 person-years of observation among 32,317 postmenopausal women who were initially free of coronary disease, 90 women had either nonfatal myocardial infarctions (65 cases) or fatal coronary heart disease (25 cases). As compared with the risk in women who had never used postmenopausal hormones, the age-adjusted relative risk of coronary disease in those who had ever used them was 0.5 (95 per cent confidence limits, 0.3 and 0.8; P = 0.007), and the risk in current users was 0.3 (95 per cent confidence limits, 0.2 and 0.6; P = 0.001). The relative risks were similar for fatal and nonfatal disease and were unaltered after adjustment for cigarette smoking, hypertension, diabetes, high cholesterol levels, a parental history of myocardial infarction, past use of oral contraceptives, and obesity. These data support the hypothesis that the postmenopausal use of estrogen reduces the risk of severe coronary heart disease.

Relative weight and risk of breast cancer among premenopausal women

Abstract: Although higher relative weight is generally considered to increase the risk of breast cancer, several case-control studies have suggested that the reverse may be true among premenopausal women The association between Quetelet's index (a measure of relative weight calculated as weight/height) and the subsequent incidence of breast cancer was therefore examined during four years of follow-up among a cohort of 121,964 US women who were 30-55 years of age in 1976 In contrast to women who had experienced natural menopause or bilateral oophorectomy, the incidence of breast cancer among premenopausal women decreased with higher levels of relative weight Age-adjusted relative risks for increasing quintiles of Quetelet's index were 100, 090, 090, 073, and 066 (Mantel extension test for trend = -282, p = 0005) This inverse association was not explained by known risk factors for breast cancer and was somewhat stronger when Quetelet's index was computed using reported weight at age 18 years The excess incidence of breast cancer among lean premenopausal women, however, was limited to tumors that were less than 20 cm in diameter, were not associated with metastases to lymph nodes, and were well-differentiated These findings suggest that the apparent excess risk of breast cancer among lean premenopausal women may result at least in part from easier, and thus earlier, diagnosis of less aggressive tumors

Distribution of forced expiratory volume in one second and forced vital capacity in healthy, white, adult never-smokers in six U.S. cities.

Abstract: As part of a longitudinal study of the respiratory health effects of air pollution, we measured the lung function of 2,454 white adults 25 to 74 yr of age who had never smoked and who reported no respiratory symptoms These measurements were analyzed to develop a simple model for the cross-sectional dependence of pulmonary function on height, sex, and age Both forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) can be effectively standardized for body size by dividing each pulmonary function measurement by the square of the standing height (HT2) The age-specific distribution of these standardized measurements is approximately Gaussian, with variance that is independent of age Plots of FEV1/HT2 and FVC/HT2 against age showed a nonlinear relationship consistent with an increase in the rate of pulmonary function loss with age On the basis of these graphic analyses, both pulmonary function measurements were fitted to a four-parameter normative model including sex and linear and quadratic terms in age as dependent variables This model gave predictions that were very close to those from more complicated models currently in use Predicted percentile levels were calculated for each sex and age, and shown to describe the observations well The estimated annual change in height-standardized lung function based on the cross-sectional model was compared with the observed change between the first and second examinations of these adults 3 yr later The observed changes were close to predicted values, except for subjects younger than 35 yr of age at their first examination The observed change was larger for men than for women Such simple longitudinal comparisons are subject to selection bias In this study, subjects in the lowest quartile of FEV1/HT2 for their age and sex at the first examination had a lower probability of providing a lung function measurement 3 yr later

The relationship of respiratory infections in early childhood to the occurrence of increased levels of bronchial responsiveness and atopy.

Abstract: We assessed the relationship of antecedent acute respiratory illness to the occurrence of airway responsiveness and atopy in a population-based cohort of 194 children 12 to 16 yr of age from East Boston, Massachusetts. A history of croup or bronchiolitis as reported by their parents was determined at study onset when the children were 5 to 9 yr of age. During the second and third years of the study, acute respiratory illness was assessed. Five years after the prospective respiratory illness assessment, airway responsiveness was evaluated with eucapneic hyperpnea to subfreezing air, and atopy was evaluated with skin tests to 4 environmental antigens. Both a prior history of croup of bronchiolitis (OR = 2.29, p = 0.04) and greater than 2 acute lower respiratory illnesses (OR = 3.72, p = 0.012) were associated with increased levels of airway responsiveness. Neither index of respiratory illness experience was related to the presence of atopy. However, maternal cigarette smoking was significantly associated wi...

Effect of cigarette smoking on the pulmonary function of children and adolescents.

Abstract: The effect of personal cigarette smoking on the growth of lung function in children and adolescents has been assessed in a longitudinal study of a group of 669 subjects 5 to 19 yr of age at initial examination. Subjects were seen annually and assessed with standard questionnaires and measurements of forced expiratory volume in one second (FEV1) and forced expiratory flow during the middle half of the forced vital capacity (FEF25-75). Multiple regression analysis revealed that after correction for previous FEV1 or FEF25-75, age, sex, height, change in height, interactions of age and change in height, and sex and height, and mother's smoking, the personal smoking by the children led to a significant decrease in the rate of growth of FEV1 (p less than 0.001) and FEF25-75 (p = 0.033). On the basis of this analysis, it is estimated that, on average, children who begin to smoke at 15 yr of age and continue to smoke would achieve only 92% (95% confidence limit, 87 to 96%) of their expected FEV1 and 90% (95% confidence limit, 81 to 99%), of their expected FEF25-75 at 20 yr of age. These data suggest that relatively small amounts of cigarette use (median total consumption of 7,300 cigarettes in this study) by adolescents can lead to significant effects on the growth of lung function.

The use of an autoregressive model for the analysis of longitudinal data in epidemiologic studies

Abstract: Korn and Whittemore1,2 have presented methods for analyzing longitudinal data where the number of observations per individual is large relative to the number of variables considered for each subject. However, this is often not the case in epidemiologic studies, since one usually collects data at relatively few time points, and the quantity of data collected for each individual at each time point is typically extensive. We present here an autoregressive model for analyzing longitudinal data of this type for the case of a continuous outcome variable. Some of the important features of this model are that one can (1) in the same analysis, consider both independent variables that are time-dependent and those that are fixed over time, (2) partially use data for an individual where some examinations are missing, (3) assess relationships between changes in outcome and exposure over short periods of time, (4) use ordinary multiple regression methods. Anderson3 has considered this type of model, but, to our knowledge, the model has never been applied to biostatistical problems. We illustrate these methods with data from a longitudinal study that seeks to identify the role of personal cigarette smoking on changes in pulmonary function in children.

Effects of ozone on the pulmonary function of children

Abstract: Healthy active children, 7 to 13 years old, in a summer recreational camp were chosen as subjects to investigate the acute effects of exposure to ambient-air pollution. Pulmonary-function tests were administered at the camp on 16 days during a five week period in 1982. Ambient-air-pollution data were collected approximately 6 km from the camp. For each of the 39 children tested on six or more days, a linear regression was calculated between the peak one-hour ozone concentration for a given day and each of three functional parameters determined for the same day from the spirograms: forced vital capacity (FVC), Forced expiratory volume in 1 second (PEV1), and peak expiratory flow rate (PEFR). All mean slopes were negative, except for FVC in boys, indicating a general tendency for decreased function with increasing ozone concentration; however only PEFR mean slopes for girls and for all subjects were statistically significantly different from zero. For each of 49 children seen on four or more days, a summary weighted correlation coefficient between peak ozone level and each of the three pulmonary function parameters was calculated. As in the regression analysis, decrements in PEFR were significantly correlated with the ozone exposure. Overall, the decrements were small,more » approximately a 10% decrease in PEFR with an ozone exposure level of 120 ppb.« less

Effects of passive smoking on health of children

Abstract: Analysis of data on the effects of passive smoking obtained in preadolescent children from the Harvard Six-Cities Study demonstrates an exposure-response relationship between the number of smokers in the household and the reporting rates for doctor-diagnosed respiratory illness before age 2, history of bronchitis, wheeze most days and nights apart from colds, and a composite of symptoms defined as the lower respiratory index. Similarly, when only the amount currently smoked by the mother was used, the data indicated a relatively uniform increase in each of the reported diseases and symptoms. FEV1 was lower in children with smoking mothers compared to children of nonsmoking mothers. Rate of increases in FEV1 after adjusting for normal growth was significantly smaller in children of smoking mothers and was related also to amount smoked. Notably the effect on level of FVC was not seen and this finding, consistent in several studies, remains unexplained. Although children of smoking mothers were shorter on the average than children of nonsmoking mothers, no on-going passive smoking effect on height growth can be ascertained. All these differences are small and their medical significance remains to be defined.

Ozone and photochemical pollutants. Status after 25 years.

Abstract: Data related to the health effects of air pollution are discussed in this editorial. Three kinds of studies - animal experimentation, controlled chamber experiments in both animals and humans and population-based epidemiological investigations are reported from a seminar held at the University of California, Davis. Each is summarized as to whether it proved to be a health effect for ozone or NO/sub 2/. The role of physicians in the interpretation of the data and in public policy decision-making is examined.