Showing papers in "American Journal of Epidemiology in 2013"

Increased Prevalence of Sleep-Disordered Breathing in Adults

Abstract: Sleep-disordered breathing is a common disorder with a range of harmful sequelae. Obesity is a strong causal factor for sleep-disordered breathing, and because of the ongoing obesity epidemic, previous estimates of sleep-disordered breathing prevalence require updating. We estimated the prevalence of sleep-disordered breathing in the United States for the periods of 1988–1994 and 2007–2010 using data from the Wisconsin Sleep Cohort Study, an ongoing community-based study that was established in 1988 with participants randomly selected from an employed population of Wisconsin adults. A total of 1,520 participants who were 30–70 years of age had baseline polysomnography studies to assess the presence of sleep-disordered breathing. Participants were invited for repeat studies at 4-year intervals. The prevalence of sleep-disordered breathing was modeled as a function of age, sex, and body mass index, and estimates were extrapolated to US body mass index distributions estimated using data from the National Health and Nutrition Examination Survey. The current prevalence estimates of moderate to severe sleep-disordered breathing (apnea-hypopnea index, measured as events/hour, ≥15) are 10% (95% confidence interval (CI): 7, 12) among 30–49-year-old men; 17% (95% CI: 15, 21) among 50–70-year-old men; 3% (95% CI: 2, 4) among 30–49-year-old women; and 9% (95% CI: 7, 11) among 50–70 year-old women. These estimated prevalence rates represent substantial increases over the last 2 decades (relative increases of between 14% and 55% depending on the subgroup).

A New Framework and Software to Estimate Time-Varying Reproduction Numbers During Epidemics

Abstract: The quantification of transmissibility during epidemics is essential to designing and adjusting public health responses. Transmissibility can be measured by the reproduction number R, the average number of secondary cases caused by an infected individual. Several methods have been proposed to estimate R over the course of an epidemic; however, they are usually difficult to implement for people without a strong background in statistical modeling. Here, we present a ready-to-use tool for estimating R from incidence time series, which is implemented in popular software including Microsoft Excel (Microsoft Corporation, Redmond, Washington). This tool produces novel, statistically robust analytical estimates of R and incorporates uncertainty in the distribution of the serial interval (the time between the onset of symptoms in a primary case and the onset of symptoms in secondary cases). We applied the method to 5 historical outbreaks; the resulting estimates of R are consistent with those presented in the literature. This tool should help epidemiologists quantify temporal changes in the transmission intensity of future epidemics by using surveillance data.

Prevalence of Nonalcoholic Fatty Liver Disease in the United States: The Third National Health and Nutrition Examination Survey, 1988–1994

Abstract: In the United States, the burden of liver-related diseases is important. Over the last 2 decades, liver-related mortality ranked among the top 12 causes of death, and among adults aged 45–54 years, it has been repeatedly listed as the fourth leading cause of death (1, 2). Nonalcoholic fatty liver disease (NAFLD) is thought to be the most common chronic liver disease in the Western world (3–5). However, US estimates of the prevalence of NAFLD are lacking, and previous nationally representative studies have been limited by the use of surrogate markers of liver disease, namely liver enzymes, with estimates in the range of 3%–23% (6–9). Studies that have used more sensitive, specific, or direct methods have been limited by small sample size or by the use of convenience samples and report a range in the prevalence of NAFLD (19%–46%) (10, 11). Although the “gold standard” for diagnosing and staging NAFLD is histology, abdominal unltrasonography allows its detection (4, 5). NAFLD was traditionally thought to be a benign condition; however, longitudinal studies have shown that it can progress to nonalcoholic steatohepatitis and fibrosis (12–14), leading to cirrhosis (15, 16). Also, there is increasing evidence suggesting that NAFLD may play a significant role in the strong association between obesity and the development of liver cancer (17, 18). Large, population-based estimates of the prevalence of NAFLD as detected by ultrasonography are available for other Western and non-Western countries and show that its prevalence parallels that of obesity (11). For the United States, there are no representative data regarding the prevalence and epidemiology of this condition. These estimates are key to assessing the magnitude of the disease and planning and projecting the health-care costs and the burden associated with liver disease. The Third National Health and Nutrition Examination Survey (NHANES III) was a large and representative survey of the noninstitutionalized US civilian population; it included gallbladder ultrasonography of all participants aged 20–74 years. Recently, we reevaluated these ultrasonography videotapes to assess the presence of hepatic steatosis. By using these ultrasonography data, our aims were 1) to estimate the prevalence of any hepatic steatosis and NAFLD in the United States by key sociodemographic characteristics and 2) to examine metabolic, anthropometric, and laboratory correlates of hepatic steatosis and NAFLD.

The Table 2 Fallacy: Presenting and Interpreting Confounder and Modifier Coefficients

Abstract: It is common to present multiple adjusted effect estimates from a single model in a single table. For example, a table might show odds ratios for one or more exposures and also for several confounders from a single logistic regression. This can lead to mistaken interpretations of these estimates. We use causal diagrams to display the sources of the problems. Presentation of exposure and confounder effect estimates from a single model may lead to several interpretative difficulties, inviting confusion of direct-effect estimates with total-effect estimates for covariates in the model. These effect estimates may also be confounded even though the effect estimate for the main exposure is not confounded. Interpretation of these effect estimates is further complicated by heterogeneity (variation, modification) of the exposure effect measure across covariate levels. We offer suggestions to limit potential misunderstandings when multiple effect estimates are presented, including precise distinction between total and direct effect measures from a single model, and use of multiple models tailored to yield total-effect estimates for covariates.

Efficient Design for Mendelian Randomization Studies: Subsample and 2-Sample Instrumental Variable Estimators

Abstract: Mendelian randomization (MR) is a method for estimating the causal relationship between an exposure and an outcome using a genetic factor as an instrumental variable (IV) for the exposure. In the traditional MR setting, data on the IV, exposure, and outcome are available for all participants. However, obtaining complete exposure data may be difficult in some settings, due to high measurement costs or lack of appropriate biospecimens. We used simulated data sets to assess statistical power and bias for MR when exposure data are available for a subset (or an independent set) of participants. We show that obtaining exposure data for a subset of participants is a cost-efficient strategy, often having negligible effects on power in comparison with a traditional complete-data analysis. The size of the subset needed to achieve maximum power depends on IV strength, and maximum power is approximately equal to the power of traditional IV estimators. Weak IVs are shown to lead to bias towards the null when the subsample is small and towards the confounded association when the subset is relatively large. Various approaches for confidence interval calculation are considered. These results have important implications for reducing the costs and increasing the feasibility of MR studies.

Factors Related to Age at Natural Menopause: Longitudinal Analyses From SWAN

Abstract: Early age at the natural final menstrual period (FMP) or menopause has been associated with numerous health outcomes and might be a marker of future ill health. However, potentially modifiable factors affecting age at menopause have not been examined longitudinally in large, diverse populations. The Study of Women’s Health Across the Nation (SWAN) followed 3,302 initially premenopausal and early perimenopausal women from 7 US sites and 5 racial/ethnic groups, using annual data (1996–2007) and Cox proportional hazards models to assess the relation of time-invariant and time-varying sociodemographic, lifestyle, and health factors to age at natural FMP. Median age at the FMP was 52.54 years (n= 1,483 observed natural FMPs). Controlling for sociodemographic, lifestyle, and health factors, we found that racial/ethnic groups did not differ in age at the FMP. Higher educational level, prior oral contraceptive use, and higher weight at baseline, as well as being employed, not smoking, consuming alcohol, having less physical activity, and having better self-rated health over follow-up, were significantly associated with later age at the FMP. These results suggest that age at the natural FMP reflects a complex interrelation of health and socioeconomic factors, which could partially explain the relation of late age at FMP to reduced morbidity and mortality.

Evidence on Vulnerability and Susceptibility to Health Risks Associated With Short-Term Exposure to Particulate Matter: A Systematic Review and Meta-Analysis

Abstract: Although there is strong evidence that short-term exposure to particulate matter is associated with health risks, less is known about whether some subpopulations face higher risks. We identified 108 papers published after 1995 and summarized the scientific evidence regarding effect modification of associations between short-term exposure to particulate matter and the risk of death or hospitalization. We performed a meta-analysis of estimated mortality associations by age and sex. We found strong, consistent evidence that the elderly experience higher risk of particular matter--associated hospitalization and death, weak evidence that women have higher risks of hospitalization and death, and suggestive evidence that those with lower education, income, or employment status have higher risk of death. Meta-analysis showed a statistically higher risk of death of 0.64% (95% confidence interval (CI): 0.50, 0.78) for older populations compared with 0.34% (95% CI: 0.25, 0.42) for younger populations per 10 μg/m3 increase of particulate matter with aerodynamic diameter ≤10 μm. Women had a slightly higher risk of death of 0.55% (95% CI: 0.41, 0.70) compared with 0.50% (95% CI: 0.34, 0.54) for men, but these 2 risks were not statistically different. Our synthesis on modifiers for risks associated with particulate matter can aid the design of air quality policies and suggest directions for future research. Studies of biological mechanisms could be informed by evidence of differential risks by population, such as by sex and preexisting conditions.

Personality and all-cause mortality: individual-participant meta-analysis of 3,947 deaths in 76,150 adults

Abstract: Personality may influence the risk of death, but the evidence remains inconsistent. We examined associations between personality traits of the five-factor model (extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience) and the risk of death from all causes through individual-participant meta-analysis of 76,150 participants from 7 cohorts (the British Household Panel Survey, 2006-2009; the German Socio-Economic Panel Study, 2005-2010; the Household, Income and Labour Dynamics in Australia Survey, 2006-2010; the US Health and Retirement Study, 2006-2010; the Midlife in the United States Study, 1995-2004; and the Wisconsin Longitudinal Study's graduate and sibling samples, 1993-2009). During 444,770 person-years at risk, 3,947 participants (54.4% women) died (mean age at baseline = 50.9 years; mean follow-up = 5.9 years). Only low conscientiousness-reflecting low persistence, poor self-control, and lack of long-term planning-was associated with elevated mortality risk when taking into account age, sex, ethnicity/nationality, and all 5 personality traits. Individuals in the lowest tertile of conscientiousness had a 1.4 times higher risk of death (hazard ratio = 1.37, 95% confidence interval: 1.18, 1.58) compared with individuals in the top 2 tertiles. This association remained after further adjustment for health behaviors, marital status, and education. In conclusion, of the higher-order personality traits measured by the five-factor model, only conscientiousness appears to be related to mortality risk across populations.

Estimating 24-Hour Urinary Sodium Excretion From Casual Urinary Sodium Concentrations in Western Populations The INTERSALT Study

Abstract: High intakes of dietary sodium are associated with elevated blood pressure levels and an increased risk of cardiovascular disease. National and international guidelines recommend reduced sodium intake in the general population, which necessitates population-wide surveillance. We assessed the utility of casual (spot) urine specimens in estimating 24-hour urinary sodium excretion as a marker of sodium intake in the International Cooperative Study on Salt, Other Factors, and Blood Pressure. There were 5,693 participants recruited in 1984–1987 at the ages of 20–59 years from 29 North American and European samples. Participants were randomly assigned to test or validation data sets. Equations derived from casual urinary sodium concentration and other variables in the test data were applied to the validation data set. Correlations between observed and estimated 24-hour sodium excretion were 0.50 for individual men and 0.51 for individual women; the values were 0.79 and 0.71, respectively, for population samples. Bias in mean values (observed minus estimated) was small; for men and women, the values were −1.6 mmol per 24 hours and 2.3 mmol per 24 hours, respectively, at the individual level and −1.8 mmol per 24 hours and 2.2 mmol per 24 hours, respectively, at the population level. Proportions of individuals with urinary 24-hour sodium excretion above the recommended levels were slightly overestimated by the models. Casual urine specimens may be a useful, low-burden, low-cost alternative to 24-hour urine collections for estimation of population sodium intakes; ongoing calibration with study-specific 24-hour urinary collections is recommended to increase validity.

Cigarette, Cigar, and Pipe Smoking and the Risk of Head and Neck Cancers: Pooled Analysis in the International Head and Neck Cancer Epidemiology Consortium

Abstract: Cigar and pipe smoking are considered risk factors for head and neck cancers, but the magnitude of effect estimates for these products has been imprecisely estimated. By using pooled data from the International Head and Neck Cancer Epidemiology (INHANCE) Consortium (comprising 13,935 cases and 18,691 controls in 19 studies from 1981 to 2007), we applied hierarchical logistic regression to more precisely estimate odds ratios and 95% confidence intervals for cigarette, cigar, and pipe smoking separately, compared with reference groups of those who had never smoked each single product. Odds ratios for cigar and pipe smoking were stratified by ever cigarette smoking. We also considered effect estimates of smoking a single product exclusively versus never having smoked any product (reference group). Among never cigarette smokers, the odds ratio for ever cigar smoking was 2.54 (95% confidence interval (CI): 1.93, 3.34), and the odds ratio for ever pipe smoking was 2.08 (95% CI: 1.55, 2.81). These odds ratios increased with increasing frequency and duration of smoking (Ptrend ≤ 0.0001). Odds ratios for cigar and pipe smoking were not elevated among ever cigarette smokers. Head and neck cancer risk was elevated for those who reported exclusive cigar smoking (odds ratio = 3.49, 95% CI: 2.58, 4.73) or exclusive pipe smoking (odds ratio = 3.71, 95% CI: 2.59, 5.33). These results suggest that cigar and pipe smoking are independently associated with increased risk of head and neck cancers.

Association of Injurious Falls With Disability Outcomes and Nursing Home Admissions in Community-Living Older Persons

Abstract: Little is known about the deleterious effects of injurious falls relative to those of other disabling conditions or whether these effects are driven largely by hip fractures. From a cohort of 754 community-living elders of New Haven, Connecticut, we matched 122 hospitalizations for an injurious fall (59 hip-fracture and 63 other fall-related injuries) to 241 non-fall-related hospitalizations. Participants (mean age: 85.7 years) were evaluated monthly for disability in 13 activities and admission to a nursing home from 1998 to 2010. For both hip-fracture and other fall-related injuries, the disability scores were significantly greater during each of the first 6 months after hospitalization than for the non-fall-related admissions, with adjusted risk ratios at 6 months of 1.5 (95% confidence interval (CI): 1.3, 1.7) for hip fracture and 1.4 (95% CI: 1.2, 1.6) for other fall-related injuries. The likelihood of having a long-term nursing home admission was considerably greater after hospitalization for a hip fracture and other fall-related injury than for a non-fall-related reason, with adjusted odds ratios of 3.3 (95% CI: 1.3, 8.3) and 3.2 (95% CI: 1.3, 7.8), respectively. Relative to other conditions leading to hospitalization, hip-fracture and other fall-related injuries are associated with worse disability outcomes and a higher likelihood of long-term nursing home admissions.

Use of Azathioprine and the Risk of Cancer in Inflammatory Bowel Disease

Abstract: Increased risks of lymphoma and skin cancer associated with thiopurine use among patients with inflammatory bowel disease have been shown, but data on the overall cancer risk are limited. We conducted a historical cohort study of 45,986 patients with inflammatory bowel disease (of whom, 5,197 (11%) used azathioprine) in Denmark from 1997 to 2008. We linked registry data on filled drug prescriptions, cancer diagnoses, and covariates and compared rates of overall incident cancer and cancer subgroups between users and nonusers of azathioprine, adjusting for propensity scores. During a median 7.9 (interquartile range: 3.5-12.0) person-years of follow-up, 2,596 incident cases of cancer were detected. Azathioprine use was associated with an increased risk of overall cancer (rate ratio = 1.41, 95% confidence interval: 1.15, 1.74), whereas former use of azathioprine (rate ratio = 1.02, 95% confidence interval: 0.83, 1.25) or increasing cumulative received doses (increase in rate ratio per 365 additional defined daily doses = 1.06, 95% confidence interval: 0.89, 1.27) were not. In subgroup analyses, azathioprine use was associated with increased risk of lymphoid tissue cancer (rate ratio = 2.40, 95% confidence interval: 1.13, 5.11) and urinary tract cancer (rate ratio = 2.84, 95% confidence interval: 1.24, 6.51). In conclusion, azathioprine use was associated with an increased risk of overall cancer in patients with inflammatory bowel disease, although these data cannot establish causality.

Cause-Specific Life Expectancies After 35 Years of Age for Human Immunodeficiency Syndrome-Infected and Human Immunodeficiency Syndrome-Negative Individuals Followed Simultaneously in Long-term Cohort Studies, 1984–2008

Abstract: Parametric and semiparametric competing risks methods were used to estimate proportions, timing, and predictors of acquired immune deficiency syndrome (AIDS)-related and non-AIDS-related mortality among individuals both positive and negative for the human immunodeficiency syndrome (HIV) in the Multicenter AIDS Cohort Study (MACS) and Women's Interagency HIV Study (WIHS) from 1984 to 2008 and 1996 to 2008, respectively. Among HIV-positive MACS participants, the proportion of deaths unrelated to AIDS increased from 6% before the introduction of highly active antiretroviral therapy (HAART) (before 1996) to 53% in the HAART era (P < 0.01); the median age of persons who died from non-AIDS-related causes after age 35 years increased from 49.0 to 66.0 years (P < 0.01). In both cohorts during the HAART era, median ages at time of non-AIDS-related death were younger for HIV-positive individuals than for comparable HIV-negative individuals (8.7 years younger in MACS (P < 0.01) and 7.6 years younger in WIHS (P < 0.01)). In a multivariate proportional cause-specific hazards model, unemployment (for non-AIDS death, hazard ratio (HR) = 1.8; for AIDS death, HR = 2.3), depression (for non-AIDS death, HR = 1.4; for AIDS death, HR = 1.4), and hepatitis B or C infection (for non-AIDS death, HR = 1.8, for AIDS death; HR = 1.4) were significantly (P < 0.05) associated with higher hazards of both non-AIDS and AIDS mortality among HIV-positive individuals in the HAART era, independent of study cohort. The results illuminate the changing face of mortality among the growing population infected with HIV.

Synergism Between Obesity and Alcohol in Increasing the Risk of Hepatocellular Carcinoma: A Prospective Cohort Study

Abstract: Obesity and alcohol interact to increase the risk of death from liver failure in men. In the present study, we aimed to examine whether obesity and alcohol were multiplicative or additive in increasing the risk of hepatocellular carcinoma (HCC) in both men and women. We conducted a prospective, population-based study of 23,712 Taiwanese residents (50.3% men) from 7 townships who underwent an evaluation for liver disease and were followed for 11.6 years for incident HCC. The mean age was 47 (standard deviation, 10) years and the mean body mass index (weight (kg)/height (m)(2)) was 24 (standard deviation, 3). Overall, 305 cases of HCC were identified over 275,126 person-years of follow-up. Age, male sex, alcohol drinking, cigarette smoking, elevated alanine aminotransferase, serum hepatitis B surface antigen, anti-hepatitis C virus positivity, and diabetes mellitus were each statistically significant predictors of incident HCC in univariate analyses (P < 0.05). Alcohol use and obesity (body mass index ≥30) showed a synergistic association with the risk of incident HCC in both unadjusted analyses (hazard ratio = 7.19, 95% confidence interval: 3.69, 14.00; P < 0.01) and multivariable-adjusted analyses (age, sex, smoking, serum alanine aminotransferase, serum hepatitis B surface antigen, anti-hepatitis C virus antibody, and diabetes mellitus) (hazard ratio = 3.82, 95% confidence interval: 1.94, 7.52; P < 0.01). Relative excess risks due to interaction, attributable proportion, and synergy index were 4.83, 0.67, and 4.53, respectively, suggesting a multiplicative interaction between alcohol use and obesity. Obesity and alcohol synergistically increase the risk of incident HCC.

Urinary Bisphenol A and Obesity in US Children

Abstract: Childhood obesity, a major public health problem, can lead to cardiovascular disease in adulthood. Studies have implicated exposure to bisphenol A (BPA), a commonly used chemical, in the development of obesity in adults. However, literature is limited on this association in children. We examined the association between urinary BPA and obesity in children aged 6-18 years from the National Health and Nutrition Examination Survey (2003-2008). The primary exposure was urinary BPA and the outcome was obesity, defined as the ≥ 95th percentile of body mass index specific for age and sex. We found a positive association between increasing levels of urinary BPA and obesity, independent of age, sex, race/ethnicity, education, physical activity, serum cotinine, and urinary creatinine. Compared with children in the lowest quartile of BPA ( 5.4 ng/mL) had a multivariable odds ratio for obesity of 2.55 (95% confidence interval (CI): 1.65, 3.95) (Ptrend < 0.01). The observed positive association was predominantly present in boys (odds ratio = 3.80, 95% CI: 2.25, 6.43) (Ptrend < 0.001) and in non-Hispanic whites (odds ratio = 5.87, 95% CI: 2.15, 16.05) (Ptrend < 0.01). In a representative sample of children, urinary BPA was associated with obesity, predominantly in non-Hispanic white boys, independent of major risk factors.

An Argument for a Consequentialist Epidemiology

Abstract: Epidemiology is the study of the causes and distributions of diseases in human populations so that we may identify ways to prevent and control disease. Although this definition broadly serves us well, I suggest that in recent decades, our discipline's robust interest in identifying causes has come at the expense of a more rigorous engagement with the second part of our vision for ourselves-the intent for us to intervene-and that this approach threatens to diminish our field's relevance. I argue here for a consequentialist epidemiology, a formalization and recalibration of the philosophical foundations of our discipline. I discuss how epidemiology is, at its core, more comfortably a consequentialist, as opposed to a deontological, discipline. A more consequentialist approach to epidemiology has several implications. It clarifies our research priorities, offers a perspective on the place of novel epidemiologic approaches and a metric to evaluate the utility of new methods, elevates the importance of global health and considerations about equity to the discipline, brings into sharp focus our engagement in implementation and translational science, and has implications for how we teach our students. I intend this article to be a provocation that can help clarify our disciplinary intentions.

Dairy-Food, Calcium, Magnesium, and Vitamin D Intake and Endometriosis: A Prospective Cohort Study

Abstract: The etiology of endometriosis is poorly understood, and few modifiable risk factors have been identified. Dairy foods and some nutrients can modulate inflammatory and immune factors, which are altered in women with endometriosis. We investigated whether intake of dairy foods, nutrients concentrated in dairy foods, and predicted plasma 25-hydroxyvitamin D (25(OH)D) levels were associated with incident laparoscopically confirmed endometriosis among 70,556 US women in Nurses’ Health Study II. Diet was assessed via food frequency questionnaire. A score for predicted 25(OH)D level was calculated for each participant. During 737,712 person-years of follow-up over a 14-year period (1991–2005), 1,385 cases of incident laparoscopically confirmed endometriosis were reported. Intakes of total and low-fat dairy foods were associated with a lower risk of endometriosis. Women consuming more than 3 servings of total dairy foods per day were 18% less likely to be diagnosed with endometriosis than those reporting 2 servings per day (rate ratio = 0.82, 95% confidence interval: 0.71, 0.95; Ptrend = 0.03). In addition, predicted plasma 25(OH)D level was inversely associated with endometriosis. Women in the highest quintile of predicted vitamin D level had a 24% lower risk of endometriosis than women in the lowest quintile (rate ratio = 0.76, 95% confidence interval: 0.60, 0.97; Ptrend = 0.004). Our findings suggest that greater predicted plasma 25(OH)D levels and higher intake of dairy foods are associated with a decreased risk of endometriosis.

Risk of Total and Aggressive Prostate Cancer and Pesticide Use in the Agricultural Health Study

Abstract: Because pesticides may operate through different mechanisms, the authors studied the risk of prostate cancer associated with specific pesticides in the Agricultural Health Study (1993-2007). With 1,962 incident cases, including 919 aggressive prostate cancers among 54,412 applicators, this is the largest study to date. Rate ratios and 95% confidence intervals were calculated by using Poisson regression to evaluate lifetime use of 48 pesticides and prostate cancer incidence. Three organophosphate insecticides were significantly associated with aggressive prostate cancer: fonofos (rate ratio (RR) for the highest quartile of exposure (Q4) vs. nonexposed = 1.63, 95% confidence interval (CI): 1.22, 2.17; P(trend) < 0.001); malathion (RR for Q4 vs. nonexposed = 1.43, 95% CI: 1.08, 1.88; P(trend) = 0.04); and terbufos (RR for Q4 vs. nonexposed = 1.29, 95% CI: 1.02, 1.64; P(trend) = 0.03). The organochlorine insecticide aldrin was also associated with increased risk of aggressive prostate cancer (RR for Q4 vs. nonexposed = 1.49, 95% CI: 1.03, 2.18; P(trend) = 0.02). This analysis has overcome several limitations of previous studies with the inclusion of a large number of cases with relevant exposure and detailed information on use of specific pesticides at 2 points in time. Furthermore, this is the first time specific pesticides are implicated as risk factors for aggressive prostate cancer.

Racial Disparities in Short Sleep Duration by Occupation and Industry

Abstract: Short sleep duration, which is associated with increased morbidity and mortality, has been shown to vary by occupation and industry, but few studies have investigated differences between black and white populations. By using data from a nationally representative sample of US adult short sleepers (n = 41,088) in the National Health Interview Survey in 2004–2011, we estimated prevalence ratios for short sleep duration in blacks compared with whites for each of 8 industry categories by using adjusted Poisson regression models with robust variance. Participants' mean age was 47 years; 50% were women and 13% were black. Blacks were more likely to report short sleep duration than whites (37% vs. 28%), and the black-white disparity was widest among those who held professional occupations. Adjusted short sleep duration was more prevalent in blacks than whites in the following industry categories: finance/information/real estate (prevalence ratio (PR) = 1.44, 95% confidence interval (CI): 1.30, 1.59); professional/administrative/management (PR = 1.30, 95% CI: 1.18, 1.44); educational services (PR = 1.39, 95% CI: 1.25, 1.54); public administration/arts/other services (PR = 1.30, 95% CI: 1.21, 1.41); health care/social assistance (PR = 1.23, 95% CI: 1.14, 1.32); and manufacturing/construction (PR = 1.14, 95% CI: 1.07, 1.20). Short sleep generally increased with increasing professional responsibility within a given industry among blacks but decreased with increasing professional roles among whites. Our results suggest the need for further investigation of racial/ethnic differences in the work-sleep relationship.

The Changing Epidemiology of Methicillin-Resistant Staphylococcus aureus in the United States: A National Observational Study

Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) can cause major illness and death and impose serious economic costs on patients and hospitals. Community-associated MRSA (CA-MRSA) is a growing problem in US hospitals, which are already dealing with high levels of hospital-associated MRSA (HA-MRSA), but little is known about how patient age and seasonal differences in the incidence of these 2 forms of MRSA affect the epidemic. By using national data on hospitalizations and antibiotic resistance, we estimated the magnitude and trends in annual S. aureus and MRSA hospitalization rates from 2005-2009 by patient age, infection type, and resistance phenotype (CA-MRSA vs. HA-MRSA). Although no statistically significant increase in the hospitalization rate was seen over the study period, the total number of infections increased. In 2009, there were an estimated 463,017 (95% confidence interval: 441,595, 484,439) MRSA-related hospitalizations at a rate of 11.74 (95% confidence interval: 11.20, 12.28) per 1,000 hospitalizations. We observed significant differences in infection type by age, with HA-MRSA-related hospitalizations being more common in older individuals. We also noted significant seasonality in incidence, particularly in children, with CA-MRSA peaking in the late summer and HA-MRSA peaking in the winter, which may be caused by seasonal shifts in antibiotic prescribing patterns.

Fruit and Vegetable Consumption and Mortality European Prospective Investigation Into Cancer and Nutrition

Abstract: In this study, the relation between fruit and vegetable consumption and mortality was investigated within the European Prospective Investigation Into Cancer and Nutrition. Survival analyses were performed, including 451,151 participants from 10 European countries, recruited between 1992 and 2000 and followed until 2010. Hazard ratios, rate advancement periods, and preventable proportions to respectively compare risk of death between quartiles of consumption, to estimate the period by which the risk of death was postponed among high consumers, and to estimate proportions of deaths that could be prevented if all participants would shift their consumption 1 quartile upward. Consumption of fruits and vegetables was inversely associated with all-cause mortality (for the highest quartile, hazard ratio = 0.90, 95% confidence interval (CI): 0.86, 0.94), with a rate advancement period of 1.12 years (95% CI: 0.70, 1.54), and with a preventable proportion of 2.95%. This association was driven mainly by cardiovascular disease mortality (for the highest quartile, hazard ratio = 0.85, 95% CI: 0.77, 0.93). Stronger inverse associations were observed for participants with high alcohol consumption or high body mass index and suggested in smokers. Inverse associations were stronger for raw than for cooked vegetable consumption. These results support the evidence that fruit and vegetable consumption is associated with a lower risk of death.

Mortality Risk Score Prediction in an Elderly Population Using Machine Learning

Abstract: Standard practice for prediction often relies on parametric regression methods. Interesting new methods from the machine learning literature have been introduced in epidemiologic studies, such as random forest and neural networks. However, a priori, an investigator will not know which algorithm to select and may wish to try several. Here I apply the super learner, an ensembling machine learning approach that combines multiple algorithms into a single algorithm and returns a prediction function with the best cross-validated mean squared error. Super learning is a generalization of stacking methods. I used super learning in the Study of Physical Performance and Age-Related Changes in Sonomans (SPPARCS) to predict death among 2,066 residents of Sonoma, California, aged 54 years or more during the period 1993-1999. The super learner for predicting death (risk score) improved upon all single algorithms in the collection of algorithms, although its performance was similar to that of several algorithms. Super learner outperformed the worst algorithm (neural networks) by 44% with respect to estimated cross-validated mean squared error and had an R2 value of 0.201. The improvement of super learner over random forest with respect to R2 was approximately 2-fold. Alternatives for risk score prediction include the super learner, which can provide improved performance.

Basal-Cell Carcinoma Incidence and Associated Risk Factors in US Women and Men

Abstract: There is a paucity of data on basal-cell carcinoma (BCC) in the United States, since most national registries do not collect information on BCC. We evaluated BCC incidence trends and associated risk factors for BCC in 140,171 participants from a U.S. female cohort, the Nurses' Health Study (1986-2006), and a U.S. male cohort, the Health Professionals' Follow-up Study (1988-2006). Age-adjusted BCC incidence rates increased from 519 cases per 100,000 person-years to 1,019 cases per 100,000 person years for women and increased from 606 cases per 100,000 person-years to 1,488 cases per 100,000 person-years for men during the follow-up period. Cox proportional hazards analysis identified the following phenotypic risk factors for BCC in both cohorts: family history of melanoma, blond or red hair colors, higher number of extremity moles, higher susceptibility to sunburn as a child/adolescent, and higher lifetime number of severe/blistering sunburns. The multivariate-adjusted risk ratio for the highest quintile of cumulative midrange ultraviolet B flux exposure versus the lowest quintile was 3.18 (95% confidence interval: 2.70, 3.76) in women and 1.90 (95% confidence interval: 1.57, 2.29) in men. BCC incidence was generally higher in men than in women, and BCC risk was strongly associated with several phenotypic and exposure factors, including midrange ultraviolet B radiation, in our study populations.

Associations Between Change in Sleep Duration and Inflammation: Findings on C-reactive Protein and Interleukin 6 in the Whitehall II Study

Abstract: Cross-sectional evidence suggests associations between sleep duration and levels of the inflammatory markers, C-reactive protein and interleukin-6. This longitudinal study uses data from the London-based Whitehall II study to examine whether changes in sleep duration are associated with average levels of inflammation from 2 measures 5 years apart. Sleep duration (≤5, 6, 7, 8, ≥9 hours on an average week night) was assessed in 5,003 middle-aged women and men in 1991/1994 and 1997/1999. Fasting levels of C-reactive protein and interleukin-6 were measured in 1997/1999 and 2002/2004. Cross-sectional analyses indicated that shorter sleep is associated with higher levels of inflammatory markers. Longitudinal analyses showed that each hour per night decrease in sleep duration between 1991/1994 and 1997/1999 was associated with higher levels of C-reactive protein (8.1%) and interleukin-6 (4.5%) averaged across measures in 1997/1999 and 2002/2004. Adjustment for longstanding illness and major cardiometabolic risk factors indicated that disease processes may partially underlie these associations. An increase in sleep duration was not associated with average levels of inflammatory markers. These results suggest that both short sleep and reductions in sleep are associated with average levels of inflammation over a 5-year period.

Firearms and Suicide in the United States: Is Risk Independent of Underlying Suicidal Behavior?

Abstract: On an average day in the United States, more than 100 Americans die by suicide; half of these suicides involve the use of firearms. In this ecological study, we used linear regression techniques and recently available state-level measures of suicide attempt rates to assess whether, and if so, to what extent, the well-established relationship between household firearm ownership rates and suicide mortality persists after accounting for rates of underlying suicidal behavior. After controlling for state-level suicide attempt rates (2008-2009), higher rates of firearm ownership (assessed in 2004) were strongly associated with higher rates of overall suicide and firearm suicide, but not with nonfirearm suicide (2008-2009). Furthermore, suicide attempt rates were not significantly related to gun ownership levels. These findings suggest that firearm ownership rates, independent of underlying rates of suicidal behavior, largely determine variations in suicide mortality across the 50 states. Our results support the hypothesis that firearms in the home impose suicide risk above and beyond the baseline risk and help explain why, year after year, several thousand more Americans die by suicide in states with higher than average household firearm ownership compared with states with lower than average firearm ownership. Language: en

Evaluating the Impact of Database Heterogeneity on Observational Study Results

Abstract: Clinical studies that use observational databases to evaluate the effects of medical products have become commonplace. Such studies begin by selecting a particular database, a decision that published papers invariably report but do not discuss. Studies of the same issue in different databases, however, can and do generate different results, sometimes with strikingly different clinical implications. In this paper, we systematically study heterogeneity among databases, holding other study methods constant, by exploring relative risk estimates for 53 drug-outcome pairs and 2 widely used study designs (cohort studies and self-controlled case series) across 10 observational databases. When holding the study design constant, our analysis shows that estimated relative risks range from a statistically significant decreased risk to a statistically significant increased risk in 11 of 53 (21%) of drug-outcome pairs that use a cohort design and 19 of 53 (36%) of drug-outcome pairs that use a self-controlled case series design. This exceeds the proportion of pairs that were consistent across databases in both direction and statistical significance, which was 9 of 53 (17%) for cohort studies and 5 of 53 (9%) for self-controlled case series. Our findings show that clinical studies that use observational databases can be sensitive to the choice of database. More attention is needed to consider how the choice of data source may be affecting results.

Obesity and Mortality Risk: New Findings From Body Mass Index Trajectories

Abstract: Little research has addressed the heterogeneity and mortality risk in body mass index (BMI) trajectories among older populations. Applying latent class trajectory models to 9,538 adults aged 51 to 77 years from the US Health and Retirement Study (1992-2008), we defined 6 latent BMI trajectories: normal weight downward, normal weight upward, overweight stable, overweight obesity, class I obese upward, and class II/III obese upward. Using survival analysis, we found that people in the overweight stable trajectory had the highest survival rate, followed by those in the overweight obesity, normal weight upward, class I obese upward, normal weight downward, and class II/III obese upward trajectories. The results were robust after controlling for baseline demographic and socioeconomic characteristics, smoking status, limitations in activities of daily living, a wide range of chronic illnesses, and self-rated health. Further analysis suggested that BMI trajectories were more predictive of mortality risk than was static BMI status. Using attributable risk analysis, we found that approximately 7.2% of deaths after 51 years of age among the 1931-1941 birth cohort were due to class I and class II/III obese upward trajectories. This suggests that trajectories of increasing obesity past 51 years of age pose a substantive threat to future gains in life expectancy.

Choline Intake During Pregnancy and Child Cognition at Age 7 Years

Abstract: Animal models indicate that exposure to choline in utero improves visual memory through cholinergic transmission and/or epigenetic mechanisms. Among 895 mothers in Project Viva (eastern Massachusetts, 1999-2002 to 2008-2011), we estimated the associations between intakes of choline, vitamin B12, betaine, and folate during the first and second trimesters of pregnancy and offspring visual memory (measured by the Wide Range Assessment of Memory and Learning, Second Edition (WRAML2), Design and Picture Memory subtests) and intelligence (measured using the Kaufman Brief Intelligence Test, Second Edition (KBIT-2)) at age 7 years. Mean second-trimester intakes were 328 (standard deviation (SD), 63) mg/day for choline, 10.5 (SD, 5.1) µg/day for vitamin B12, 240 (SD, 104) mg/day for betaine, and 1,268 (SD, 381) µg/day for folate. Mean age 7 test scores were 17.2 (SD, 4.4) points on the WRAML 2 Design and Picture Memory subtests, 114.3 (SD, 13.9) points on the verbal KBIT-2, and 107.8 (SD, 16.5) points on the nonverbal KBIT-2. In a model adjusting for maternal characteristics, the other nutrients, and child's age and sex, the top quartile of second-trimester choline intake was associated with a child WRAML2 score 1.4 points higher (95% confidence interval: 0.5, 2.4) than the bottom quartile (P-trend = 0.003). Results for first-trimester intake were in the same direction but weaker. Intake of the other nutrients was not associated with the cognitive tests administered. Higher gestational choline intake was associated with modestly better child visual memory at age 7 years.

Family Caregiving and All-Cause Mortality: Findings from a Population-based Propensity-matched Analysis

Abstract: Previous studies have provided conflicting evidence on whether being a family caregiver is associated with increased or decreased risk for all-cause mortality. This study examined whether 3,503 family caregivers enrolled in the national Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study showed differences in all-cause mortality from 2003 to 2012 compared with a propensity-matched sample of noncaregivers. Caregivers were individually matched with 3,503 noncaregivers by using a propensity score matching procedure based on 15 demographic, health history, and health behavior covariates. During an average 6-year follow-up period, 264 (7.5%) of the caregivers died, which was significantly fewer than the 315 (9.0%) matched noncaregivers who died during the same period. A proportional hazards model indicated that caregivers had an 18% reduced rate of death compared with noncaregivers (hazard ratio = 0.823, 95% confidence interval: 0.699, 0.969). Subgroup analyses by race, sex, caregiving relationship, and caregiving strain failed to identify any subgroups with increased rates of death compared with matched noncaregivers. Public policy and discourse should recognize that providing care to a family member with a chronic illness or disability is not associated with increased risk of death in most cases, but may instead be associated with modest survival benefits for the caregivers.

Risk of Pelvic Inflammatory Disease Following Chlamydia trachomatis Infection: Analysis of Prospective Studies With a Multistate Model

Abstract: Our objective in this study was to estimate the probability that a Chlamydia trachomatis (CT) infection will cause an episode of clinical pelvic inflammatory disease (PID) and the reduction in such episodes among women with CT that could be achieved by annual screening. We reappraised evidence from randomized controlled trials of screening and controlled observational studies that followed untreated CT-infected and -uninfected women to measure the development of PID. Data from these studies were synthesized using a continuous-time Markov model which takes into account the competing risk of spontaneous clearance of CT. Using a 2-step piecewise homogenous Markov model that accounts for the distinction between prevalent and incident infections, we investigated the possibility that the rate of PID due to CT is greater during the period immediately following infection. The available data were compatible with both the homogenous and piecewise homogenous models. Given a homogenous model, the probability that a CT episode will cause clinical PID was 0.16 (95% credible interval (CrI): 0.06, 0.25), and annual screening would prevent 61% (95% CrI: 55, 67) of CT-related PID in women who became infected with CT. Assuming a piecewise homogenous model with a higher rate during the first 60 days, corresponding results were 0.16 (95% CrI: 0.07, 0.26) and 55% (95% CrI: 32, 72), respectively.