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5.  Invited Commentary: The Etiology of Lung Cancer in Men Compared With Women 
American Journal of Epidemiology  2013;177(7):613-616.
Lung cancer is the leading cause of cancer death among women in the United States and other Western nations. The predominant cause of lung cancer in women is active cigarette smoking. Secondhand exposure to tobacco smoke is another important cause. The hypothesis that women are more susceptible than men to smoking-induced lung cancer has not been supported by the preponderance of current data, as noted by De Matteis et al. (Am J Epidemiol. 2013;177(7):601–612) in the accompanying article. However, aspects of lung cancer in men and women continue to indicate potential male-female differences in the etiology of lung cancer, based on several observations: 1) among never smokers, women have higher lung cancer incidence rates than men; 2) there is evidence that estrogen may contribute to lung cancer risk and progression; and 3) there are different clinical characteristics of lung cancer in women compared with men, such as the higher percentage of adenocarcinomas in never smokers, the greater prevalence of epidermal growth factor receptor gene (EGFR) mutations in adenocarcinomas among never smokers, and better prognosis. Considered in total, observations such as these offer enticing clues that, even amid cigarette smoking and other commonalities in the etiology of lung cancer in men and women, distinct differences may remain to be delineated that could potentially be of scientific and clinical relevance.
doi:10.1093/aje/kws444
PMCID: PMC3657534  PMID: 23425628
cigarettes; estrogen; lung cancer; men; secondhand smoke exposure; sex; smoking; women
6.  Differences in Epidemiologic Risk Factors for Colorectal Adenomas and Serrated Polyps by Lesion Severity and Anatomical Site 
American Journal of Epidemiology  2013;177(7):625-637.
Using a case-control design, we evaluated differences in risk factors for colorectal polyps according to histological type, anatomical site, and severity. Participants were enrollees in the Group Health Cooperative aged 20–79 years who underwent colonoscopy in Seattle, Washington, between 1998 and 2007 and comprised 628 adenoma cases, 594 serrated polyp cases, 247 cases with both types of polyps, and 1,037 polyp-free controls. Participants completed a structured interview, and polyps were evaluated via standardized pathology review. We used multivariable polytomous logistic regression to compare case groups with controls and with the other case groups. Factors for which the strength of the association varied significantly between adenomas and serrated polyps were sex (P < 0.001), use of estrogen-only postmenopausal hormone therapy (P = 0.01), and smoking status (P < 0.001). For lesion severity, prior endoscopy (P < 0.001) and age (P = 0.05) had significantly stronger associations with advanced adenomas than with nonadvanced adenomas; and higher education was positively correlated with sessile serrated polyps but not with other serrated polyps (P = 0.02). Statistically significant, site-specific associations were observed for current cigarette smoking (P = 0.05 among adenomas and P < 0.001 among serrated polyps), postmenopausal estrogen-only therapy (P = 0.01 among adenomas), and obesity (P = 0.01 among serrated polyps). These findings further illustrate the epidemiologic heterogeneity of colorectal neoplasia and may help elucidate carcinogenic mechanisms for distinct pathways.
doi:10.1093/aje/kws282
PMCID: PMC3657530  PMID: 23459948
adenoma; colorectal polyps; risk factors; serrated polyps
7.  Validation of Different Instruments for Caffeine Measurement Among Premenopausal Women in the BioCycle Study 
American Journal of Epidemiology  2013;177(7):690-699.
Effects of caffeine on women's health are inconclusive, in part because of inadequate exposure assessment. In this study we determined 1) validity of a food frequency questionnaire compared with multiple 24-hour dietary recalls (24HDRs) for measuring monthly caffeine and caffeinated beverage intakes; and 2) validity of the 24HDR compared with the prior day's diary record for measuring daily caffeinated coffee intake. BioCycle Study (2005–2007) participants, women (n = 259) aged 18–44 years from western New York State, were followed for 2 menstrual cycles. Participants completed a food frequency questionnaire at the end of each cycle, four 24HDRs per cycle, and daily diaries. Caffeine intakes reported for the food frequency questionnaires were greater than those reported for the 24HDRs (mean = 114.1 vs. 92.6mg/day, P = 0.01) but showed high correlation (r = 0.73, P < 0.001) and moderate agreement (К = 0.51, 95% confidence interval: 0.43, 0.57). Women reported less caffeinated coffee intake in their 24HDRs compared with their corresponding diary days (mean = 0.51 vs. 0.80 cups/day, P < 0.001) (1 cup = 237 mL). Although caffeine and coffee exposures were highly correlated, absolute intakes differed significantly between measurement tools. These results highlight the importance of considering potential misclassification of caffeine exposure.
doi:10.1093/aje/kws283
PMCID: PMC3657531  PMID: 23462965
beverages; caffeine; diet; mental recall; nutrition assessment; questionnaires; validation studies; women
8.  Characterizing Durations of Heroin Abstinence in the California Civil Addict Program: Results From a 33-Year Observational Cohort Study 
American Journal of Epidemiology  2013;177(7):675-682.
In accordance with the chronic disease model of opioid dependence, cessation is often observed as a longitudinal process rather than a discrete endpoint. We aimed to characterize and identify predictors of periods of heroin abstinence in the natural history of recovery from opioid dependence. Data were collected on participants from California who were enrolled in the Civil Addict Program from 1962 onward by use of a natural history interview. Multivariate regression using proportional hazards frailty models was applied to identify independent predictors and correlates of repeated abstinence episode durations. Among 471 heroin-dependent males, 387 (82.2%) reported 932 abstinence episodes, 60.3% of which lasted at least 1 year. Multivariate analysis revealed several important findings. First, demographic factors such as age and ethnicity did not explain variation in durations of abstinence episodes. However, employment and lower drug use severity predicted longer episodes. Second, abstinence durations were longer following sustained treatment versus incarceration. Third, individuals with multiple abstinence episodes remained abstinent for longer durations in successive episodes. Finally, abstinence episodes initiated >10 and ≤20 years after first use lasted longer than others. Public policy facilitating engagement of opioid-dependent individuals in maintenance-oriented drug treatment and employment is recommended to achieve and sustain opioid abstinence.
doi:10.1093/aje/kws284
PMCID: PMC3657532  PMID: 23445901
abstinence; Cox proportional hazards; frailty models; γ-frailty models; heroin use; illicit drug use; opioid dependence; substance abuse treatment
9.  Association of Leukocyte Telomere Length With Breast Cancer Risk: Nested Case-Control Findings From the Shanghai Women's Health Study 
American Journal of Epidemiology  2013;177(7):617-624.
Telomeres are specialized chromatin structures essential for the maintenance of chromosomal integrity and stability. Telomere shortening has been linked to multiple aging-related diseases, including cancer. Evidence associating telomere length with breast cancer risk—most of which has been from retrospective case-control studies—is conflicting. We conducted a nested case-control study based on the Shanghai Women's Health Study (1997–2009) in which we evaluated the association of telomere length and breast cancer risk using peripheral blood samples collected before cancer diagnosis (601 cases and 695 controls). We used monochrome multiplex quantitative polymerase chain reaction to measure relative telomere length. Multiple logistic regressions were used to derive adjusted odds ratios with 95% confidence intervals as the measure of association. Telomere length was inversely correlated with age (r = −0.22). Women with moderately long telomeres (those in the fourth quintile) had the lowest breast cancer risk. Risk increased in a dose-response manner with decreasing quintile of telomere length; odds ratios were 1.39 (95% confidence interval (CI): 0.95, 2.04), 1.79 (95% CI: 1.17, 2.75), and 2.39 (95% CI: 1.45, 3.92), respectively, for the third, second, and first quintiles compared with the fourth quintile. A slightly elevated risk of breast cancer (odds ratio = 1.35, 95% CI: 0.90, 2.04), although one that was not statistically significant, was found in the top quintile (longest telomeres). Our results support the hypothesis that telomere shortening is associated with increased risk of breast cancer and suggest a possible elevated risk associated with long telomeres.
doi:10.1093/aje/kws291
PMCID: PMC3657533  PMID: 23444102
breast cancer; biomarkers; epidemiology; genetic factors; telomere
10.  Are Women Who Smoke at Higher Risk for Lung Cancer Than Men Who Smoke? 
American Journal of Epidemiology  2013;177(7):601-612.
Worldwide lung cancer incidence is decreasing or leveling off among men, but rising among women. Sex differences in associations of tobacco carcinogens with lung cancer risk have been hypothesized, but the epidemiologic evidence is conflicting. We tested sex-smoking interaction in association with lung cancer risk within a population-based case-control study, the Environment and Genetics in Lung Cancer Etiology (EAGLE) Study (Lombardy, Italy, 2002–2005). Detailed lifetime smoking histories were collected by personal interview in 2,100 cases with incident lung cancer and 2,120 controls. Odds ratios and 95% confidence intervals for pack-years of cigarette smoking were estimated by logistic regression, adjusted for age, residence area, and time since quitting smoking. To assess sex-smoking interaction, we compared the slopes of odds ratios for logarithm of pack-years in a model for men and women combined. Overall, the slope for pack-years was steeper in men (odds ratio for female-smoking interaction = 0.39, 95% confidence interval: 0.24, 0.62; P < 0.0001); after restriction to ever smokers, the difference in slopes was much smaller (odds ratio for interaction = 0.63, 95% confidence interval: 0.29, 1.37; P = 0.24). Similar results were found by histological type. Results were unchanged when additional confounders were evaluated (e.g., tobacco type, inhalation depth, Fagerström-assessed nicotine dependence). These findings do not support a higher female susceptibility to tobacco-related lung cancer.
doi:10.1093/aje/kws445
PMCID: PMC3657535  PMID: 23425629
case-control studies; lung cancer; sex differences; smoking
11.  “If It Isn't Ultimately Aimed at Policy, It's Not Worth Doing” 
American Journal of Epidemiology  2013;177(7):595-600.
George W. Comstock (1915–2007), MD, MPH, DrPH, was lecturer and then professor of epidemiology at the Johns Hopkins University School of Hygiene and Public Health from 1956 to 2007 and served as editor-in-chief of the American Journal of Epidemiology from 1979 to 1988. This interview of George W. Comstock took place in Hagerstown, Maryland, in the spring of 1990. The selection of questions and answers published here represent approximately 10% of the whole interview, which had been reviewed and hand-corrected by Dr. Comstock. He first describes how epidemiology was taught at Hopkins in the 1950s and 1960s. He then distinguishes “epidemiology per se” from a “practical epidemiology” that works closely with local health departments, and he finally expresses his wish that in the future, epidemiology would become more widely involved in policy and accepted by policy makers. Photo of George, Margaret, and Gordon Comstock taken during World War II, most likely in 1944, while Dr Comstock was serving as Medical Officer in an Escort Destroyer Division.
doi:10.1093/aje/kwt027
PMCID: PMC3657536  PMID: 23545720
history; interview; policy; teaching
12.  A Class of Transformation Covariate Regression Models for Estimating the Excess Hazard in Relative Survival Analysis 
American Journal of Epidemiology  2013;177(7):708-717.
Relative survival is the standard measure of excess mortality due to cancer in population-based cancer survival studies. In relative survival analysis, the observed hazard for cancer patients is the sum of the expected hazard for the general cancer-free population and the excess hazard associated with a cancer diagnosis. Previous models for relative survival analysis have assumed that the excess hazard rate is related to covariates by additive or multiplicative regression models. In this paper, a transformation covariate regression model is developed for estimation of the excess hazard rate, which includes both the additive and the multiplicative regression models as special cases. The baseline excess hazard rate and time-dependent hazard ratios can be approximated by means of regression splines, and the parameter estimates can be obtained using a standard statistical package. As is demonstrated through simulation, the proposed transformation hazards model provides a reasonably good fit to typical relative survival data. For illustration purposes, the sex difference in relative survival for lung and bronchus cancer patients is examined using data from population-based cancer registries (1973–2003).
doi:10.1093/aje/kws288
PMCID: PMC3665316  PMID: 23492766
additive hazards; multiplicative hazards; relative survival; transformation hazards
13.  Physical Activity Assessment: Biomarkers and Self-Report of Activity-Related Energy Expenditure in the WHI 
American Journal of Epidemiology  2013;177(6):576-585.
We used a biomarker of activity-related energy expenditure (AREE) to assess measurement properties of self-reported physical activity and to determine the usefulness of AREE regression calibration equations in the Women's Health Initiative. Biomarker AREE, calculated as the total energy expenditure from doubly labeled water minus the resting energy expenditure from indirect calorimetry, was assessed in 450 Women's Health Initiative participants (2007–2009). Self-reported AREE was obtained from the Arizona Activity Frequency Questionnaire (AAFQ), the 7-Day Physical Activity Recall (PAR), and the Women's Health Initiative Personal Habits Questionnaire (PHQ). Eighty-eight participants repeated the protocol 6 months later. Reporting error, measured as log(self-report AREE) minus log(biomarker AREE), was regressed on participant characteristics for each instrument. Body mass index was associated with underreporting on the AAFQ and PHQ but overreporting on PAR. Blacks and Hispanics underreported physical activity levels on the AAFQ and PAR, respectively. Underreporting decreased with age for the PAR and PHQ. Regressing logbiomarker AREE on logself-reported AREE revealed that self-report alone explained minimal biomarker variance (R2 = 7.6, 4.8, and 3.4 for AAFQ, PAR, and PHQ, respectively). R2 increased to 25.2, 21.5, and 21.8, respectively, when participant characteristics were included. Six-month repeatability data adjusted for temporal biomarker variation, improving R2 to 79.4, 67.8, and 68.7 for AAFQ, PAR, and PHQ, respectively. Calibration equations “recover” substantial variation in average AREE and valuably enhance AREE self-assessment.
doi:10.1093/aje/kws269
PMCID: PMC3626043  PMID: 23436896
biomakers; measurement error; physical activity; postmenopausal women
14.  Modeling the Role of Public Transportation in Sustaining Tuberculosis Transmission in South Africa 
American Journal of Epidemiology  2013;177(6):556-561.
Current tuberculosis notification rates in South Africa are among the highest ever recorded. Although the human immunodeficiency virus epidemic has been a critical factor, the density of respiratory contacts in high-risk environments may be an important and underappreciated driver. Using a modified Wells-Riley model for airborne disease transmission, we estimated the risk of tuberculosis transmission on 3 modes of public transit (minibus taxis, buses, and trains) in Cape Town, South Africa, using exhaled carbon dioxide as a natural tracer gas to evaluate air exchange. Carbon dioxide measurements were performed between October and December of 2011. Environmental risk, reflected in the rebreathed fraction of air, was highest in minibus taxis and lowest in trains; however, the average number of passengers sharing an indoor space was highest in trains and lowest in minibus taxis. Among daily commuters, the annual risk of tuberculosis infection was projected to be 3.5%–5.0% and was highest among minibus taxi commuters. Assuming a duration of infectiousness of 1 year, the basic reproductive number attributable to transportation was more than 1 in all 3 modes of transportation. Given its poor ventilation and high respiratory contact rates, public transportation may play a critical role in sustaining tuberculosis transmission in South African cities.
doi:10.1093/aje/kws331
PMCID: PMC3657527  PMID: 23423215
HIV; indoor air quality; mathematical model; transmission; tuberculosis
15.  Invited Commentary: Reproductive Organ Surgeries and Breast Cancer Risk—Apples, Oranges, or Fruit Cocktail? 
American Journal of Epidemiology  2013;177(6):500-503.
Case-control and cohort studies are almost always complicated by nonrandom exposure allocation, which must be minimized in the design and analysis phases. Tubal sterilization is a common gynecological procedure that may be associated with other reproductive organ surgeries, which in turn may be associated with breast cancer risk. In this issue of the Journal, Gaudet et al. (Am J Epidemiol. 2013;177(6):492–499) argue successfully that tubal sterilization is unassociated with breast cancer risk. Scrutiny of the heterogeneous studies included in their meta-analysis underscores the role of confounding and effect modification in observational epidemiologic studies. Specifically, tubal sterilization is unassociated with breast cancer risk, but either oophorectomy or hysterectomy, or both, and the timing of these procedures warrant careful consideration in the design, analysis, and interpretation of observational research on reproductive factors.
doi:10.1093/aje/kws438
PMCID: PMC3657528  PMID: 23416446
breast neoplasms; case-control studies; cohort studies; hysterectomy; meta-analysis; oophorectomy; tubal sterilization
16.  Index-based Dietary Patterns and the Risk of Prostate Cancer in the NIH-AARP Diet and Health Study 
American Journal of Epidemiology  2013;177(6):504-513.
Few studies have investigated the relationship between overall diet and the risk of prostate cancer. We examined the association between 3 diet quality indices—the Healthy Eating Index-2005 (HEI-2005), Alternate Healthy Eating Index-2010 (AHEI-2010), and alternate Mediterranean diet score (aMED)—and prostate cancer risk. At baseline, dietary intake was assessed in a cohort of 293,464 US men in the National Institutes of Health (NIH)-AARP Diet and Health Study. Cox proportional hazards regression was used to estimate hazard ratios. Between 1995 and 2006, we ascertained 23,453 incident cases of prostate cancer, including 2,251 advanced cases and 428 fatal cases. Among men who reported a history of prostate-specific antigen testing, high HEI-2005 and AHEI-2010 scores were associated with lower risk of total prostate cancer (for the highest quintile compared with the lowest, hazard ratio (HR) = 0.92, 95% confidence interval (CI): 0.86, 0.98, P for trend = 0.01; and HR = 0.93, 95% CI: 0.88, 0.99, P for trend = 0.05, respectively). No significant association was observed between aMED score and total prostate cancer or between any of the indices and advanced or fatal prostate cancer, regardless of prostate-specific antigen testing status. In individual component analyses, the fish component of aMED and ω-3 fatty acids component of AHEI-2010 were inversely associated with fatal prostate cancer (HR = 0.79, 95% CI: 0.65, 0.96, and HR = 0.94, 95% CI: 0.90, 0.98, respectively).
doi:10.1093/aje/kws261
PMCID: PMC3657529  PMID: 23408548
diet; food habits; prostatic neoplasms
17.  Missing Doses in the Life Span Study of Japanese Atomic Bomb Survivors 
American Journal of Epidemiology  2013;177(6):562-568.
The Life Span Study of atomic bomb survivors is an important source of risk estimates used to inform radiation protection and compensation. Interviews with survivors in the 1950s and 1960s provided information needed to estimate radiation doses for survivors proximal to ground zero. Because of a lack of interview or the complexity of shielding, doses are missing for 7,058 of the 68,119 proximal survivors. Recent analyses excluded people with missing doses, and despite the protracted collection of interview information necessary to estimate some survivors' doses, defined start of follow-up as October 1, 1950, for everyone. We describe the prevalence of missing doses and its association with mortality, distance from hypocenter, city, age, and sex. Missing doses were more common among Nagasaki residents than among Hiroshima residents (prevalence ratio = 2.05; 95% confidence interval: 1.96, 2.14), among people who were closer to ground zero than among those who were far from it, among people who were younger at enrollment than among those who were older, and among males than among females (prevalence ratio = 1.22; 95% confidence interval: 1.17, 1.28). Missing dose was associated with all-cancer and leukemia mortality, particularly during the first years of follow-up (all-cancer rate ratio = 2.16, 95% confidence interval: 1.51, 3.08; and leukemia rate ratio = 4.28, 95% confidence interval: 1.72, 10.67). Accounting for missing dose and late entry should reduce bias in estimated dose-mortality associations.
doi:10.1093/aje/kws362
PMCID: PMC3592497  PMID: 23429722
atomic bombs; cohort studies; ionizing radiation; missing data; mortality; nuclear weapons
18.  Preclinical Serum 25-Hydroxyvitamin D Levels and Risk of Type 1 Diabetes in a Cohort of US Military Personnel 
American Journal of Epidemiology  2013;177(5):411-419.
To determine whether serum levels of 25-hydroxyvitamin D (25(OH)D) in young adults are associated with risk of type 1 diabetes mellitus (T1D), we conducted a prospective, nested case-control study among US active-duty military personnel with serum in the US Department of Defense Serum Repository, identifying 310 T1D cases diagnosed between 1997 and 2009 with at least 2 serum samples collected before disease onset and 613 controls matched to cases on age, sex, race/ethnicity, branch of military service, and dates of serum collection. Conditional logistic regression was used to estimate rate ratios and 95% confidence intervals. Among non-Hispanic whites, those with average 25(OH)D levels of ≥100 nmol/L had a 44% lower risk of developing T1D than those with average 25(OH)D levels <75 nmol/L (rate ratio = 0.56, 95% confidence interval: 0.35, 0.90, P for trend = 0.03) over an average follow-up of 5.4 years. In quintile analyses, T1D risk was highest among individuals whose 25(OH)D levels were in the lowest 20% of those measured. There was no association between 25(OH)D levels and risk of T1D among non-Hispanic blacks or Hispanics. Low 25(OH)D levels may predispose healthy, young, non-Hispanic white adults to the development of T1D.
doi:10.1093/aje/kws243
PMCID: PMC3626044  PMID: 23380046
nested case-control study; type 1 diabetes; vitamin D
19.  Racial Disparities in Survival Among Injured Drivers 
American Journal of Epidemiology  2013;177(5):380-387.
Prior studies on racial and ethnic disparities in survival after motor vehicle crashes have examined only population-based death rates or have been restricted to hospitalized patients. In the current study, we examined 3 components of crash survival by race/ethnicity: survival overall, survival to reach a hospital, and survival among those hospitalized. Nine years of data (from 2000 through 2008) from the National Automotive Sampling System Crashworthiness Data System were used to examine white non-Hispanic, black non-Hispanic, and Hispanic drivers aged ≥15 years with serious injuries (injury severity scores of ≥9). By using multivariable logistic regression, we found that a driver's race/ethnicity was not significantly associated with overall survival after being injured in a crash (for blacks, odds ratio (OR) = 0.69, 95% confidence interval (CI): 0.36, 1.32; for Hispanics, OR = 1.00, 95% CI: 0.59, 1.72), and blacks and Hispanics were equally likely to survive to be treated at a hospital compared with whites (for blacks, OR = 1.00, 95% CI: 0.52, 1.93; for Hispanics, OR = 1.13, 95% CI: 0.71, 1.79). However, among patients who were treated at a hospital, blacks were 50% less likely to survive 30 days compared with whites (OR = 0.50, 95% CI: 0.33, 0.76). The disparity in survival after serious traffic injuries among blacks appears to occur after hospitalization, not in prehospital survival.
doi:10.1093/aje/kws242
PMCID: PMC3626045  PMID: 23371352
accidents; continental population groups; hospitalization; traffic; wounds and injuries
20.  Racial Differences in the Association Between Night Shift Work and Melatonin Levels Among Women 
American Journal of Epidemiology  2013;177(5):388-393.
Reduced suppression of melatonin in response to working the night shift among people of Asian ancestry has been suggested as a possible explanation for the null results observed in a recent analysis of shift work and breast cancer risk in a Chinese cohort. The authors analyzed the impact of Asian versus white race on previously reported differences in urinary 6-sulfatoxymelatonin levels in a 2003–2008 study in Seattle, Washington, of female health-care workers that exclusively worked night or day shifts. A total of 225 white and 51 Asian participants were included in the analysis. Although 6-sulfatoxymelatonin levels were affected by night shift work in both racial groups, Asian night shift workers consistently showed 6-sulfatoxymelatonin levels that were closer to levels in day shift workers than did white night shift workers. Furthermore, differences in 6-sulfatoxymelatonin levels between white and Asian night shift workers relative to day shift workers were statistically significant in every instance (P < 0.05). These results suggest that Asians may be better able to maintain a “normal” circadian pattern of melatonin production compared with whites and suggest a biological mechanism by which Asian night shift workers may be at a reduced risk of cancer.
doi:10.1093/aje/kws278
PMCID: PMC3626046  PMID: 23380044
cancer; melatonin; race; shift work
21.  The Sleep-Time Cost of Parenting: Sleep Duration and Sleepiness Among Employed Parents in the Wisconsin Sleep Cohort Study 
American Journal of Epidemiology  2013;177(5):394-401.
Insufficient sleep is associated with poor health and increased mortality. Studies on whether parenthood (including consideration of number and ages of children) is associated with sleep duration or sleep problems are scant and inconclusive. Using data collected in the Wisconsin Sleep Cohort Study (n = 4,809) between 1989 and 2008, we examined cross-sectional associations of number and ages of children with self-reported parental sleep duration, daytime sleepiness, and dozing among employed adults. Longitudinal change in sleep duration over 19 years was examined to evaluate changes in parental sleep associated with children transitioning into adulthood (n = 833). Each child under age 2 years was associated with 13 fewer minutes of parental sleep per day (95% confidence interval (CI): 5, 21); each child aged 2–5 years was associated with 9 fewer minutes of sleep (95% CI: 5, 13); and each child aged 6–18 years was associated with 4 fewer minutes (95% CI: 2, 6). Adult children were not associated with shorter parental sleep duration. Parents of children over age 2 years were significantly more likely to experience daytime sleepiness and dozing during daytime activities. Parents of minor children at baseline had significantly greater increases in sleep duration over 19 years of follow-up. Parenting minor children is associated with shorter sleep duration. As children age into adulthood, the sleep duration of parents with more children approaches that of parents with fewer children.
doi:10.1093/aje/kws246
PMCID: PMC3626047  PMID: 23378502
adult; cohort studies; humans, middle aged; parents; sleep; sleep duration
22.  Dairy-Food, Calcium, Magnesium, and Vitamin D Intake and Endometriosis: A Prospective Cohort Study 
American Journal of Epidemiology  2013;177(5):420-430.
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.
doi:10.1093/aje/kws247
PMCID: PMC3626048  PMID: 23380045
dairy foods; diet; endometriosis; magnesium; phosphorus; vitamin D
23.  The Association of Early Life Supplemental Nutrition With Lean Body Mass and Grip Strength in Adulthood: Evidence From APCAPS 
American Journal of Epidemiology  2014;179(6):700-709.
In the present study, we examined the associations of early nutrition with adult lean body mass (LBM) and muscle strength in a birth cohort that was established to assess the long-term impact of a nutrition program. Participants (n = 1,446, 32% female) were born near Hyderabad, India, in 29 villages from 1987 to 1990, during which time only intervention villages (n = 15) had a government program that offered balanced protein-calorie supplementation to pregnant women and children. Participants’ LBM and appendicular skeletal muscle mass were measured using dual energy x-ray absorptiometry; grip strength and information on lifestyle indicators, including diet and physical activity level, were also obtained. Ages (mean = 20.3 years) and body mass indexes (weight (kg)/height (m)2; mean = 19.5) of participants in 2 groups were similar. Current dietary energy intake was higher in the intervention group. Unadjusted LBM and grip strength were similar in 2 groups. After adjustment for potential confounders, the intervention group had lower LBM (β = −0.75; P = 0.03), appendicular skeletal muscle mass, and grip strength than did controls, but these differences were small in magnitude (<0.1 standard deviation). Multivariable regression analyses showed that current socioeconomic position, energy intake, and physical activity level had a positive association with adult LBM and muscle strength. This study could not detect a “programming” effect of early nutrition supplementation on adult LBM and muscle strength.
doi:10.1093/aje/kwt332
PMCID: PMC3939852  PMID: 24553777
body composition; cohort study; developmental origins of health and disease; grip strength; lean body mass; muscle mass; nutrition; physical activity
24.  Invited Commentary: Integrating a Life-Course Perspective and Social Theory to Advance Research on Residential Segregation and Health 
American Journal of Epidemiology  2013;177(4):310-315.
Research on racial residential segregation and health typically uses multilevel, population-based, slice-in-time data. Although research using this approach, including that by Kershaw et al. (Am J Epidemiol. 2013;177(4):299–309), has been valuable, I argue that to advance our understanding of how residential segregation influences health and health disparities, it is critical to incorporate a life-course perspective and integrate social theory. Applying a life-course perspective would entail modeling transitions, cumulative risk, and developmental and dynamic processes and mechanisms, as well as recognizing the contingency of contextual effects on different social groups. I discuss the need for analytic methods appropriate for modeling health effects of distal causes experienced across the life course, such as segregation, that operate through multiple levels and sequences of mediators, potentially across decades. Sociological theories of neighborhood attainment (e.g., segmented assimilation, ethnic resurgence, and place stratification theories) can guide effect-modification tests to help illuminate health effects resulting from intersections of residential processes, race/ethnicity, immigration, and other social determinants of health. For example, nativity and immigration history may crucially shape residential processes and exposures, but these have received limited attention in prior segregation-health literature.
doi:10.1093/aje/kws371
PMCID: PMC3566708  PMID: 23337313
neighborhood effects; place; racial residential segregation; social epidemiology; social theory
25.  Racial and Ethnic Residential Segregation, the Neighborhood Socioeconomic Environment, and Obesity Among Blacks and Mexican Americans 
American Journal of Epidemiology  2013;177(4):299-309.
We used cross-sectional data on 2,660 black and 2,611 Mexican-American adult participants in the National Health and Nutrition Examination Survey (1999–2006) to investigate the association between metropolitan-level racial/ethnic residential segregation and obesity and to determine whether it was mediated by the neighborhood socioeconomic environment. Residential segregation was measured using the black and Hispanic isolation indices. Neighborhood poverty and negative income incongruity were assessed as mediators. Multilevel Poisson regression with robust variance estimates was used to estimate prevalence ratios. There was no relationship between segregation and obesity among men. Among black women, in age-, nativity-, and metropolitan demographic-adjusted models, high segregation was associated with a 1.29 (95% confidence interval (CI): 1.00, 1.65) times higher obesity prevalence than was low segregation; medium segregation was associated with a 1.35 (95% CI: 1.07, 1.70) times higher obesity prevalence. Mexican-American women living in high versus low segregation areas had a significantly lower obesity prevalence (prevalence ratio, 0.54; 95% CI: 0.33, 0.90), but there was no difference between those living in medium versus low segregation areas. These associations were not mediated by neighborhood poverty or negative income incongruity. These findings suggest variability in the interrelationships between residential segregation and obesity for black and Mexican-American women.
doi:10.1093/aje/kws372
PMCID: PMC3566709  PMID: 23337312
health disparities; obesity; residential segregation; social environment

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