Thomas W. McDade

Neighborhoods, Obesity, and Diabetes — A Randomized Social Experiment

BACKGROUND The question of whether neighborhood environment contributes directly to the development of obesity and diabetes remains unresolved. The study reported on here uses data from a social experiment to assess the association of randomly assigned variation in neighborhood conditions with obesity and diabetes. METHODS From 1994 through 1998, the Department of Housing and Urban Development (HUD) randomly assigned 4498 women with children living in public housing in high-poverty urban census tracts (in which ≥40% of residents had incomes below the federal poverty threshold) to one of three groups: 1788 were assigned to receive housing vouchers, which were redeemable only if they moved to a low-poverty census tract (where <10% of residents were poor), and counseling on moving; 1312 were assigned to receive unrestricted, traditional vouchers, with no special counseling on moving; and 1398 were assigned to a control group that was offered neither of these opportunities. From 2008 through 2010, as part of a long-term follow-up survey, we measured data indicating health outcomes, including height, weight, and level of glycated hemoglobin (HbA(1c)). RESULTS As part of our long-term survey, we obtained data on body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) for 84.2% of participants and data on glycated hemoglobin level for 71.3% of participants. Response rates were similar across randomized groups. The prevalences of a BMI of 35 or more, a BMI of 40 or more, and a glycated hemoglobin level of 6.5% or more were lower in the group receiving the low-poverty vouchers than in the control group, with an absolute difference of 4.61 percentage points (95% confidence interval [CI], -8.54 to -0.69), 3.38 percentage points (95% CI, -6.39 to -0.36), and 4.31 percentage points (95% CI, -7.82 to -0.80), respectively. The differences between the group receiving traditional vouchers and the control group were not significant. CONCLUSIONS The opportunity to move from a neighborhood with a high level of poverty to one with a lower level of poverty was associated with modest but potentially important reductions in the prevalence of extreme obesity and diabetes. The mechanisms underlying these associations remain unclear but warrant further investigation, given their potential to guide the design of community-level interventions intended to improve health. (Funded by HUD and others.).

What a Drop Can Do: Dried Blood Spots as a Minimally Invasive Method for Integrating Biomarkers Into Population-Based Research

Logistical constraints associated with the collection and analysis of biological samples in community-based settings have been a significant impediment to integrative, multilevel biodemographic and biobehavioral research. However, recent methodological developments have overcome many of these constraints and have also expanded the options for incorporating biomarkers into population-based health research in international as well as domestic contexts. In particular, using dried blood spot (DBS) samples—drops of whole blood collected on filter paper from a simple finger prick— provides a minimally invasive method for collecting blood samples in nonclinical settings. After a brief discussion of biomarkers more generally, we review procedures for collecting, handling, and analyzing DBS samples. Advantages of using DBS samples—compared with venipuncture—include the relative ease and low cost of sample collection, transport, and storage. Disadvantages include requirements for assay development and validation as well as the relatively small volumes of sample. We present the results of a comprehensive literature review of published protocols for analysis of DBS samples, and we provide more detailed analysis of protocols for 45 analytes likely to be of particular relevance to population-level health research. Our objective is to provide investigators with the information they need to make informed decisions regarding the appropriateness of blood spot methods for their research interests.

Longitudinal evidence that fatherhood decreases testosterone in human males

In species in which males care for young, testosterone (T) is often high during mating periods but then declines to allow for caregiving of resulting offspring. This model may apply to human males, but past human studies of T and fatherhood have been cross-sectional, making it unclear whether fatherhood suppresses T or if men with lower T are more likely to become fathers. Here, we use a large representative study in the Philippines (n = 624) to show that among single nonfathers at baseline (2005) (21.5 ± 0.3 y), men with high waking T were more likely to become partnered fathers by the time of follow-up 4.5 y later (P < 0.05). Men who became partnered fathers then experienced large declines in waking (median: −26%) and evening (median: −34%) T, which were significantly greater than declines in single nonfathers (P < 0.001). Consistent with the hypothesis that child interaction suppresses T, fathers reporting 3 h or more of daily childcare had lower T at follow-up compared with fathers not involved in care (P < 0.05). Using longitudinal data, these findings show that T and reproductive strategy have bidirectional relationships in human males, with high T predicting subsequent mating success but then declining rapidly after men become fathers. Our findings suggest that T mediates tradeoffs between mating and parenting in humans, as seen in other species in which fathers care for young. They also highlight one likely explanation for previously observed health disparities between partnered fathers and single men.

Psychosocial and behavioral predictors of inflammation in middle-aged and older adults : The chicago health, aging, and social relations study

Objective: C-reactive protein (CRP) is emerging as an important predictor of cardiovascular disease (CVD), and chronic inflammation may be a mechanism through which stress affects disease risk. We investigated the contribution of behavioral and psychosocial factors to variation in CRP concentrations in a population-based sample of middle-aged and older adults. Methods: A high sensitivity enzyme-linked immunosorbent assay (ELISA) validated for use with dried blood spot samples was used to determine CRP concentrations in a representative sample of 188 52- to 70-year-olds. Demographic (gender, ethnicity, socioeconomic status), anthropometric (height, weight, waist circumference, percent body fat), behavioral (alcohol consumption, smoking, sleep quality, dietary quality), and psychosocial data (perceived stress, chronic stress, depressive symptoms, loneliness, perceived social support) were collected on the same day as blood samples. Psychosocial variables collected the year before were also used to investigate the impact of changing psychosocial environments. Log-transformed CRP concentrations were examined in a series of nested multivariate regression models. Results: African American and female participants were found to have higher CRP concentrations, as did individuals with lower levels of education. However, ethnic differences disappeared after the addition of behavioral and psychosocial variables. Waist circumference, latency to sleep, smoking, and perceived stress were independently associated with increased concentrations of CRP. Conclusions: Psychosocial stress, as well as health behaviors, are important predictors of inflammatory activity in a population-based sample and should be considered in future research on inflammation and CVD. BMI = body mass index; CRP = C-reactive protein; CVD = cardiovascular disease; ISEL = Interpersonal Support Evaluation List; PSS = Perceived Stress Scale.

Cohort Profile: The Cebu Longitudinal Health and Nutrition Survey

The Cebu Longitudinal Health and Nutrition Survey (CLHNS) was originally conceptualized as an interdisciplinary study of infant-feeding patterns, particularly the overall sequencing of feeding events (milks and complementary foods), the factors affecting feeding decisions and how feeding patterns affect the infant, mother and household. The idea was to study these topics within as natural a setting as possible and to analyse how infant-feeding decisions interacted with social, economic and environmental factors to affect health, nutritional, demographic and economic outcomes. The study was subsequently expanded to cover a wide range of maternal and child health and demographic issues that could be well studied using a prospective, community-based sample. The study was initially the product of collaboration among researchers at the Carolina Population Center at the University of North Carolina at Chapel Hill (led by B.M.P. with J.S.A. and D.K.G.), The Office of Population Studies Foundation at the University of San Carlos in Cebu, Philippines (led by the late Director Wilhelm Fleiger) and the Nutrition Center of the Philippines (led by Florentino Solon). L.S.A. took the lead for follow-up surveys beginning in 1990. Later, the study team was expanded to include researchers presently at the Northwestern University (C.W.K. and T.M.D.) and Johns Hopkins University (M.J.H.). The study was initiated with cooperation and approval from the Cebu Department of Health. The CLHNS website includes a full list of investigators and their affiliations. The CLHNS was one of the first large-scale, population-based surveys designed with a conceptual framework in mind. The guiding framework was adapted from Mosley and Chen’s health determinants model, which posits that underlying community-, householdand individual-level variables affect a set of proximate health behaviours which, in turn, influence health outcomes such as growth and infectious disease morbidity and mortality. The study was designed by a highly interdisciplinary group of economists, sociologists, nutritionists, demographers and physicians. The CLHNS has been funded by a large number of government and non-government organizations (listed in the Funding section).

Epstein-barr virus antibodies in whole blood spots: A minimally invasive method for assessing an aspect of cell-mediated immunity

Objective Study 1: Introduce and validate a method for measuring EBV p18-VCA antibodies in whole blood spots to provide a minimally invasive marker of cell-mediated immune function. Study 2: Apply this method to a large community-based study of psychopathology in children and adolescents. Methods The EBV antibody method was evaluated through analysis of precision, reliability, stability, and comparisons with plasma and indirect immunofluorescence methods. The effects of life events on p18-VCA antibody level were considered in a subsample of 9, 11, and 13 year-old children participating in the Great Smoky Mountains Study in North Carolina. The subsample was stratified by age, sex, and degree of overall life strain. Results Dried blood spots provided a convenient, sensitive, precise, and reliable method for measuring EBV p18-VCA antibody titer. Life events were positively associated with p18-VCA antibodies in girls but not in boys. Conclusions The validity of the blood spot EBV p18-VCA antibody assay, as well as the ease of sample collection, storage, and transportation, may provide an opportunity for psychoneuroimmunology to explore a wider range of stress models in larger, community-based studies.

Early environments and the ecology of inflammation.

Recent research has implicated inflammatory processes in the pathophysiology of a wide range of chronic degenerative diseases, although inflammation has long been recognized as a critical line of defense against infectious disease. However, current scientific understandings of the links between chronic low-grade inflammation and diseases of aging are based primarily on research in high-income nations with low levels of infectious disease and high levels of overweight/obesity. From a comparative and historical point of view, this epidemiological situation is relatively unique, and it may not capture the full range of ecological variation necessary to understand the processes that shape the development of inflammatory phenotypes. The human immune system is characterized by substantial developmental plasticity, and a comparative, developmental, ecological framework is proposed to cast light on the complex associations among early environments, regulation of inflammation, and disease. Recent studies in the Philippines and lowland Ecuador reveal low levels of chronic inflammation, despite higher burdens of infectious disease, and point to nutritional and microbial exposures in infancy as important determinants of inflammation in adulthood. By shaping the regulation of inflammation, early environments moderate responses to inflammatory stimuli later in life, with implications for the association between inflammation and chronic diseases. Attention to the eco-logics of inflammation may point to promising directions for future research, enriching our understanding of this important physiological system and informing approaches to the prevention and treatment of disease.

Early origins of inflammation: microbial exposures in infancy predict lower levels of C-reactive protein in adulthood

Ecological factors are important determinants of the development and function of anti-pathogen defences. Inflammation is a central part of innate immunity, but the developmental factors that shape the regulation of inflammation are not known. We test the hypothesis that microbial exposures in infancy are associated with high sensitivity C-reactive protein (CRP) in adulthood using prospective data from a birth cohort in the Philippines (n = 1461). Lower birth weight was associated with increased CRP, consistent with a role for inflammation in the widely documented inverse relationship between birth weight and adult cardiovascular diseases. In addition, higher levels of microbial exposure in infancy were associated with lower CRP. These associations were independent of socioeconomic status, measures of current body fat and other health behaviours. We conclude that measures of microbial exposure and nutrition during the pre-natal and early post-natal periods are important predictors of CRP concentration in young adulthood. We speculate that the development of anti-inflammatory regulatory networks in response to early microbial exposure represents plasticity in the development of anti-pathogen defences, and that this process may help explain the low CRP concentrations in this population.

Defining the "urban" in urbanization and health: a factor analysis approach

Urban environments have been linked to a range of human health issues, and as the pace of urbanization accelerates, new challenges arise to characterize these environments, and to understand their positive and negative implications for health. We seek to contribute to future studies of urbanization and health by exploring multiple definitions of urbanicity in the Philippines, using data from an ongoing, longitudinal study. We use factor analysis to identify meaningful clusters of household- and community-level variables, and to generate factor scores that summarize each households position with respect to access to infrastructure and health services, and level of affluence. Factor scores are considered for 1983 and 1994 to assess the type and pace of change that has occurred in the Philippines, and scores are compared across urban and rural areas, and across six different settlement types, to explore household- and community-level markers of urbanicity. This analysis demonstrates the heterogeneity of environments within urban and rural areas, and emphasizes the need for a finer level of investigation in future studies of urbanization and health.

Positive youth, healthy adults: Does positive well-being in adolescence predict better perceived health and fewer risky health behaviors in young adulthood?

PURPOSE To examine the prospective, longitudinal associations between positive well-being during adolescence and health outcomes in young adulthood, using a large, nationally representative sample of youth. METHODS On the basis of the data from the first three waves of the National Longitudinal Study of Adolescent Health, we examined positive well-being during adolescence (averaged across Waves I-II) as a predictor of perceived young adult general health and risky health behaviors (Wave III). Each model included a full set of health and demographic baseline covariates. Missing values were assigned using multiple imputation methods (n = 10,147). RESULTS Positive well-being during adolescence was significantly associated with reporting better perceived general health during young adulthood, independent of depressive symptoms. Positive well-being was also significantly associated with fewer risky health behaviors in Wave III, after adding all covariates, including depressive symptoms and baseline risky health behaviors. CONCLUSION Few studies of adolescent health have examined positive psychological characteristics, tending to focus instead on the effect of negative mood states and cognitions on health. This study demonstrates that positive well-being during adolescence predicts better perceived general health and fewer risky health behaviors during young adulthood. Aligned with the goals of the positive youth development perspective, promoting and nurturing positive well-being during the transition from childhood to adolescence may present a promising way to improve long-term health.