Obesity and All-Cause Mortality Among Black Adults and White Adults
Sarah S. Cohen
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Lisa B. Signorello
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Elizabeth L. Cope
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Joseph K. McLaughlin
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Margaret K. Hargreaves
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Wei Zheng
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William J. Blot
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Abbreviations: BMI, body mass index; CI, confidence interval; HR, hazard ratio; ICD-10,
International Classification of Diseases
, Tenth Revision; SCCS,
Southern Community Cohort Study
American Journal of Epidemiology The Author 2012. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: . In recent pooled analyses among whites and Asians, mortality was shown to rise markedly with increasing body mass index (BMI; weight (kg)/height (m)2), but much less is known about this association among blacks. This study prospectively examined all-cause mortality in relation to BMI among 22,014 black males, 9,343 white males, 30,810 black females, and 14,447 white females, aged 40-79 years, from the Southern Community Cohort Study, an epidemiologic cohort of largely low-income participants in 12 southeastern US states. Participants enrolled in the cohort from 2002 to 2009 and were followed up to 8.9 years. Hazard ratios and 95% confidence intervals for mortality were obtained from sex- and race-stratified Cox proportional hazards models in association with BMI at cohort entry, adjusting for age, education, income, cigarette smoking, and alcohol consumption. Elevated BMI was associated with increased mortality among whites (hazard ratios for BMI >40 vs. 20-24.9 = 1.37 (95% confidence interval (CI): 1.02, 1.84) and 1.47 (95% CI: 1.15, 1.89) for white males and white females, respectively) but not significantly among blacks (hazard ratios = 1.13 (95% CI: 0.89, 1.43) and 0.87 (95% CI: 0.72, 1.04) for black males and black females, respectively). In this large cohort, obesity in midto-late adulthood among blacks was not associated with the same excess mortality risk seen among whites. African Americans; body mass index; mortality
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The rise in obesity levels in the general population over
the past 3 decades (13) is expected to result in enormous
health burdens and health-care costs as obesity is linked to
many adverse health outcomes, including diabetes,
cardiovascular disease, cancer, and overall mortality (46).
Recent pooled cohort analyses have reported a J-shaped
relation between body mass index (BMI) and all-cause
mortality with more than doubled mortality risks among
extremely obese whites (6, 7) and parallel but less
pronounced risks among East Asians (8). Some previous
studies have found a weaker obesity-mortality association
among African Americans (914), but few studies have
examined this question in large populations of African
Americans, and none have been concentrated in low-income
populations or in the southeastern United States where the
obesity epidemic is pronounced (15). Our objective
therefore was to prospectively examine the association between
BMI and all-cause mortality in the Southern Community
Cohort Study (SCCS), a unique cohort with a large
African-American population as well as a sizeable group of
socioeconomically comparable whites.
MATERIALS AND METHODS
Study participants
The SCCS is a prospective cohort study assessing
disparities in chronic diseases among adults in urban and rural
areas in 12 southeastern US states (1618). From 2002 to
2009, nearly 86,000 adults were enrolled in the cohort,
most (86%) at one of 71 participating community health
centers that provide basic health services mainly to
lowincome and uninsured persons (19). An additional 14% of
the cohort enrolled from 2004 to 2006 by responding to a
mailed questionnaire sent to randomly selected residents of
the same 12 states. SCCS participants were required to be
4079 years of age, to speak English, and not to be under
treatment for cancer in the 12 months preceding cohort
enrollment. The enrollment protocol was designed so that
overall approximately two-thirds of participants would be
black. The SCCS was approved by institutional review
boards at Vanderbilt University and Meharry Medical
College, and all participants provided written, informed
consent.
Data collection and BMI assessment
Participants completed a baseline survey (via in-person
interview for community health center enrollees and a
self-administered questionnaire for mail enrollees) at
enrollment. This survey, available online (18), contained
questions about demographic, medical, familial, lifestyle, and
other participant characteristics. Race was self-reported.
Current weight and height were self-reported in the baseline
survey through September 2007 and, in addition, for 25%
of the community health center participants, height and
weight measured on the day of the baseline interview were
abstracted from community health center medical records.
Starting in October 2007, height and weight were measured
for all community health center participants by trained
interviewers using a SECA 703 digital scale (SECA Corp.,
Hanover, M (...truncated)