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<h5 class="section-title" id="d1591060e260">Question</h5>
<p id="d1591060e262">Does exposure to communities with higher rates of obesity increase
the body mass index
(BMI) and risk of overweight/obesity of individual residents?
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<h5 class="section-title" id="d1591060e265">Findings</h5>
<p id="d1591060e267">Using data from military service members assigned to installations
around the country,
this study found that exposure to counties with higher rates of obesity (relative
to
counties with lower obesity rates) was associated with higher mean BMI and greater
odds
of obesity in parents and higher BMI
<i>z</i> scores and greater odds of
overweight/obesity in children. Associations were stronger among families who had
resided longer in a given location and with off-installation residence; no evidence
supported self-selection or shared built environment as explanations for these
results.
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<h5 class="section-title" id="d1591060e273">Meaning</h5>
<p id="d1591060e275">Exposure to communities with higher rates of obesity is associated
with higher BMI
and
greater risk of overweight and/or obesity in parents and children, and this may suggest
the presence of social contagion.
</p>
</div><p class="first" id="d1591060e278">This study assesses whether exposure to communities
with higher rates of obesity
increases the body mass index and odds of overweight/obesity in individuals and determines
through what mechanisms differences arose.
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<h5 class="section-title" id="d1591060e282">Importance</h5>
<p id="d1591060e284">Little is known about whether the substantial clustering of obesity
and overweight
within social and geographic networks results from causal pathways, such as social
contagion and shared environments, or from self-selection.
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<h5 class="section-title" id="d1591060e287">Objectives</h5>
<p id="d1591060e289">This study aimed to determine whether exposure to communities
with higher rates of
obesity increases the body mass index (BMI) of individuals, calculated as weight in
kilograms divided by height in meters squared, and their risk of being overweight
or
obese, and whether social contagion, shared environments, or self-selection can account
for identified differences.
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<h5 class="section-title" id="d1591060e292">Design, Setting, and Participants</h5>
<p id="d1591060e294">This natural experiment study used the routine assignment of
military service members
to installations as a source of exogenous variation in exposure to communities with
higher vs lower rates of obesity. The study, which used data collected by the Military
Teenagers' Environments, Exercise, and Nutrition Study, examined families from 38
military installations around the United States to determine if individuals had higher
BMI and greater odds of overweight and obesity when assigned to installations in
counties with higher rates of obesity. The study also examined if the relationship
persisted after controlling for shared built environments. The participants included
1
parent and 1 child aged 12 or 13 years from 1519 families of Army-enlisted personnel.
Data analysis was completed from November 2016 to October 2017.
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<h5 class="section-title" id="d1591060e297">Exposures</h5>
<p id="d1591060e299">Adult obesity rate in the county where the assigned installation
of the service member
was located. Time at installation and location of residence (on-installation vs
off-installation) were used to measure the degree of exposure.
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<h5 class="section-title" id="d1591060e302">Main Outcomes and Measures</h5>
<p id="d1591060e304">For parents, outcomes were BMI, overweight/obesity (BMI, ≥25)
and obesity (BMI,
≥30). For children, outcomes were BMI
<i>z</i> score, overweight/obesity
(BMI percentile for age and sex, ≥85), and obesity (BMI percentile for age and
sex, ≥95). These outcomes were based on self-reports for parents, self-reports and
parent reports for all children, and anthropometric measurements for a subsample of
children.
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<h5 class="section-title" id="d1591060e310">Results</h5>
<p id="d1591060e312">Members of 1519 families participated, including 1314 adults
(of whom 740, or 56%,
were
fathers) and 1111 children (of whom 576, or 52%, were boys); anthropometric measurements
were performed on 458 children. The sample was 40% white, 22% black, 24% Hispanic,
and
14% other races/ethnicities. A 1–percentage point higher county obesity rate was
associated with a higher BMI (a difference of 0.08; 95% CI, 0.02-0.13) and greater
odds
of obesity (adjusted odds ratio [aOR], 1.05; 95% CI, 1.02-1.08) in parents, and a
higher
BMI
<i>z</i> score (0.01; 95% CI, 0.003-0.02) and greater odds of
overweight/obesity (aOR, 1.04; 95% CI, 1.01-1.06) in children. The evidence supported
stronger associations among families with more time at installation and off-installation
residence. Associations persisted even after controlling for shared built
environments.
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<h5 class="section-title" id="d1591060e318">Conclusions and Relevance</h5>
<p id="d1591060e320">Exposure to counties with higher rates of obesity was associated
with higher BMI and
higher odds of overweight and/or obesity in parents and children. There was no evidence
to support self-selection or shared built environments as possible explanations, which
suggests the presence of social contagion in obesity.
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