Associations of body fat percent and body mass index with childhood asthma by age and gender
Journal
Obesity
Date Issued
January 2, 2013
DOI
10.1002/oby.20284
Abstract
Objective: High body mass index (BMI) has been shown to be associated with asthma, but the pattern
of this association is still unclear and may differ by gender or stage of puberty. BMI is only a proxy of
adiposity, whereas estimation of body fat percent (BF%) by the bioimpedance technique is considered
an accurate measure of adiposity. We investigated whether BMI and BF% behave differently in their
association with asthma between genders, before and during adolescence.
Design and Methods: In this cross-sectional study of 10,981 schoolchildren, we used logistic regression
models to examine the pattern of association of BMI and BF% with asthma.
Results: In the case of BF%, both the highest (odds ratio [OR]: 1.68, 95% confidence interval [95% CI]:
1.21-2.30) and lowest (OR: 1.59, 95% CI: 1.13-2.23) z-score categories conferred an increased adjusted
risk for active asthma. The likelihood ratio test (LRT) of nonlinearity yielded significant results (P < 0.01)
for BF%. In contrast, the LRT for BMI yielded a nonsignificant result (P ¼ 0.45) indicating a linear
association of asthma with BMI. A unit increase in BMI z-score conferred an increase in the adjusted
odds of active asthma (OR: 1.14, 95% CI: 1.02-1.27). In the case of BF%, the adjusted ORs for active
asthma at the highest and lowest z-score categories in both genders, before and during adolescence,
were similarly elevated, exhibiting a U-shape pattern.
Conclusions: In contrast to the linear association observed with BMI, BF% displayed a U-shaped
association with asthma and may be the preferred measure of adiposity in epidemiological studies of
asthma in children.
of this association is still unclear and may differ by gender or stage of puberty. BMI is only a proxy of
adiposity, whereas estimation of body fat percent (BF%) by the bioimpedance technique is considered
an accurate measure of adiposity. We investigated whether BMI and BF% behave differently in their
association with asthma between genders, before and during adolescence.
Design and Methods: In this cross-sectional study of 10,981 schoolchildren, we used logistic regression
models to examine the pattern of association of BMI and BF% with asthma.
Results: In the case of BF%, both the highest (odds ratio [OR]: 1.68, 95% confidence interval [95% CI]:
1.21-2.30) and lowest (OR: 1.59, 95% CI: 1.13-2.23) z-score categories conferred an increased adjusted
risk for active asthma. The likelihood ratio test (LRT) of nonlinearity yielded significant results (P < 0.01)
for BF%. In contrast, the LRT for BMI yielded a nonsignificant result (P ¼ 0.45) indicating a linear
association of asthma with BMI. A unit increase in BMI z-score conferred an increase in the adjusted
odds of active asthma (OR: 1.14, 95% CI: 1.02-1.27). In the case of BF%, the adjusted ORs for active
asthma at the highest and lowest z-score categories in both genders, before and during adolescence,
were similarly elevated, exhibiting a U-shape pattern.
Conclusions: In contrast to the linear association observed with BMI, BF% displayed a U-shaped
association with asthma and may be the preferred measure of adiposity in epidemiological studies of
asthma in children.
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