Obesity, insulin resistance and the prevalence of atopy and asthma in US adults.
BACKGROUND
The roles of obesity and insulin resistance in asthma and atopy are not well understood. We investigated whether there is an association of obesity and insulin resistance with asthma and atopy prevalence in US adults.


METHODS
Data from the 2005-2006 National Health and Nutrition Examination Survey were analyzed by multivariate logistic regression, controlling for sex, age, ethnicity, income, and smoking status. Obesity was measured by body mass index (BMI) and waist circumference, and insulin resistance by the homeostasis model assessment. Asthma was defined by self-report of ever receiving a diagnosis and still having asthma currently, and atopy by any positive specific serum IgE responses to a panel of aeroallergens.


RESULTS
Neither obesity measure nor insulin resistance was associated with atopy. Obesity was positively associated with asthma overall (odds ratio [OR] for obese vs normal BMI = 2.28, 95% CI: 1.76, 2.96; OR for obese vs normal waist circumference = 1.75; 95% CI: 1.22, 2.51) but insulin resistance was not (OR = 1.26; 95% CI: 0.80, 1.98). Obesity was also associated with nonatopic asthma (OR for obese vs normal BMI = 2.5; 95% CI: 1.2, 5.2; OR for obese vs normal waist circumference = 2.07, 95% CI: 1.21, 3.54), while obese BMI was also associated with atopic asthma (OR = 2.04, 95% CI: 1.37, 3.03). Obesity remained independently associated with all asthma outcomes after controlling for insulin resistance.


CONCLUSIONS
Obesity was independently associated with asthma, and atopic and nonatopic asthma, after controlling for insulin resistance and socio-demographic factors. There was no evidence that insulin resistance was associated with atopy or asthma.
Ma
J
J
Department of Health Services Research, Palo Alto Medical Foundation Research Institute, Palo Alto, CA, USA. maj@pamfri.org
Xiao
L
L
Knowles
S B
SB
D000328:Adult; D000368:Aged; D001249:Asthma / Q000150:complications* / Q000453:epidemiology*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000150:complications* / Q000453:epidemiology*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D016017:Odds Ratio; D015995:Prevalence; D014481:United States; D055105:Waist Circumference; D055815:Young Adult