Relationship between childhood body mass index and young adult asthma

The relationship between obesity and asthma is an area of debate.

To investigate the association of elevated body mass index (BMI) at a young age and young adult asthma.

BMI, questionnaires, and serologic tests results were analyzed in participants of a predominantly white, middle-class, population-based birth cohort from Detroit, Michigan at 6 to 8 and 18 years of age. Asthma diagnosis was based on medical record data. Allergen specific IgE was analyzed using UniCAP, with atopy defined as 1 or more allergen specific IgE levels of 0.35 kU/L or higher. Overweight was defined as a BMI in 85th percentile or higher.

A total of 10.6% of overweight males at 6 to 8 years of age had current asthma at 18 to 20 years of age compared with 3.2% of males who were normal or underweight (relative risk [RR], 3.3; 95% confidence interval [CI], 1.0-11.0; P=.048). A total of 19.6% of females who were overweight at 6 to 8 years of age had asthma compared with 10.3% of females who were normal or underweight (RR, 1.9; 95% CI, 0.9-3.9; P=.09). After adjustment for atopy at 6 to 8 years of age, overweight males had an adjusted RR of 4.7 (95% CI, 1.4-16.2; P=.01), and overweight females had an adjusted RR of 1.7 (95% CI, 0.8-3.3; P=.15). Change in BMI between 6 to 8 years of age and 18 to 20 years of age was also examined. Patients with persistently elevated BMI exhibited increased risk of asthma as young adults (RR, 2.4; 95% CI, 1.2-4.7) but not with an increasing BMI (RR, 0.8; 95% CI, 0.3-2.2) or a decreasing BMI (RR, 0.8; 95% CI, 0.3-2.2).

Overweight males 6 to 8 years of age have increased risk of asthma as young adults. Being overweight remains a predictor of asthma after adjustment for early atopy. A similar but not statistically significant trend was also seen among overweight females. Overweight body habitus throughout childhood is a risk factor for young adult asthma.