U-shaped association between body mass index and the prevalence of wheeze and asthma, but not eczema or rhinoconjunctivitis: the ryukyus child health study.

BACKGROUND: Studies reporting on the association between obesity and allergies have mostly focused on asthma. Little is known about the relationship of obesity to other allergic diseases, and the information that is available has been inconsistent. We examined the association between body mass index (BMI) and the prevalence of wheeze, asthma, eczema, and rhinoconjunctivitis in Japanese schoolchildren.

METHODS: Study subjects were 24,399 children aged 6-15 years in Okinawa, Japan. Outcomes were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. BMI was categorized into five groups; <5th, 5th to 35th, >35th to 65th, >65th to 95th, and >95th percentile groups. Adjustment was made for sex, age, region of residence, number of siblings, smoking in the household, physical activity, paternal and maternal history of allergic disorders, and paternal and maternal educational levels.

RESULTS: The prevalence values of wheeze, asthma, eczema, and rhinoconjunctivitis in the previous 12 months were 10.8%, 7.6%, 6.9%, and 7.6%, respectively. Compared with the referent category (>35th to 65th percentile group), higher percentile categories were positively associated with the prevalence of wheeze. A U-shaped relationship between BMI and asthma was observed. No material associations between BMI percentile categories and the prevalence of eczema or rhinoconjunctivitis were found.

CONCLUSION: These findings suggested that being either underweight or overweight might increase the likelihood of asthma among Japanese schoolchildren.