Association between body composition and subsequent childhood asthma and wheeze outcomes in the Southampton Women's Survey cohort study

Abstract

BackgroundObesity is associated with adult asthma, notably non-atopic asthma. The association between obesity and childhood asthma is unclear and complicated by changes in body composition during growth. We aimed to determine whether and how body composition and change in body composition are associated with childhood asthma, wheeze, and atopic outcomes. MethodsParticipants were 940 children born between February, 2000, and June, 2003, to women recruited within the Southampton Women's Survey. Body composition was characterised with body-mass index (BMI) at 3 years and 6 years of age, standardised for age and sex; lean and fat mass measured at 4 years and 6 years of age with dual energy X-ray absorptiometry (DEXA) scanning; and serial measures of subscapular skinfold thickness. Relative risks were calculated with Poisson regression for questionnaire-determined asthma and wheeze at age 6 years. Wheeze was defined as atopic or non-atopic according to skin prick testing. Spirometry, bronchial hyper-responsiveness (BHR), and fractional exhaled nitric oxide (FeNO) were assessed at 6 years of age. Potential maternal and socioeconomic confounders were adjusted for and exposure variables combined in multivariable models. Written informed parental consent was obtained for each participant. The study was approved by the Southampton and South West Hampshire Local Research Ethics Committee. FindingsBMI at 6 years of age was not associated with asthma, atopy, any wheeze phenotype, or measure of lung function. Higher BMI at age 3 years was associated with greater BHR at age 6 (p=0·032) and with lower forced expiratory volume in the first second of expiration corrected for lung size by dividing by forced vital capacity (FEV1/FVC) (p=0·013). Although a conditional increase in subscapular skinfold thickness between 1 and 2 years was associated with asthma at age 6 years (relative risk 1·27, 95% CI 1·07–1·51), a decrease in subscapular skinfold thickness between 2 and 3 years was associated with increased risks of asthma (0·73, 0·55–0·96), wheeze, atopy, and atopic wheeze at age 6 years and with greater FeNO. InterpretationCurrent BMI at 6 years was not associated with asthma symptoms or impaired lung function in this cohort of children at age 6 years, although a higher BMI at age 3 years was associated with increased BHR and reduced FEV1/FVC at age 6 years. More rapid adiposity gain between ages 1 and 2 years was associated with increased asthma risk; although this finding might be an adverse effect of increased adiposity on respiratory development, rapid postnatal adiposity gain might be catch-up growth and might be a marker for adverse in-utero factors. By contrast, lower adiposity gain between 2 and 3 years was associated with asthma and markers of atopy and eosinophilic airway inflammation, suggesting that factors associated with poor weight gain in this period, such as recurrent respiratory infection, might predispose to atopic sensitisation. FundingMedical Research Council, British Heart Foundation, Food Standards Agency, Arthritis Research UK, National Osteoporosis Society, International Osteoporosis Foundation, Cohen Trust, NIHR Southampton Biomedical Research Centre, NIHR Oxford Biomedical Research Unit, British Lung Foundation.