Weight Change from Early to Middle Adulthood and Incident Asthma Later in Life: A Retrospective Cohort Study

Abstract Background: Data describing the effects of weight change across adulthood on asthma are important for the prevention of asthma. This study aimed to investigate the association between weight change from early to middle adulthood and risk of incident asthma.Methods: Using data from the National Health and Nutrition Examination Survey (NHANES), we performed a nationally retrospective cohort study of the U.S. general population. A total of 20 771 people aged 40-74 years with recalled weight at young and middle adulthood were included in the cohort. Hazard ratios relating weight change to incident asthma over 10 years of follow-up were calculated using Cox models adjusting for covariates.Results: Compared with participants with stable non-obesity between young and middle adulthood, the hazard ratios of incident asthma were 1.63 (95% confidence interval 1.29 to 2.07) for weight gain (non-obesity to obesity), 1.41 (0.97 to 2.05) for stable obesity, and 1.21 (0.41 to 3.62) for weight loss (obesity to non-obesity). In addition, participants who gained more than 20 kg had a hazard ratio of 1.53 (1.15 to 2.03), compared with those whose weight had remained stable. When stratified by sex, the association between weight gain and incident asthma was seen only in females. Population attributable fraction calculations estimated that 10.2% of adult-onset asthma could be averted, if all those who were non-obesity at early adulthood could prevent weight gain by midlife. Conclusion: The findings implied that maintaining normal weight across adulthood, especially preventing weight gain in early adulthood, was important for preventing adult-onset asthma.