Obesity and weight change during eight years in relation to asthma incidence

Obesity has been associated with increased prevalence of asthma in cross-sectional studies. We aim to examine the relation of obesity and weight change to 8-year asthma incidence in a randomly selected population-based adult cohort. West Sweden asthma study survey was performed in 2008 (18,087 participated) and follow-up in 2016 (12,449 participated). Participants responded to a questionnaire on these two occasions. Obesity was defined as body mass index (BMI) ≥ 30 (kg/m²), and overweight as 25 ≤ BMI < 30 (kg/m²). Asthma was defined with affirmative answer to the question "Have you been diagnosed with asthma by a physician?". Asthma incidence was reported per 1000 person-year over the 8-year follow-up period. Among participants without asthma (N = 10,769) in 2008, asthma incidence was 1.8 per 1000 person-year. Asthma incidence was higher in 40-60 years old, normal, or overweight participants who gained ≥ 4 BMI (kg/m²), or in those who were obese with a stable BMI. Asthma incidence sharply increased in those who gained ≥ 4 BMI (kg/m²), especially in women. Additionally, the risk of asthma was significantly higher in a dose-dependent manner among those who gained ≥ 0.5 BMI (kg/m²) compared to those with stable, normal weight. The risk of asthma was higher in those who were obese at baseline regardless of their weight change than individuals with stable, normal weight. Our findings highlight the necessity for health care to integrate weight management strategies as a key component of asthma prevention and care, particularly for women in middle age who are overweight or obese.