Airway Obstruction Worsens in Young Adults with Asthma Who Become Obese

Background: Few studies have examined how developing obesity in early adulthood affects the course of asthma. Objective: We analyzed lung function and asthma impairment and risk among nonobese children with asthma, comparing those who were obese in young adulthood with those who remained nonobese. Methods: We carried out the post hoc analysis of 771 subjects with mild to moderate asthma who were not obese (pediatric definition, body mass index [BMI] < 95th percentile) when enrolled in the Childhood Asthma Management Program at ages 5-12 years. The subjects were then followed to age 20 years or more. For visits at ages 20 years or more, spirometry values as percent predicted and recent asthma symptom scores and prednisone exposure were compared between 579 subjects who were nonobese at all visits and 151 who were obese (adult definition of BMI ≥ 30 kg/m²) on at least 1 visit (median number of visits when obese = 4, IQR 2-7). Results: Compared with participants who were nonobese (BMI 23.4 ± 2.6 kg/m²), those who became obese (BMI 31.5 ± 3.8 kg/m²) had significant decreases in forced expiratory volume in the first second (FEV₁)/forced vital capacity (FVC) (P < .0003) and FEV₁ (P = .001), without differences in FVC (P = .15) during visits at ages 20 years or more. For each unit increase of BMI, FEV₁ percent predicted decreased by 0.29 (P = .0009). The relationship between BMI and lung function was not confounded by sex or BMI at baseline. Asthma impairment (symptom scores) and risk (prednisone use) did not differ between the 2 groups. Conclusion: Becoming obese in early adulthood was associated with increased airway obstruction, without impact on asthma impairment or risk.