Obesity-associated severe asthma in an adult Japanese population.

Background: Severe asthma is increasingly being recognized as an important public health issue. Obesity has been identified as a risk factor for poor asthma control and for worsening of asthma severity. However, most studies investigating obese patients with asthma have been performed in Western countries. Reports on the characteristics of obese Japanese individuals with severe asthma are lacking. Herein, we investigated the clinical characteristics of patients with obesity-associated severe asthma in a Japanese population and the association between obesity and poor asthma control.

Methods: We conducted a retrospective observational study of adult patients with severe asthma. Patients were classified into two groups based on the definition of obesity recommended by the Japan Society for the Study of Obesity: obese (OB) group (body mass index [BMI] ≥25 kg/m) and non-obese (NOB) group (BMI <25 kg/m). The two groups were compared. The characteristics of obesity and the metabolic functions are known to differ between males and females; therefore, we analyzed male-only and female-only cohorts separately.

Results: A total of 492 patients were enrolled. Age, smoking history in terms of number of pack-years, daily controller medications use, and spirometric data were not significantly different between the OB and NOB groups in either cohort. In the female cohort, the annual exacerbation ratio and the percentage of frequent exacerbators were significantly higher in the OB group compared to the NOB group. A multivariate logistic regression analysis showed that obesity was independently associated with frequent asthma exacerbations in the female cohort.

Conclusions: Our study revealed that obesity, defined as a BMI ≥25 kg/m, was independently associated with poor asthma control (including acute exacerbations) in adult Japanese females with severe asthma.