Asthma Symptoms, BMI Linked With Exercise Capacity in Patients With Severe Asthma

Asthma control and body mass index (BMI) were 2 factors shown to be significantly correlated with exercise capacity, as measured by walking distance, in patients with severe asthma, according to a recent study published in Respirology. However, when each sex was analyzed separately, this correlation remained statistically significant for females, but not males.

Researchers aimed to investigate possible associations between various factors and exercise capacity in patients with severe asthma, and if these associations are affected by sex. It is important to determine variables that may affect exercise capacity as exercise is an important factor associated with health-related quality of life and asthma symptom management, the researchers noted.

This cross-sectional study included 137 patients diagnosed with severe asthma. Patients were recruited for the study from John Hunter Hospital in Australia; 85 (63.5%) patients were female, and the median age was 89 years.

To evaluate patients’ exercise capacity, researchers conducted a 6-minute walk test (6MWT) in order to measure patients’ 6-minute walk distance (6MWD).

Researchers also assessed patients’ height, weight, isometric leg strength, lung function (before and after the 6MWT) and systemic inflammation.

The 5-item Asthma Control Questionnaire (ACQ-5) assessed patients’ asthma control by asking questions related to symptoms and activity limitations. A score change of 0.5 points or larger signifies a clinically importance difference. The Juniper Asthma Quality of Life questionnaire measured patients’ health status.

Accounting for the whole study population (males and females), multiple linear regression analyses revealed that an increase of 0.5 points on the ACQ-5 was correlated with a reduction of 15.2m in 6MWD, and an increase of 1 unit in BMI was correlated with a reduction of 3.2m in 6MWD.

For females, an increase of 0.5 points on the ACQ-5 was correlated with a reduction of 14.5 in 6MWD. Asthma control was not significantly correlated with walk distance in males.

For females, an increase of 1 unit in BMI was correlated with a reduction of 4.0m in 6MWD. BMI was not significantly correlated with walk distance in males.

Asthma control and BMI remained significantly correlated to 6MWD in females with severe asthma, but not in males. Multiple linear regression analysis showed only age to be significantly associated with 6MWD in males.

Limitations of this study include the cross-sectional study design, which prohibits researchers from determining causality among the factors analyzed. The researchers note that the relationships determined between asthma control and BMI on exercise capacity may be bidirectional.

The findings indicate possible targets for improvement in order to increase exercise capacity and gain positive health outcomes, the researchers concluded.

Reference

Pitzner-Fabricius A, Clark VL, Backer V, Gibson PG, McDonald VM. Factors associated with 6-min walk distance in severe asthma: a cross-sectional study. Respirology. Published online July 10,2022. doi:10.1111/resp.14323