High BMI Negatively Impacts Patients With COPD and Asthma

According to a recent study, a high body mass index (BMI) greatly affects the diagnosis and severity of chronic obstructive pulmonary disease (COPD) and asthma. The study was published Frontiers of Physiology.

To investigate the influence of BMI on spirometry indices in patients with COPD and asthma, investigators reviewed data from patients with COPD or asthma who underwent bronchodilator tests (BDTs) between 2017 and 2021. BMI categories were defined as underweight (BMI <18.5 kg/m²), normal weight (≥18.5 to <25 kg/m²), overweight (≥25 to <30 kg/m²), and obese (≥30 kg/m²). Spirometry indices, including pre- and post-forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC ratio, were compared across these BMI categories.

The analysis included 3891 patients with COPD (average age, 66.5 years) and 1208 with asthma (average age, 59.7 years). Among COPD patients, those classified as underweight exhibited significantly lower values for pre- and post-FEV₁ (L, %), pre- and post-FVC (L, %), and pre- and post-FEV₁/FVC compared with normal-weight individuals (all P<.05). Conversely, overweight and obese patients with COPD showed higher values for these spirometry indices.

In the asthma cohort, underweight patients demonstrated lower pre- and post-FEV₁ (L, %), pre- and post-FVC (L, %), and pre- and post-FEV₁/FVC compared with their normal-weight counterparts. Obese patients with asthma displayed higher pre- and post-FEV₁/FVC ratios (all P<.05).

The investigators acknowledged several limitations to their study. “Firstly, the data we used was all acquired from BDTs. Since most of the time BDT was completed when FEV₁ [was] <70%, subjects with normal or [mildly severe] ventilatory dysfunction would be mostly excluded,” they noted. “As a result, we could not know the effect of BMI on these populations.” Furthermore, the study’s scope was restricted to evaluating the impact of BMI on spirometry indices in individuals diagnosed with COPD and asthma. The omission of conditions such as bronchiectasis and cystic fibrosis limits the study’s ability to provide a comprehensive understanding of how BMI categories may influence spirometry outcomes in a broader spectrum of chronic respiratory diseases.

“Pulmonologists and physicians should pay attention to these effects to better diagnose and manage patients. Maintaining a suitable BMI is important for patients with asthma or COPD. Weight maintenance should be embedded in the management of these illnesses,” the investigators concluded.