Obesity affects pulmonary function in Japanese adult patients with asthma, but not those without asthma

Abstract

Obesity is associated with the severity of asthma, which is characterized by airway obstruction. Pulmonary function testing is one of the important examinations for evaluating airway obstruction. However, the impact of obesity on pulmonary function in patients with asthma is not fully understood. A total of 193 patients with asthma and 2159 patients without asthma who visited Saga University Hospital were investigated retrospectively. Obesity was defined as a body mass index (BMI) greater than 25 kg/m2. Pulmonary functions including forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were compared between patients with and without asthma, focusing especially on obesity. FVC percent predicted and FEV1 percent predicted were significantly lower in patients with asthma than in those without asthma (p = 0.03, < 0.01 respectively). In patients with asthma, FVC percent predicted and FEV1 percent predicted were significantly lower in patients with obesity than in those without obesity (all p < 0.01). In addition, BMI was negatively correlated with FEV1 (r =− 0.21, p = 0.003) and FVC (r = − 0.15, p = 0.04), along with the percent predicted. On multivariate analysis in patients with asthma, FVC (β [95% confidence interval] 0.12 [0.02–0.22], p = 0.02) and FEV1 (0.13 [0.05–0.22], p < 0.01) were still significantly different between patients with and without obesity. However, these obesity-associated differences were not observed in patients without asthma. Obesity reduces pulmonary function, including FVC and FEV1, in patients with asthma, but not in those without asthma.

Pulmonary and chest wall function in obese adults

“…Taken together, in the absence of other respiratory pathology or condition or morbidity obesity seems not to have a systematical restrictive effect on the lung. This speculation is supported by a recent study that concluded that obesity affects pulmonary function in Japanese adult patients with asthma, but not those without asthma 53 . On the other hand, even in the absence of other respiratory pathology or condition or morbidity obesity seems to have a systematical restrictive effect on the ribcage.…”

Obesity-related asthma: new insights leading to a different approach

“…This effect is most pronounced in the functional residual capacity (FRC) and expiratory reserve volume (ERV), while it has only small effects on the total lung capacity (TLC) [19,20,21,22 ▪ ]. During dynamic lung function tests, forced expiratory volume (FEV1) and forced vital capacity (FVC) are reduced while the FEV1/FVC ratio is usually unaffected [19,22 ▪ ,23–25]. However, in patients with comorbid metabolic syndrome, the FEV1/FVC ratio decreases because of increased abdominal circumference (which is a major criterion for metabolic syndrome and may influence airway diameter as well), greater tobacco exposure, and elevated eosinophils indicating low-grade systemic inflammation [26].…”

Does the level of obesity impact on the respiratory function in adults?

“…Saliman et al concluded that in morbidity obesity restrictive ventilatory defects were less common than obstructive ventilatory patterns [49]. Maybe obesity affects pulmonary function in concomitant with other morbidities, particularly asthma [50].…”