The impact of low forced vital capacity on behavior restrictions in a population with airflow obstruction

Recent studies have suggested that low forced vital capacity (FVC) is related to respiratory symptoms with various comorbid conditions that eventually lead to physical inactivity and may be applied to subjects with airflow obstruction (AO). Therefore, this study aimed to evaluate the association between low FVC and behavior restrictions in subjects with AO.

A cross-sectional study was performed using data from the Korea National Health and Nutrition Survey conducted between 2007 and 2015. Participants aged 40 to 79 years with spirometry-defined AO (pre-bronchodilator forced expiratory volume in one second/FVC <70%) were analyzed to evaluate the association between low FVC (defined as FVC <80% predicted) and behavior restrictions.

A total of 3,345 participants with AO were included. The proportion of subjects with low FVC varied widely according to severity of airflow limitation (0.9%, 35.5%, and 85.1% in the mild, moderate, and severe-to-very-severe AO groups, respectively). Compared to the moderate AO group with normal FVC, those with low FVC were more likely to be older, to be never- or ex-smokers, to have larger waist size with higher body mass index, and to have comorbidities such as diabetes, hypertension, dyslipidemia, and osteoporosis. Low FVC was independently associated with behavior restrictions [adjusted prevalence ratio (aPR), 1.72; 95% confidence interval (CI), 1.43-2.06] among all participants with AO, and this was most prominent in those with moderate AO (aPR, 1.65; 95% CI, 1.27-2.13).

In subjects with moderate AO, low FVC was independently associated with behavior restrictions even after adjusting for confounding factors.