Decreased respiratory function associated with aging leads to the onset of chronic obstructive pulmonary disease (COPD) and increased risk of death in the elderly. Prevention of a decline in respiratory function from a young age is important. This study aimed to clarify the factors that affect decreased forced expiratory volume in one second (FEV1)/forced vital capacity (FVC), an index of obstructive respiratory disorder caused by airway obstruction, by considering the influence of body composition and lifestyle. We recruited 262 employed adult men and determined their lifestyle-related factors, including smoking status, past or current secondhand smoke (SHS) exposure, exposure to SHS outside the home, and physical activity (PA). Body composition and respiratory function were also measured. The data were then compared with those of non-smokers using logistic regression analysis, adjusting for age. We also investigated factors influencing FEV1/FVC using multiple regression analysis, adjusting for age, height, smoking status, and lifestyle. Current smokers and heavy smokers exhibited significantly lower amounts of PA and had a higher body fat%, visceral fat area, prevalence of cohabitation with smokers, and frequency of SHS exposure outside the home, and FEV1/FVC was significantly lower in heavy smokers. A multiple regression analysis revealed that FEV1/FVC was associated only with the frequency of SHS exposure outside the home. It is important for occupational health personnel of a company to advise both non-smokers and smokers to avoid SHS to prevent chronic obstructive pulmonary disease onset. This needs to be coupled with encouragement to quit smoking, especially for heavy smokers.
Keywords: body composition; lifestyle; respiratory function; secondhand smoke; workers.