Relationships of Decreased Lung Function with Metabolic Syndrome and Obstructive Sleep Apnea in Japanese Males

Objective Decreased lung function as assessed by forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) is shown to be associated with cardiovascular morbidity and mortality. Although the underlying mechanisms for this association remain unknown, metabolic syndrome and obstructive sleep apnea (OSA) may have a role. We analyzed the relationships between metabolic syndrome and OSA in a cross-sectional health survey of middle-aged male employees. Methods In this secondary analysis, we re-analyzed the relationships of lung function determined by spirometry with metabolic syndrome and OSA based on the respiratory disturbance index (RDI) with a type 3 portable monitor. Results We analyzed 273 subjects. Independent of age, body mass index (BMI) and smoking, quartiles for lower FVC and FEV1 were associated with a higher risk of metabolic syndrome compared with quartiles for the highest FVC and FEV1, respectively. A similar trend was observed regarding the risk associated with waist circumference, and in FVC cases, dyslipidemia. The risk of hyperglycemia was significantly higher in quartiles for the second lowest FVC and FEV1 than in quartiles for the highest FVC and FEV1, respectively. A significant trend for an increase in RDI was observed in accordance with quartiles for lower FVC, but not FEV1. Conclusion There was a significant relationship between lung function impairment and metabolic syndrome through mainly abdominal obesity, partially through hyperglycemia, and also through dyslipidemia, but only with respect to restrictive lung function. Restrictive lung function was also related to OSA. This epidemiologic evidence may indicate underlying mechanisms between decreased lung function and cardiovascular risk.