A Possible Association Between Suspected Restrictive Pattern as Assessed by Ordinary Pulmonary Function Test and the Metabolic Syndrome

Impaired restrictive pulmonary function has been reported to be associated with insulin resistance and metabolic abnormalities. However, the possible association of restrictive pulmonary defect with metabolic syndrome (MetS) is not well understood. We examined the association in comparison with C-reactive protein (CRP), which is a predictor for MetS. We recruited 2,396 apparently healthy adults and investigated the associations among pulmonary function, metabolic abnormality, and MetS, as defined by three different criteria. Abnormal pulmonary function was evaluated by both continuous pulmonary function variables including the percentage of predicted FVC (%PFVC) and a clinical category defined according to the American Thoracic Society/European Respiratory Society guidelines. CRP and %PFVC, but not FEV1/FVC ratio, were significantly correlated with metabolic abnormalities even after adjustment for confounders including waist circumference. After adjustment for age, sex, and height, the odds ratios (ORs) of a restrictive pattern (RP), as defined by a reduced FVC and a normal FEV1/FVC ratio using the lower limit of normal and RP substitutively defined by reduced FVC and an FEV1/FVC ratio of ≥ 85% for MetS, were 1.76 to 2.52 (p < 0.05 to < 0.0001) and 1.87 to 2.28 (p < 0.05 to < 0.01), respectively. The obstructive pattern (OP) was not significantly associated with any MetS criteria. A moderate-to-severe RP, but not a high CRP level (> 3.0 mg/L), was consistently associated with the three MetS criteria (OR, 2.08 to 3.57; p < 0.05 to < 0.01), even after adjustment for confounders. Impaired restrictive pulmonary function, but not OP, might be associated with metabolic disorders and MetS in a severity-dependent manner.