Background: Reduced pulmonary function is an independent predictor of metabolic syndrome (MetS) and diabetes mellitus (DM), conditions associated with increased mortality. We investigated whether reduced pulmonary function is associated with increased mortality in persons with these conditions.
Methods: We examined 5,633 (projected, 62.4 million) US adults (age range, 18 to 79 years) in the Third National Health and Nutrition Examination Survey, who were never-smokers and were without known cardiovascular or obstructive lung disease. Cox regression (adjusted for age, sex, and ethnicity) was used to examine all-cause mortality risk across FVC categories (FVC: low, <or= 85% predicted; intermediate, 86 to 94% predicted; and high, >or= 95% predicted) among those with MetS, DM, or neither disease.
Results: The prevalence of DM and MetS significantly increased as predicted FVC decreased (p < 0.01). Age- and sex-adjusted mortality rates (per 1,000 person-years) increased in a stepwise manner as predicted FVC decreased in those patients with neither MetS nor DM (3.5 to 8.0), MetS (4.1 to 8.1), and DM (9.9 to 13.3). Compared to those with high FVC, those with low FVC had more than a fourfold increase in mortality among those with MetS (hazard ratio [HR], 4.27; 95% confidence interval [CI], 1.59 to 11.45; p < 0.01) and more than a twofold increase among those with neither disease (HR, 2.40; 95% CI, 1.06 to 5.43; p < 0.05). Also, every 10% reduction in FVC was associated with a 77% higher mortality (HR, 1.77; 95% CI, 1.33 to 2.37; p < 0.05) among persons with MetS. However, in those with DM, FVC did not contribute further to mortality risk.
Conclusion: In persons with MetS, a reduced FVC is associated with further increases in mortality, suggesting that the evaluation of lung function may be useful for risk stratification in those with MetS.