Association of C-Reactive Protein With Reduced Forced Vital Capacity in a Nonsmoking U.S. Population With Metabolic Syndrome and Diabetes

OBJECTIVE—A relationship between inflammation, measured by C-reactive protein (CRP), and forced vital capacity (FVC) in diabetes or metabolic syndrome (MetS) has not been established. We investigated whether high CRP is related to reduced FVC in MetS and diabetes. RESEARCH DESIGN AND METHODS—We examined the association of MetS/diabetes and CRP (normal ≤3 mg/l, high >3 mg/l) with predicted FVC in 4,272 nonsmoking U.S. adults aged 18–79 years without lung disease in the Third National Health and Nutrition Examination Survey. Logistic regression examined odds of FVC <80% by CRP and MetS/diabetes. RESULTS—Mean FVC in individuals with MetS and high CRP (95.7%) and those with diabetes and high CRP (93.7%) was lower than in those with no MetS/diabetes and normal CRP (101.7%) (P < 0.01) and was lower in those with MetS and high CRP (95.7%) than in those with MetS and normal CRP (98.5%) (P < 0.01). The odds ratio (95% CI) of FVC <80% was highest in individuals with MetS and high CRP (odds ratio 4.26 [95% CI 2.08–8.73], P < 0.01) compared with those with no MetS/diabetes and normal CRP. CONCLUSIONS—Elevated CRP is associated with lower FVC in people with MetS.