Relationship of body composition and C-reactive protein with pulmonary function

Objectives: It has been observed that restrictive pulmonary function is associated with obesity and C-reactive protein (CRP), an indicator for systemic inflammation. However, the interrelationship among body composition, CRP, and restrictive pulmonary function has been poorly understood. This study focused on the combined effects of body composition and CRP on restrictive pulmonary function. Methods: We performed a cross-sectional study to examine the association of body composition and CRP with restrictive pulmonary function in 12,787 subjects (7083 men, 5704 women; ages 20-75 yr). We evaluated body composition and CRP as a categorical variable (non-obesity, percentage body fat ≤75 percentile; obesity, percentage body fat >75 percentile; low-inflammation, CRP ≤75 percentile; high-inflammation, CRP >75 percentile) and constructed 4 groups, which were non-overlapping (reference, inflammatory, obese, obese and inflammatory). The odds ratios (ORs) and 95% confidence intervals (CIs) for restrictive pulmonary function were calculated across all 4 groups. Results: The adjusted ORs (95% CIs) for restrictive pulmonary function according to the 4 groups were 1.00(reference), 1.19(0.93-1.52), 2.01(1.53-2.64) and 3.51(2.60-4.74) in men and 1.00 (reference), 1.26 (0.96-1.69), 1.02 (0.58-1.81), and 3.32 (2.09-5.27) in women after adjusting for confounding variables. Interaction was found between the body fat percentage and CRP in women only (P < 0.05). Conclusions: In summary, the coexistence of high fat accumulation and systemic subclinical inflammation is associated with restrictive pulmonary function.