Circulating C-reactive protein level is negatively correlated with lung volume

Background: We previously reported that low lung volume is associated with an increased risk for prediabetes in healthy Japanese men. Systemic inflammation is a risk factor for diabetes, and is postulated to be associated with pulmonary dysfunction. However, its scientific information is limited. Aim: The aim of this study was to investigate the association between pulmonary function and systemic inflammation. Methods: This study included 1803 middle aged (40-60 years old) apparently healthy Japanese who had received regular health checkups. All subjects underwent chest radiogram, spirometry, and blood sampling. Subjects with abnormal pulmonary function (i.e. FEV1/FVC<70% or %predicted VC<80%) were excluded. To avoid the influences of smoking, current or former smokers were excluded. We reviewed their clinical data, and evaluated associations between pulmonary function and the other parameters. Results: The serum high sensitivity CRP (hsCRP) level positively correlated with body mass index (BMI), abdominal circumference (AC), triglyceride, LDL cholesterol, and HbA1c (p<0.01 for each). The serum hsCRP level did not correlate with FEV1/FVC (p=0.23), whereas it significantly negatively correlated with %predicted VC (p<0.01). In addition, a better association between hsCRP and %predicted VC was observed in male (r=-0.18, p<0.01) than in female (r=-0.09, p=0.055). Multivariate analyses demonstrated that %predicted VC, BMI, and AC were the independent determinants for hsCRP. Conclusions: Low lung volume is associated with serum CRP level. Although systemic inflammation could be induced by various factors, it might have a close relationship with subclinical pulmonary dysfunction.