Change in C-reactive protein levels and FEV₁ decline: A longitudinal population-based study

Summary

Reduced pulmonary function is an important predictor of cardiovascular morbidity and mortality. The mechanisms underlying this association are unknown but may involve systemic inflammation. We assessed the cross-sectional and longitudinal relationships between C-reactive protein (CRP) levels and forced expiratory volume in 1 s (FEV₁) and its decline in the general population, over a period of 8.5 years.

The analyzes were based on 531 subjects (mean age at baseline: 37±7 years, 50% women and 42% non-smokers), recruited at two French centers participating in the European Community Respiratory Health Survey. Lung function was expressed as a percentage of predicted FEV₁. CRP was measured centrally, by means of a highly sensitive assay.

In cross-sectional analysis, FEV₁ as a % of predicted values was negatively associated with serum CRP concentration ($P=0.002$). Multivariate adjustment did not alter these results ($P=0.002$). In longitudinal analysis, annual FEV₁ decline tended to increase from the lower to the upper tertile for baseline CRP concentration but the association was borderline significant ($P=0.14$). Mean values of annual FEV₁ decline were 26±32, 31±32, and 34±32 ml/year for the lower, middle and upper tertiles of baseline CRP concentration, respectively, after adjusting for potential confounders ($P=0.09$). Changes in CRP levels during follow-up were associated with annual FEV₁ decline. The mean annual FEV₁ declines in subjects with increasing CRP, in those with stable CRP and in those with decreasing CRP were 36±31, 30±31 and 24±31 ml/year, respectively ($P<0.001$). These findings were not affected by adjustment for potential confounders ($P=0.002$).

In conclusion, increases in CRP levels over time were associated with a steeper FEV₁ decline.