Systemic inflammation and decline in lung function in a general population: a prospective study

Background: An increase in levels of C- reactive protein ( CRP), a marker of systemic inflammation, is associated with reduced forced expiratory volume in 1 s ( FEV1), supporting the hypothesis that the pathophysiology of chronic obstructive pulmonary disease has a systemic inflammatory component. However, few large studies have assessed the relationship between systemic inflammation as measured by CRP and decline in lung function prospectively in a randomly selected population. Methods: In 1991, data were collected on FEV1 and forced vital capacity ( FVC) and a blood sample was taken from 2442 randomly selected adults in a community- based cohort. In 2000 these measures were repeated in 1301 individuals. The level of serum CRP was analysed in these samples from 1991 and 2000. Results: In cross-sectional analyses of data from 1991 and 2000, serum CRP levels were inversely related to FEV1 and FVC. After adjustment for smoking and other confounders, the difference in FEV1 was reduced by -9 ml ( 95% CI - 13 to - 5) and - 7 ml ( 95% CI - 13 to - 2) for each mg/I increment in serum CRP in 1991 and 2000, respectively. There was no significant association between baseline serum CRP levels and decline in FEV1 and FVC over 9 years. Conclusions: Although serum CRP levels are inversely associated with lung function in cross-sectional studies, there was no effect of a marker of systemic inflammation on decline in lung function over 9 years.