Fibrinogen, COPD and mortality in a nationally representative U.S. cohort

Fibrinogen is a marker of systemic inflammation and may represent an important biomarker for the progression of chronic obstructive pulmonary disease (COPD).

We used baseline data from the Third National Health and Nutrition Examination Survey (NHANES III) and follow-up mortality data to determine the relation between fibrinogen levels and COPD and to examine how fibrinogen levels at baseline affected long-term outcomes. Elevated fibrinogen was defined as the upper 10% of the fibrinogen level distribution.

Our study sample included 8,507 subjects, including 245 with Stage 3 or 4 COPD and 826 with Stage 2 COPD. Then, 3,290 of the 8,507 subjects died during the follow-up period. The mean fibrinogen level was 303.6 g/dL and 10% of the sample had levels higher than 403.0 mg/dL. Subjects with Stage 3 or 4 COPD were more likely to have a fibrinogen level > 403.0 mg/dL (odds ratio 3.4, 95% confidence interval [CI], 2.1, 5.6) than were people with normal lung function, after adjusting for covariates. An elevated fibrinogen level increased the risk of mortality (hazards ratio [HR] 1.36, 95% CI 1.13, 1.63) in the entire study sample and in subjects with Stage 3 or 4 (HR 2.11, 95% CI 1.27, 3.50) or Stage 2 (HR 1.45, 95% CI 1.08, 1.96) COPD.

In the nationally representative NHANES III data, impaired lung function is a correlate of fibrinogen levels and the presence of higher fibrinogen levels increases the risk of mortality both in the overall population and among subjects with COPD.