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