Abstract
BackgroundSecondary polycythemia is associated with cigarette smoking and chronic obstructive pulmonary disease (COPD). However, the prevalence of polycythemia in COPD and the contributing risk factors for polycythemia in COPD have not been extensively studied.MethodsWe analyzed the presence of secondary polycythemia in current and former smokers with moderate to very severe COPD at the five-year follow-up visit in the observational COPDGene study. We used logistic regression to evaluate the association of polycythemia with age, sex, race, altitude, current smoking status, spirometry, diffusing capacity for carbon monoxide (DLCO), quantitative chest CT measurements (including emphysema, airway wall thickness, and pulmonary artery to aorta diameter ratio), resting hypoxemia, exercise-induced hypoxemia, and long-term oxygen therapy.ResultsIn a total of 1928 COPDGene participants with moderate to very severe COPD, secondary polycythemia was found in 97 (9.2%) male and 31 (3.5%) female participants. In a multivariable logistic model, severe resting hypoxemia (OR 3.50, 95% CI 1.41–8.66), impaired DLCO (OR 1.28 for each 10-percent decrease in DLCO % predicted, CI 1.09–1.49), male sex (OR 3.60, CI 2.20–5.90), non-Hispanic white race (OR 3.33, CI 1.71–6.50), current smoking (OR 2.55, CI 1.49–4.38), and enrollment in the Denver clinical center (OR 4.42, CI 2.38–8.21) were associated with higher risk for polycythemia. In addition, continuous (OR 0.13, CI 0.05–0.35) and nocturnal (OR 0.46, CI 0.21–0.97) supplemental oxygen were associated with lower risk for polycythemia. Results were similar after excluding participants with anemia and participants enrolled at the Denver clinical center.ConclusionsIn a large cohort of individuals with moderate to very severe COPD, male sex, current smoking, enrollment at the Denver clinical center, impaired DLCO, and severe hypoxemia were associated with increased risk for secondary polycythemia. Continuous or nocturnal supplemental oxygen use were associated with decreased risk for polycythemia.
Highlights
Secondary polycythemia is associated with cigarette smoking and chronic obstructive pulmonary disease (COPD)
Sample characteristics Among 6284 former or current smokers with 10 packyears or greater of tobacco consumption from the COPDGene study 5-year follow-up, 1928 participants (1054 males and 874 females) with moderate to very severe COPD and available hemoglobin and hematocrit data were included in this study
The present study describes an independent association between impaired DLCO and increased risk for polycythemia, though the underlying mechanism accounting for this association remains unknown
Summary
Secondary polycythemia is associated with cigarette smoking and chronic obstructive pulmonary disease (COPD). Cigarette smoking and chronic obstructive pulmonary disease (COPD) are associated with secondary polycythemia [1, 2], which may contribute to pulmonary hypertension (PH) [3, 4], venous thromboembolism [5,6,7], and mortality in COPD [8,9,10,11]. Polycythemia in COPD has been noted to be less frequent following the widespread use of LTOT [14], yet a secular trend in polycythemia prevalence has not been well-established due to a lack of comparable samples of COPD patients across the full spectrum of disease severity. The prevalence of secondary polycythemia is unclear in a contemporary COPD population due to the recent change in the definition of polycythemia and an increased use of LTOT in COPD patients
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