CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Lori B. Daniels, MD, MAS, FACC*,
Gail A. Laughlin, PhD,
Paul Clopton, MS,
Alan S. Maisel, MD, FACC and
Elizabeth Barrett-Connor, MD
* University of California, San Diego, Department of Medicine, Division of Cardiology, Mail Code 0986, 9350 Campus Point Drive, Suite 1D, La Jolla, California 92037-1300 (Email: lbdaniels{at}ucsd.edu).
We thank Dr. van Gestel and colleagues for their interest in our work (1). They wonder whether the presence of underlying chronic obstructive pulmonary disease (COPD) might have contributed to the strong association between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and outcomes in the Rancho Bernardo Study. We did not find this to be the case.
Dr. Van Gestel and colleagues stated that COPD affects nearly 35% of the elderly population; however, the article that they reference actually found this incidence only in current smokers (2). The cumulative incidence of COPD was only 14% in ex-smokers and 12% in never-smokers.
The Rancho Bernardo Study had a low prevalence of smoking, with only 4% reporting a current smoking habit. Consistent with this, the prevalence of COPD in our cohort, as determined by self-report and review of history and medications, was extremely low at only 6%. Median NT-proBNP levels did not differ based on the presence or absence of COPD (208 pg/ml vs. 171 pg/ml, p = 0.20), and adjusting for a history of COPD did not significantly influence the association of NT-proBNP with all-cause death and cardiovascular death: hazard ratios per 1-U log increase in NT-proBNP levels were 1.70 (95% confidence interval [CI]: 1.24 to 2.33, p = 0.001) versus 1.67 (95% CI: 1.21 to 2.29) for all-cause death and 1.97 (95% CI: 1.19 to 3.26, p = 0.009) versus 1.93 (95% CI: 1.17 to 3.19) for cardiovascular death in Cox proportional hazards models adjusted for age, sex, and other cardiovascular risk factors with and without COPD in the model.
Spirometry was not performed at the same Rancho Bernardo Study visit when NT-proBNP was measured, which could have led to an underestimation of the true prevalence of COPD. However, elevated natriuretic peptide levels in the setting of COPD are likely due to right ventricular dysfunction secondary to pulmonary hypertension; thus, individuals with asymptomatic COPD are unlikely to have significantly elevated levels of natriuretic peptide and would therefore be unlikely to explain a significant proportion of the association of NT-proBNP with all-cause and cardiovascular mortality (3).
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1. Daniels LB, Laughlin GA, Clopton P, Maisel AS, Barrett-Connor E. Minimally elevated cardiac troponin T and elevated N-terminal pro-B-type natriuretic peptide predict mortality in older adults: results from the Rancho Bernardo Study J Am Coll Cardiol 2008;52:450-459.[Abstract/Free Full Text]2. Pelkonen M, Notkola IL, Nissinen A, Tukiainen H, Koskela H. Thirty-year cumulative incidence of chronic bronchitis and COPD in relation to 30-year pulmonary function and 40-year mortality: a follow-up in middle-aged rural men Chest 2006;130:1129-1137. 3. Nagaya N, Nishikimi T, Okano Y, et al. Plasma brain natriuretic peptide levels increase in proportion to the extent of right ventricular dysfunction in pulmonary hypertension J Am Coll Cardiol 1998;31:202-208.[Abstract/Free Full Text]
Related Article
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Elevated N-Terminal Pro-B-Type Natriuretic Peptide Levels: The Effect of Chronic Obstructive Pulmonary Disease
- Yvette R.B.M. van Gestel, Don D. Sin, and Don Poldermans
J. Am. Coll. Cardiol. 2009 53: 458.
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