Chest
Clinical InvestigationsCardiovascular Morbidity and Mortality in COPD
Section snippets
Source of Data
The health insurance databases of Saskatchewan were the primary source of data. The databases cover all residents eligible for health coverage, who represent approximately 99% of the population.13 Of these, approximately 91% are eligible for prescription drug benefits. These databases have been used extensively for research and provide valid information for each individual on prescriptions dispensed, hospital stay, use of physician services, and vital status.
Population
We defined a population-based cohort
Results
The population-based cohort of COPD patients comprised 5,648 subjects (53.9% male) with a mean age at cohort entry of 73.5 years (SD, 9.6 years). The mean duration of follow-up was 4.1 years (SD, 2.7 years), generating a total of 23,426 person-years (PY) of follow-up. At cohort entry, a large number of patients were being treated for some cardiovascular risk factors or had been previously hospitalized for a CVD (Table 1).
Morbidity
Overall, 22,083 hospitalizations occurred during follow-up, including 4,064 for CVD (18.4%) and 2,326 for COPD (10.5%). After subtracting the 486 PY of time spent in the hospital from the total number of PY generated by the entire cohort, 22,940 PY were at risk of hospitalization. Among women, 29.2% (n = 762) were hospitalized for CVD at least once, generating a total of 1,599 hospitalizations for CVD. Among men, a total of 2,465 hospitalizations for CVD were generated by 1,090 men (35.8%). The
Mortality
During follow-up, 2,553 deaths occurred. CVD was the underlying cause of death in 37.6% of cases (n = 960) and COPD in 14.3% (n = 364). Death rates are presented in Table 4. The overall rate of CVD death was 41.0 per 1,000 PY (95% CI, 38.4 to 43.6 PY). Among CVD, ischemic heart disease is the first cause of death across all age groups (Fig 1). It represents nearly half of all cardiovascular deaths (19.6 per 1,000 PY; 95% CI, 17.8 to 21.4 PY) and is a more frequent cause of death than COPD
Discussion
Our study shows that CVD is an important cause of death and hospitalization among patients with COPD. The rate of hospitalization for CVD was higher than that for COPD itself. CVD, more specifically ischemic heart disease, was listed more often as the underlying cause of death than was COPD. Morbidity and mortality from CVD were nearly twice as high in our cohort as in the general population.
We used a population-based cohort compiled from administrative health services databases. The use of
ACKNOWLEDGMENT
We thank Abbas Kezouh for database management and statistical advice. We also thank Caroline Quach and Mylene Kosseim for editorial comments.
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Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).
This study is based in part on nonidentifiable data provided by the Saskatchewan Department of Health. The interpretations and conclusions contained herein do not necessarily represent those of the Government of Saskatchewan or the Saskatchewan Department of Health.
This study was funded by grants from the Canadian Institutes for Health Research, AstraZeneca, Boehringer-Ingelheim, and GlaxoSmithKline. Dr. Huiart was the recipient of a research fellowship, Bourse Lavoisier, from the French Foreign Affairs Ministry. Dr. Suissa is the recipient of a Distinguished Investigator award from the Canadian Institutes for Health Research. The McGill Pharmacoepidemiology Research Unit is funded by an infrastructure grant from the Fonds de la Recherche en Santé du Québec.