We investigated the mortality pattern among subjects attending the pulmonary function laboratories associated with two academic respiratory disease clinics during the 1990s. Mortality rates among subjects diagnosed with COPD were substantially elevated, with deaths attributed to lung cancer, respiratory and circulatory causes all significantly in excess.
Among subjects with asthma, the all-causes SMR was significantly lower than expected. Despite the overall favourable survival among subjects with asthma, three deaths were attributed to asthma and two to chronic airflow obstruction, which could reflect chronic asthma.
presented the results of a multivariate analysis of risk factors for all-cause mortality using an external reference population. For subjects with COPD, after adjusting for other risk factors, women demonstrated a higher mortality risk compared with men. It is interesting that in the analysis that used an internal comparison (), women showed a lower risk than men. This may be interpreted to mean that, among subjects with COPD, the prognosis of women is better than that of men, but when compared with a largely disease-free population, women are at higher risk than men, probably due to the higher overall mortality rates of men in the general population.
As expected, cigarette smoking history and poorer lung function test results were significant predictors of increased mortality risk. The relationships between survival and the GOLD severity classification were shown in , and graphically illustrate the relationships presented in .
The comorbidities of circulatory disease and diabetes were highly prevalent among subjects with COPD, and significantly contributed to mortality risk. A study from the United Kingdom-based General Practice Research Database (15
) recently reported that the incidence of cardiovascular diseases was higher among patients diagnosed with COPD. Thus, patients with COPD need to be managed with attention devoted to both their respiratory disorders and related comorbidities. Several strategies are available. Physicians often avoid the use of β-blockers in patients with COPD and concurrent cardiovascular disease because of concerns about adverse pulmonary effects (16
). A recent observational cohort study in the Netherlands (17
) reported, however, that treatment with β-blockers may reduce the risk of exacerbations and improve survival in patients with COPD, possibly as a result of dual cardiopulmonary protective properties.
Statins are another class of medications that may prove to be of value. Young et al (18
) noted, “evidence shows statins have important anti-inflammatory effects in both the lungs and arteries. Although randomized control trials are yet to be reported, nonrandomized studies have consistently shown benefit in COPD patients taking statins compared with those not. These include reductions in both cardiovascular and respiratory morbidity/mortality”. A nonrandomized study conducted in Norway (19
), for example, reported that the HR for all-cause mortality among 854 consecutive patients discharged from hospital with a diagnosis of COPD exacerbation was 0.57 (95% CI 0.38 to 0.87) among statin users versus nonusers.
It has also been suggested that inhaled medications, in particular inhaled corticosteroids, not only reduce airway inflammation but may also reduce systemic inflammation and consequent cardiovascular sequelae (20
While these medications may provide benefit, there has been some concern that commonly prescribed treatments, such as long-acting β-agonists, may increase the risk of cardiovascular events. A recent post hoc analysis of the data set from the Towards a Revolution in COPD Health (TORCH) trial (24
) reported that the use of salmeterol did not increase the risk of cardiovascular events in patients with moderate to severe COPD.
We also explored several socioeconomic and environmental variables as risk factors for premature mortality. We found no significant association between socioeconomic status, as measured by neighbourhood income and mortality. As previously reported (11
), there was an association between residency close to traffic and increased mortality risk. In the combined analysis of the two clinics, the RR of death associated with residence close to traffic was 1.25 (95% CI 1.07 to 1.47) for subjects with COPD, and 1.61 (95% CI 0.97 to 2.68) for subjects with asthma. Efforts to reduce community air pollution levels should, thus, prove to be of benefit to subjects with respiratory disease.