Respiratory risk factors and mortality: longitudinal studies in Washington County, Maryland

Risk factors for temporal changes in chronic respiratory disease mortality were evaluated from two studies conducted in Washington County, Maryland. The first examined the mortality of a private census population (greater than 35,000 whites) enumerated in 1963 over two subsequent time periods by age, sex, and initial smoking status. The second examined the 10-yr mortality of a subset of the 1963 census (884 men who had undergone spirometry). We observed a fall in age-adjusted mortality from all causes and from arteriosclerotic heart disease (ASHD), but an increase in COPD mortality. However, the increase in these chronic pulmonary deaths is essentially confined to persons who were smoking cigarettes at the beginning of the study period. Furthermore, while smokers showed an increased mortality risk for all causes, the excess mortality risk did not fall uniformly across cigarette smokers. It is a major observation of this study that all-cause and cardiovascular (as well as pulmonary) mortality are significantly more often found among subjects with ventilatory impairment (independent of smoking status). Reasons for the association of ASHD mortality with impaired forced expiration are discussed. Thus, men at increased risk for three (ASHD, lung cancer, COPD) of the five leading causes of death (three of eight for women) may be identified by spirometry. Perhaps it is time that this test was more generally applied.