Relation of FEV1 and peripheral blood leukocyte count to total mortality. The Normative Aging Study

Increased peripheral blood leukocyte count and decreased level of pulmonary function have both been implicated as causes of increased total mortality in population-based studies. The extent to which these factors are independent of cigarette smoking is controversial. The authors explored the relation of leukocyte count and the level of forced expiratory volume in 1 second to total mortality in the Normative Aging Study population in the Boston, Massachusetts, area. Other covariates examined included forced vital capacity, height, body mass index, systolic and diastolic blood pressure, and total cholesterol. The sample for the current analysis consisted of 1,956 men who underwent the baseline Normative Aging Study examination during 1961-1969. Subjects ranged in age from 21 to 80 years of age at the time of entry. A total of 170 deaths occurred over the 30 years of follow-up. Statistical analysis was conducted utilizing Cox proportional hazards modeling and regression trees for censored survival data. The Cox proportional hazards model suggested that age, forced expiratory volume in 1 second, and peripheral blood leukocyte count were the three most important predictors of increased mortality in this cohort. A regression tree analysis in general confirmed these results. Both methods of analysis suggest that forced expiratory volume in 1 second and peripheral blood leukocyte count were predictors of mortality, independent of cigarette smoking.