Smoking and all-cause mortality among a cohort of urban transit operators

This study assesses the contribution of smoking to all-cause mortality among a primarily minority cohort of urban transit operators. Survey and medical exam data, obtained from 1,785 workers (61% African American; 9% female) who participated in the 1983-85 San Francisco MUNI Health & Safety Study, were matched against state and national death records through 2000. At baseline, approximately 45% of the workers were current smokers, 30% were former smokers, and 25% had never smoked. Covariates were demographic factors (gender, age, race/ethnicity) and alcohol use (average number of drinks per week). There were 198 deaths during the follow-up period. Kaplan Meier survival analysis indicated that the probability of survival did not differ between former and current smokers, but was significantly lower compared to never smokers (p < .001). Data were further analyzed using Cox regression with age, gender, race/ethnicity, years of smoking, and average weekly number of drinks as predictors of mortality. The results showed that years of smoking significantly contributed to morality (Hazard Ratio [HR] = 1.023; p < .001). Compared to Asian American transit operators, elevated mortality risk was observed for African American operators (HR=2.78, p < .01) and white operators (HR=2.93, p < .01). Gender and average weekly number of drinks were not significantly associated with mortality. Although rates of smoking have declined over the past two decades among blue-collar workers, elevated prevalence of former smoking will likely contribute to excess mortality among blue-collar populations.