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 1983-1985 San Francisco MUNI Health and 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 < 0.001). 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 mortality (hazard ratio [HR] = 1.023; p < 0.001). Compared to Asian-American transit operators, elevated mortality risk was observed for African-American operators (HR = 2.78, p < 0.01) and white operators (HR = 2.93, p < 0.01). 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.