Smoking and mortality in stroke survivors: can we eliminate the paradox?

Many studies have suggested that smoking does not increase mortality in stroke survivors. Index event bias, a sample selection bias, potentially explains this paradoxical finding. Therefore, we compared all-cause, cardiovascular disease (CVD), and cancer mortality by cigarette smoking status among stroke survivors using methods to account for index event bias.

Among 5797 stroke survivors of 45 years or older who responded to the National Health Interview Survey years 1997-2004, an annual, population-based survey of community-dwelling US adults, linked to the National Death Index, we estimated all-cause, CVD, and cancer mortality by smoking status using Cox proportional regression and propensity score analysis to account for demographic, socioeconomic, and clinical factors. Mean follow-up was 4.5 years.

From 1997 to 2004, 18.7% of stroke survivors smoked. There were 1988 deaths in this stroke survivor cohort, with 50% of deaths because of CVD and 15% because of cancer. Current smokers had an increased risk of all-cause mortality (hazard ratio [HR], 1.36; 95% confidence interval [CI], 1.14-1.63) and cancer mortality (HR, 3.83; 95% CI, 2.48-5.91) compared with never smokers, after controlling for demographic, socioeconomic, and clinical factors. Current smokers had an increased risk of CVD mortality controlling for age and sex (HR, 1.29; 95% CI, 1.01-1.64), but this risk did not persist after controlling for socioeconomic and clinical factors (HR, 1.15; 95% CI, .88-1.50).

Stroke survivors who smoke have an increased risk of all-cause mortality, which is largely because of cancer mortality. Socioeconomic and clinical factors explain stroke survivors' higher risk of CVD mortality associated with smoking.