Cigarette smoking and risk of non-Hodgkin's lymphoma subtypes.

We examined the hypothesis that cigarette smoking increases the risk of non-Hodgkin's lymphoma (NHL) subtypes in a cohort of approximately 253,000 members of the Kaiser Permanente Medical Care Program, ages 16-84 years, who completed a self-administered questionnaire during the period 1964-1991 that ascertained smoking history. Using information from the Surveillance, Epidemiology, and End Results cancer registry that operates in the area and the Kaiser Permanente cancer registry, we identified 674 incident cases of NHL through 1993. We observed a positive association between smoking and risk of follicular lymphoma (compared with nonsmokers: former smokers, relative risk = 1.9 with 95% confidence interval = 1.2-2.9; current smokers, relative risk = 1.4 with 95% confidence interval = 0.9-2.2), although the strength of the association did not increase consistently with increasing duration and intensity of smoking. We observed no relationship between smoking status and the risks of small cell lymphocytic, diffuse, or high-grade lymphoma, nor was smoking related to the risk of all histological types of NHL combined. These results give limited evidence for a relationship between smoking and the risk of follicular lymphoma.