Smoking habits and non-Hodgkin's lymphoma : a case-control study in Northern Italy

Background. A potential relationship between non-Hodgkin′s lymphoma and tobacco smoking has been reported. This was further considered in a case-control study conducted in northern Italy in the provinces of Milan and Pordenone. Methods. A total of 429 cases of incident, histologically confirmed non-Hodgkin′s lymphoma and 1,157 controls in hospital for acute, nonneoplastic, nonimmunological, non-tobacco-related diseases were interviewed during their hospital stay. Relative risk (RR) estimates and their 95% confidence intervals (CI), according to various measures of tobacco smoking, were derived from multiple logistic regression equations including terms for age, sex, study center, body mass index, and alcohol and coffee drinking. Results. Compared with that for never smokers, the multivariate RR was 1.0 (95% Cl, 0.8 to 1.4) for both current smokers and ex-smokers. No trend in risk emerged with the number of cigarettes smoked per day (RR = 0.9, 95% Cl, 0.7 to 1.3 for less than 20 cigarettes/day, and RR = 1.2, 95% Cl, 0.8 to 1.8, for 20 or more cigarettes/day), or tar yield (RR = 1.2 for less than 17 mg, 1.0 for 17-20 mg, and 0.9 for more than 20 mg). Similarly, no trend in risk was observed with duration of smoking (RR = 1.0 for less than 30 years, 1.0 for 30-39 years, and 1.1 for 40 or more years) or age at starting smoking (RR = 1.1 for less than 20 years, 1. 0 for 20-29 years, and 1.1 for 30 years or over) and, for ex-smokers, with time since quitting (RR = 1.1 for less than 10 years and 1.0 for 10 or more years of smoking cessation). Conclusions. The present study found no association between various measures of tobacco smoking and non-Hodgkin′s lymphoma.