Fig. 1

Dose-response relationship between tobacco smoking and the risk of non-Hodgkin lymphoma a and its major subtypes: DLBCL b and follicular c. Odds ratios and 95% confidence intervals were estimated through logistic regression spline models adjusted for gender, age, study center, years of education, and place of birth. Curves are shown for best-fitting splines according to Akaike Information Criterion. The reference category was defined as never smokers. Filled circles show knot location