Stratified analysis of pooled relative risks of VTE for smokers and heterogeneity analysisa.

ap-Values test homogeneity between strata.bLevels of adjustment in multivariate models: −, not adjusted for any confounding factors; +, adjusted for conventional confounding factors (i.e., age, sex); ++, further adjusted by potential cardiovascular risk factors (BCDHAP: B, BMI, body weight, circumference; C, cholesterol; D, diabetes; H, hypertension; A, alcohol consumption; P, physical activity. BMI, body weight or circumference was adjusted in every study).cStudies could contribute to one or both estimates depending on design of the primary studies.