Fig. 2.

Study-specific odds ratios and 95% confidence intervals for prostate cancer per 80 percentile increase (a) in circulating folate and (b) in circulating vitamin B₁₂. The odds ratios are conditioned on the matching variables and adjusted for exact age, marital status, education level, cigarette smoking, height, and body mass index. The χ² test statistics were calculated by comparing the χ² values of models with and without the addition of a study (or study type)-times-linear trend interaction term. The 10th and 90th percentiles of folate concentration for each study (indicating the magnitude of an 80-percentile increase) are as follows: ATBC (5.4 and 13.2 nmol/l), CARET (6.5 and 42.2 nmol/l), EPIC phase 1 (4.5 and 26.9 nmol/l), EPIC phase 2 (8.0 and 33.2 nmol/l), Janus (10 and 20 nmol/l), NSHDC (3.4 and 9.4 nmol/l), and ProtecT (7.9 and 44.7 nmol/l).

ATBC = Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study; CARET = Carotene and Retinol Efficacy Trial; CI = confidence interval; EPIC = European Prospective Investigation into Cancer and Nutrition; NSHDC = Northern Sweden Health and Disease Study cohort; OR = odds ratio; ProtecT = Prostate Testing for Cancer and Treatment Trial.