Table 3.
Multivariable-adjusted hazard ratios and 95% confidence intervals of prostate cancer risk by quintile of baseline serum α-tocopherol concentration, stratified by study population characteristics, among 29,102 Finnish male smokers in the ATBC Study
| Baseline serum α-tocopherol quintiles, range | ||||||||
|---|---|---|---|---|---|---|---|---|
| Stratified characteristics | Events | Q1 ≤ 9.3 mg/L | Q2 > 9.3 and ≤ 10.8 mg/L | Q3 > 10.8 and ≤ 12.2 mg/L | Q4 > 12.2 and ≤ 14.2 mg/L | Q5 > 14.2 mg/L | Ptrendb | Pinteractionc |
| HR (95% CI) a | ||||||||
| Age at randomization, y | 0.28 | |||||||
| <55 | 972 | 1.00 (Ref) | 0.89 (0.72, 1.11) | 1.01 (0.81, 1.25) | 0.97 (0.77, 1.22) | 0.91 (0.70, 1.17) | 0.99 | |
| 55–59 | 877 | 1.00 (Ref) | 1.17 (0.93, 1.47) | 1.17 (0.93, 1.47) | 1.09 (0.86 1.39) | 0.96 (0.73 1.26) | 0.17 | |
| ≥60 | 875 | 1.00 (Ref) | 0.80 (0.65, 0.98) | 0.83 (0.66, 1.03) | 0.86 (0.68, 1.07) | 0.78 (0.61, 1.01) | 0.71 | |
| Years of smoking | 0.67 | |||||||
| <32 | 831 | 1.00 (Ref) | 0.96 (0.76, 1.22) | 1.15 (0.91, 1.46) | 1.05 (0.82, 1.35) | 1.01 (0.76, 1.34) | 0.87 | |
| 32–39 | 910 | 1.00 (Ref) | 1.05 (0.84, 1.31) | 1.01 (0.81, 1.27) | 1.02 (0.80, 1.29) | 0.86 (0.66, 1.12) | 0.31 | |
| ≥40 | 983 | 1.00 (Ref) | 0.84 (0.70, 1.03) | 0.87 (0.71, 1.07) | 0.88 (0.71, 1.09) | 0.81 (0.64, 1.04) | 0.99 | |
| Number of cigarettes smoked daily | 0.69 | |||||||
| <20 | 1 121 | 1.00 (Ref) | 0.96 (0.79, 1.18) | 0.94 (0.76, 1.15) | 0.98 (0.80, 1.21) | 0.84 (0.66, 1.06) | 0.62 | |
| ≥20 | 1 603 | 1.00 (Ref) | 0.91 (0.78, 1.07) | 1.02 (0.87, 1.20) | 0.94 (0.79, 1.12) | 0.90 (0.74, 1.10) | 0.61 | |
| BMI (range), kg/m2 | 0.83 | |||||||
| <24.5 | 857 | 1.00 (Ref) | 0.92 (0.75, 1.13) | 1.05 (0.85, 1.31) | 0.94 (0.74, 1.19) | 0.92 (0.69, 1.22) | 0.88 | |
| 24.5–27.6 | 981 | 1.00 (Ref) | 0.89 (0.72, 1.10) | 0.87 (0.70, 1.08) | 0.94 (0.75, 1.17) | 0.75 (0.58, 0.97) | 0.93 | |
| ≥27.6 | 884 | 1.00 (Ref) | 1.00 (0.80, 1.26) | 1.07 (0.85, 1.35) | 1.00 (0.79, 1.26) | 0.98 (0.76, 1.26) | 0.36 | |
| α-Tocopherol supplementation | 0.40 | |||||||
| Yes | 1 317 | 1.00 (Ref) | 0.95 (0.79, 1.13) | 0.98 (0.81, 1.18) | 1.00 (0.82, 1.21) | 0.79 (0.64, 0.99) | 0.69 | |
| No | 1 407 | 1.00 (Ref) | 0.93 (0.78, 1.10) | 1.00 (0.84, 1.19) | 0.93 (0.77, 1.12) | 0.96 (0.78, 1.19) | 0.71 | |
| β-Carotene supplementation | 0.49 | |||||||
| Yes | 1 379 | 1.00 (Ref) | 0.95 (0.80, 1.13) | 0.97 (0.81, 1.16) | 0.97 (0.81, 1.17) | 0.83 (0.67, 1.03) | 0.37 | |
| No | 1 345 | 1.00 (Ref) | 0.92 (0.77, 1.10) | 1.01 (0.85, 1.21) | 0.95 (0.79, 1.15) | 0.92 (0.74, 1.14) | 0.92 | |
| History of diabetes | 0.10 | |||||||
| Yes | 71 | 1.00 (Ref) | 0.60 (0.27, 1.32) | 0.38 (0.16, 0.90) | 0.76 (0.35, 1.66) | 0.61 (0.28 1.34) | 0.63 | |
| No | 2 653 | 1.00 (Ref) | 0.95 (0.83, 1.07) | 1.01 (0.89, 1.15) | 0.97 (0.85, 1.11) | 0.89 (0.76, 1.03) | 0.64 | |
Cox proportional hazards regression using person-years as the time metric to calculate hazard ratios and 95% confidence intervals of associations between measures of serum α-tocopherol (quintiles) and incidence of prostate cancer, and adjusted for age at randomization, body mass index, years of cigarette smoking, number of cigarettes smoked daily, serum total cholesterol concentration, and trial intervention group
Two-sided Ptrend is based on the statistical significance of the coefficient of the quintile variable (median value within each quintile).
Two-sided Pinteraction is based on the statistical significance of the cross-product term added to multivariable models.
Abbreviations: HR, Hazard Ratio; 95%CI, 95 % confidence interval; Ref, Referent; Q, quintile; ATBC, Alpha-Tocopherol, Beta-Carotene Cancer Prevention