Table 3.
Multivariable-adjusted hazard ratios and 95% confidence intervals of lung cancer by quintile of baseline serum alpha-tocopherol concentration, stratified by age at baseline, smoking, BMI, and intervention assignment, among Finnish male smokers in the ATBC Study*
| Stratified characteristics | No. of events | Baseline serum alpha-tocopherol quintiles, range |
P trend † | P interaction ‡ | ||||
|---|---|---|---|---|---|---|---|---|
| Q1 <9.5 mg/L | Q2 9.5–10.9 mg/L | Q3 10.9–12.3 mg/L | Q4 12.3–14.2 mg/L | Q5 ≥14.2 mg/L | ||||
| HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | ||||
| Age at baseline, y | ||||||||
| <55 | 947 | 1.00 (Ref) | 0.78 (0.64 to 0.95) | 0.76 (0.62 to 0.93) | 0.62 (0.49 to 0.78) | 0.59 (0.46 to 0.75) | <.001 | .32 |
| 55–59 | 1045 | 1.00 (Ref) | 0.93 (0.77 to 1.13) | 0.88 (0.72 to 1.07) | 0.90 (0.73 to 1.11) | 0.76 (0.59 to 0.96) | .03 | |
| ≥60 | 1192 | 1.00 (Ref) | 1.02 (0.86 to 1.21) | 0.96 (0.79 to 1.15) | 0.86 (0.71 to 1.05) | 0.94 (0.76 to 1.17) | .33 | |
| Years of smoking | ||||||||
| <32 | 482 | 1.00 (Ref) | 0.77 (0.59 to 1.02) | 0.76 (0.57 to 1.004) | 0.57 (0.42 to 0.78) | 0.45 (0.31 to 0.66) | <.001 | .04 |
| 32–40 | 1069 | 1.00 (Ref) | 0.86 (0.71 to 1.04) | 0.78 (0.64 to 0.95) | 0.72 (0.59 to 0.89) | 0.65 (0.51 to 0.82) | <.001 | |
| ≥40 | 1633 | 1.00 (Ref) | 1.01 (0.87 to 1.17) | 0.96 (0.82 to 1.13) | 0.93 (0.79 to 1.11) | 0.97 (0.80 to 1.17) | .59 | |
| No. of cigarettes smoked daily | ||||||||
| <20 | 903 | 1.00 (Ref) | 0.87 (0.71 to 1.07) | 0.86 (0.70 to 1.07) | 0.80 (0.63 to 0.999) | 0.69 (0.53 to 0.90) | .006 | .17 |
| ≥20 | 2281 | 1.00 (Ref) | 0.94 (0.83 to 1.06) | 0.87 (0.76 to 1.00) | 0.80 (0.69 to 0.93) | 0.80 (0.68 to 0.94) | .002 | |
| BMI (range), kg/m2 | ||||||||
| <24.5 | 1215 | 1.00 (Ref) | 1.00 (0.85 to 1.18) | 0.99 (0.83 to 1.18) | 0.85 (0.70 to 1.04) | 0.78 (0.61 to 0.99) | .02 | .30 |
| 24.5–27.6 | 1084 | 1.00 (Ref) | 0.79 (0.65 to 0.95) | 0.74 (0.61 to 0.90) | 0.68 (0.55 to 0.83) | 0.60 (0.47 to 0.75) | <.001 | |
| ≥27.6 | 881 | 1.00 (Ref) | 0.97 (0.78 to 1.20) | 0.88 (0.70 to 1.10) | 0.89 (0.71 to 1.13) | 0.95 (0.74 to 1.21) | .70 | |
| Alpha-tocopherol supplementation | ||||||||
| Yes | 1590 | 1.00 (Ref) | 0.94 (0.80 to 1.09) | 0.88 (0.75 to 1.04) | 0.82 (0.69 to 0.98) | 0.77 (0.63 to 0.93) | .0043 | |
| No | 1594 | 1.00 (Ref) | 0.89 (0.77 to 1.04) | 0.86 (0.73 to 1.01) | 0.77 (0.65 to 0.92) | 0.75 (0.62 to 0.91) | .002 | .98 |
| β-Carotene supplementation | ||||||||
| Yes | 1612 | 1.00 (Ref) | 0.88 (0.76 to 1.03) | 0.84 (0.71 to 0.98) | 0.81 (0.68 to 0.96) | 0.77 (0.64 to 0.94) | .008 | .79 |
| No | 1572 | 1.00 (Ref) | 0.95 (0.82 to 1.11) | 0.90 (0.77 to 1.06) | 0.79 (0.66 to 0.94) | 0.75 (0.62 to 0.91) | <.001 | |
| Years of follow-up | ||||||||
| <10 | 1391 | 1.00 (Ref) | 0.91 (0.78 to 1.07) | 0.84 (0.71 to 1.00) | 0.78 (0.65 to 0.94) | 0.77 (0.63 to 0.95) | .006 | .01 |
| ≥10 | 1793 | 1.00 (Ref) | 0.94 (0.81 to 1.09) | 0.91 (0.78 to 1.06) | 0.82 (0.69 to 0.97) | 0.76 (0.63 to 0.91) | .002 | |
Cox proportional hazards regression using follow-up time as the time metric to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of associations between baseline serum alpha-tocopherol (quintiles) and incidence of lung cancer, adjusted for age at baseline, body mass index (BMI), years of cigarette smoking, number of cigarettes smoked daily, serum total cholesterol concentration, and trial intervention group. ATBC = Alpha-Tocopherol, Beta-Carotene Cancer Prevention; Q = quintile; Ref = referent.
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.