Table 3.
Hazard Ratios and 95% CIs of Incident Colorectal Cancer in the PLCO Cohort, by Quartiles of Paleolithic Diet score
| Model | Paleolithic Diet score, HR (95% CI) | P for trenda | |||
|---|---|---|---|---|---|
| Quartile 1 (lowest) | Quartile 2 | Quartile 3 | Quartile 4 (highest) | ||
| Colorectal cancerb | |||||
| Cases | 200 | 148 | 179 | 167 | NA |
| Person-years | 157688 | 136768 | 193197 | 199074 | NA |
| Incidence rate (95% CI)c | 1.27 (1.10, 1.46) | 1.08 (0.92, 1.27) | 0.93 (0.8, 1.07) | 0.84 (0.72, 0.98) | NA |
| Unadjusted | 1.00 (reference) | 0.85 (0.69, 1.06) | 0.73 (0.6, 0.89) | 0.66 (0.54, 0.81) | < 0.001 |
| Model 1d | 1.00 (reference) | 0.87 (0.71, 1.08) | 0.77 (0.62, 0.94) | 0.72 (0.58, 0.90) | 0.002 |
| Model 2e | 1.00 (reference) | 0.88 (0.71, 1.09) | 0.79 (0.64, 0.97) | 0.76 (0.61, 0.95) | 0.009 |
| Proximal colon cancer | |||||
| Cases | 117 | 94 | 109 | 100 | NA |
| Incidence rate (95% CI) c | 0.74 (0.62, 0.89) | 0.69 (0.56, 0.84) | 0.56 (0.47, 0.68) | 0.50 (0.41, 0.61) | NA |
| Unadjusted | 1.00 (reference) | 0.93 (0.71, 1.21) | 0.76 (0.59, 0.99) | 0.68 (0.52, 0.88) | 0.002 |
| Model 1d | 1.00 (reference) | 0.93 (0.71, 1.22) | 0.77 (0.59, 1.00) | 0.70 (0.52, 0.92) | 0.006 |
| Model 2e | 1.00 (reference) | 0.94 (0.71, 1.23) | 0.78 (0.60, 1.02) | 0.73 (0.55, 0.97) | 0.02 |
| Distal CRC | |||||
| Cases | 82 | 54 | 69 | 67 | NA |
| Incidence rate (95% CI)c | 0.52 (0.42, 0.65) | 0.39 (0.30, 0.52) | 0.36 (0.28, 0.45) | 0.34 (0.27, 0.43) | NA |
| Unadjusted | 1.00 (reference) | 0.76 (0.54, 1.07) | 0.69 (0.50, 0.95) | 0.65 (0.47, 0.89) | 0.008 |
| Model 1d | 1.00 (reference) | 0.80 (0.57, 1.13) | 0.77 (0.55, 1.06) | 0.78 (0.55, 1.10) | 0.15 |
| Model 2e | 1.00 (reference) | 0.81 (0.58, 1.15) | 0.79 (0.57, 1.09) | 0.82 (0.58, 1.16) | 0.25 |
a: Trend test was performed using median value of each diet score quintile as a continuous variable
b: Including 420 proximal colon cancer cases, 272 distal CRC (that is, distal colon and rectal cancer) cases, and 2 CRC cases with an unknown site
c: Incidence rate was calculated per 1000 person-years
d: Model 1 was controlled with age (continuous), sex (male, female), race (white, no-white), education levels (high-school graduate or less, some college or college graduate)
e: Model 2 was additionally controlled with family history of colorectal cancer (no, yes or possibly), history of colon comorbidity (no, yes), history of diverticulitis or diverticulosis (no, yes), history of colorectal polyp (no, yes), history of diabetes (no, yes), history of aspirin use (no, yes), total energy intake (continuous), BMI at baseline (continuous), smoking status (never, current, former), and physical activity level (continuous)
HR hazard ratio, CI confidence interval, NA not applicable