Table 2.
Final multivariable logistic regression models of the association of use of levothyroxine with colorectal cancer risk in the Molecular Epidemiology of Colorectal Cancer study in Israel*
| Variable | All participants (conditional) (n = 4008) | P | All participants (unconditional) (n = 4617) | P | Men (unconditional) (n = 2340) | P | Women (peri/postmenopausal) (unconditional) (n = 1982) | P |
| OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |||||
| Levothyroxine use, ≥5 y | ||||||||
| No | 1.00 (referent) | .001 | 1.00 (referent) | .001 | † | 1.00 (referent) | .008 | |
| Yes | 0.59 (0.43 to 0.82) | 0.60 (0.44 to 0.81) | 0.60 (0.41 to 0.87) | |||||
| Aspirin use, daily, ≥3 y | ||||||||
| No | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 |
| Yes | 0.58 (0.49 to 0.69) | 0.57 (0.49 to 0.67) | 0.57 (0.46 to 0.70) | 0.57 (0.44 to 0.75)‡ | ||||
| Statins use, ≥5 y | ||||||||
| No | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | .01 | 1.00 (referent) | <.001 |
| Yes | 0.61 (0.49 to 0.77) | 0.62 (0.50 to 0.77) | 0.70 (0.52 to 0.93) | 0.53 (0.38 to 0.74) | ||||
| HRT use ever | ||||||||
| No | NR | NR | NR | 1.00 (referent) | <.001 | |||
| Yes | 0.60 (0.43 to 0.84)‡ | |||||||
| Family history of CRC, first-degree relatives | ||||||||
| No | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | .005 | 1.00 (referent) | <.001 |
| Yes | 1.56 (1.26 to 1.94) | 1.57 (1.29 to 1.92) | 1.50 (1.13 to 2.00) | 1.75 (1.30 to 2.36) | ||||
| Sports activity | ||||||||
| No | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 |
| Yes | 0.60 (0.52 to 0.69) | 0.62 (0.55 to 0.71) | 0.68 (0.57 to 0.80) | 0.57 (0.46 to 0.70) | ||||
| Vegetables, ≥5 servings/d | ||||||||
| No | 1.00 (referent) | .003 | 1.00 (referent) | .001 | 1.00 (referent) | .001 | † | |
| Yes | 0.81 (0.71 to 0.93) | 0.81 (0.71 to 0.91) | 0.75 (0.63 to 0.89) | |||||
| Age, per year | NR | 0.99 (0.99 to 1.00) | .003 | 0.99 (0.98 to 1.00) | .03 | 0.99 (0.98 to 0.99) | <.001 | |
| Sex | ||||||||
| Men | NR | 1.00 (referent) | .003 | NR | NR | |||
| Women | 0.84 (0.74 to 0.94) | |||||||
| HRT × aspirin | NR | NR | NR | 2.72 (1.12 to 6.58) | .026 | |||
*
Odds ratios shown for variables in final models only. CI = confidence interval; CRC = colorectal cancer; HRT = hormone replacement therapy; NR = not relevant; OR = odds ratio.
†
Dropped out of final model.
‡
This model includes an interaction of HRT × aspirin; therefore, the aspirin effect is among non-HRT users and the HRT effect is among non-aspirin users.