Table 4.
Hazard ratios of proximal colon cancer, distal colon cancer, and rectal cancer by THM exposure categories in the 25 800 women in the SMC
| THMa | Non-chlorinated | Low THM (<15 µg/L) | High THM (≥ 15 µg/L) |
|---|---|---|---|
| No. of participants | 4534 | 11 376 | 9890 |
| Person-years | 77 702 | 199 926 | 173 960 |
| Proximal colon cancer | |||
| Cases | 57 | 138 | 123 |
| Age-adjusted HRb (95% CI) | 1.00 | 0.96 (0.71 to 1.31) | 0.99 (0.72 to 1.35) |
| Multivariable adjusted HRc (95% CI) | 1.00 | 0.92 (0.65 to 1.31) | 0.95 (0.66 to 1.36) |
| Distal colon cancer | |||
| Cases | 25 | 81 | 76 |
| Age-adjusted HRb (95% CI) | 1.00 | 1.27 (0.81 to 2.00) | 1.39 (0.88 to 2.18) |
| Multivariable adjusted HRc (95% CI) | 1.00 | 1.18 (0.71 to 1.96) | 1.30 (0.78 to 2.18) |
| Rectal cancer | |||
| Cases | 45 | 79 | 71 |
| Age-adjusted HRb (95% CI) | 1.00 | 0.69 (0.48 to 0.99) | 0.72 (0.49 to 1.04) |
| Multivariable adjusted HRc (95% CI) | 1.00 | 0.81 (0.53 to 1.23) | 0.85 (0.54 to 1.32) |
The sum of chloroform, bromoform, dibromochloromethane, and bromodichloromethane. CI = confidence interval; HR = hazard ratio; SMC = Swedish Mammography Cohort; THM = trihalomethane.
Adjusted for age (underlying timescale).
Further adjusted for level of education (<9, 9, 10-11, 12, and >12 years), household income (quartiles), smoking status (never, former <10, former ≥10, current <10, current ≥10 cigarettes/d), BMI (<20, 20-24.9, 25-29.9, or ≥30 kg/m2), diabetes (yes/no), physical activity (walking >40 min/d or exercise >60 min/wk, yes/no), alcohol intake (<5, 5-14.9, or ≥15 g/d), intake of red meat (quartiles), intake of processed meat (quartiles), intake of dairy products (quartiles), intake of whole grains (quartiles), total energy intake (continuous, kcal), use of calcium supplements (yes/no), drinking-water calcium (continuous, mg/L).