Table 2.
Night-shift work duration and colorectal cancer risk according to tumor IRS1 and IRS2 expression status in the Nurses’ Health Study
| Night-shift work duration |
|||||
|---|---|---|---|---|---|
| Never | 1 - 14 years | ≥ 15 years | Ptrend* | Pheterogeneity¶ | |
| Total colorectal cancer in the full cohorts | |||||
| No. cases (N = 1,397) | 536 | 718 | 143 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 1.01 (0.90 to 1.13) | 1.28 (1.06 to 1.54) | 0.008 | |
| Multivariable HR (95% CI)§ | 1 (ref) | 1.01 (0.90 to 1.13) | 1.20 (0.99 to 1.45) | 0.06 | |
| Total colorectal cancer among women with IRS1 data | |||||
| No. cases (N = 304) | 122 | 146 | 36 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 0.91 (0.71 to 1.16) | 1.42 (0.97 to 2.06) | 0.05 | |
| Multivariable HR (95% CI)§ | 1 (ref) | 0.90 (0.70 to 1.14) | 1.31 (0.89 to 1.91) | 0.13 | |
| IRS1 | |||||
| Negative / weak | |||||
| No. cases (N = 218) | 90 | 105 | 23 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 0.88 (0.66 to 1.17) | 1.23 (0.77 to 1.94) | 0.36 | 0.02 |
| Multivariable HR (95% CI)§ | 1 (ref) | 0.87 (0.65 to 1.15) | 1.13 (0.71 to 1.80) | 0.56 | 0.02 |
| Moderate / intense | |||||
| No. cases (N = 86) | 32 | 41 | 13 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 0.98 (0.62 to 1.56) | 1.96 (1.02 to 3.77) | 0.03 | |
| Multivariable HR (95% CI)§ | 1 (ref) | 0.97 (0.61 to 1.54) | 1.81 (0.94 to 3.48) | 0.06 | |
| Total colorectal cancer among women with IRS2 data | |||||
| No. cases (N = 308) | 119 | 153 | 36 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 0.98 (0.77 to 1.25) | 1.46 (1.00 to 2.13) | 0.04 | |
| Multivariable HR (95% CI)§ | 1 (ref) | 0.97 (0.76 to 1.23) | 1.35 (0.92 to 1.97) | 0.11 | |
| IRS2 | |||||
| Negative / weak | |||||
| No. cases (N = 206) | 90 | 98 | 18 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 0.83 (0.62 to 1.11) | 0.98 (0.59 to 1.63) | 0.95 | 0.008 |
| Multivariable HR (95% CI)§ | 1 (ref) | 0.83 (0.62 to 1.10) | 0.90 (0.54 to 1.51) | 0.72 | 0.008 |
| Moderate / intense | |||||
| No. cases (N = 102) | 29 | 55 | 18 | ||
| Age-adjusted HR (95% CI) | 1 (ref) | 1.46 (0.93 to 2.29) | 2.92 (1.61 to 5.30) | 0.0004 | |
| Multivariable HR (95% CI)§ | 1 (ref) | 1.42 (0.90 to 2.22) | 2.69 (1.48 to 4.89) | 0.001 | |
CI, confidence interval; HR, hazard ratio.
Duplication-method Cox proportional cause-specific hazards regression for competing risks data was used to compute HRs and 95% CIs.
All analyses were stratified by age (in month) and year of questionnaire return.
Linear trend test using the median years of each category.
The likelihood ratio test was used to test for the heterogeneity of the associations between night-shift work duration (median) and colorectal cancer risk according to the expression of IRS1 and IRS2 (ordinal).
Multivariable hazard ratios were adjusted for age (in month), adult BMI (< 25, 25 -< 27.5, 27.5 -< 30, or ≥ 30 kg/m2), smoking (0, 1-10, or > 10 pack-years), history of colorectal cancer in a parent or sibling (yes or no), history of sigmoidoscopy/colonoscopy (yes or no), postmenopausal status and hormone use (premenopause, postmenopause and never use hormone, postmenopause and current use hormone, postmenopause and past use hormone), physical activity (< 3, 3 -< 27, ≥ 27 METS - hours/week), regular aspirin use (yes or no), alcohol consumption (0 -< 5, 5 -< 15, or ≥ 15 g/day), total intake of vitamin D, folate, calcium, red meat and processed meat (all in tertiles), sleep duration (< 6h, 6 -< 7h, 7 -< 8h, 8 -< 9h, or ≥ 9h), and history of type 2 diabetes (yes or no).