Table 4. Association between sleep duration and risk of colorectal cancer by use of HRT in the WHI-OS (1994–2010).
| HRT | Never ( n =24 681) | Ever ( n =48 986) | |||||
|---|---|---|---|---|---|---|---|
| Sleep duration (hours per night) | Cases a | HR b | 95% CI | Cases a | HR b | 95% CI | P -value c |
| ⩽5 | 41 | 1.75 | 1.23, 2.50 | 40 | 1.07 | 0.78, 1.50 | |
| 6 | 88 | 1.12 | 0.86, 1.45 | 134 | 1.01 | 0.82, 1.24 | |
| 7–8 | 174 | 1.00 | 305 | 1.00 | |||
| ⩾9 | 13 | 1.00 | 0.57, 1.76 | 40 | 1.70 | 1.22, 2.37 | 0.03 |
Abbreviation: cases=number of incident case; CI=confidence interval; HR=hazard ratio; HRT=hormone replacement therapy; WHI-OS=Women’s Health Initiative–Observational Study.
a
The analysis was based on 73 667 women who reported the use of HRT.
b
HR was adjusted for age, ethnicity, fatigue, waist to hip ratio, and physical activity.
c
P-value for interaction.