Table 3. Associations between weekly frequency of sleep disturbance and risk of colorectal cancer in the WHI-OS (1994–2010).
| 0 or <3 times | ⩾3 times | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Weekly sleep habits | Cases a | HR b | Prevalence c | Cases a | HRb,d | 95% CI | HR b , e | 95% CI | HR b , f | 95% CI | HR b , g | 95% CI |
| Use of sleeping pil | 770 | 1.00 | 10.0% | 76 | 0.98 | 0.77, 1.24 | 0.98 | 0.78-1.24 | 0.99 | 0.78, 1.26 | 0.99 | 0.78, 1.26 |
| Fall asleep during quiet activity | 618 | 1.00 | 24.3% | 223 | 1.10 | 0.95, 1.28 | 1.10 | 0.95, 1.28 | 1.07 | 0.92, 1.25 | 1.06 | 0.92, 1.24 |
| Nap in the day | 707 | 1.00 | 13.9% | 140 | 1.36 | 1.13, 1.62 | 1.14 | 0.95, 1.37 | 1.10 | 0.92, 1.33 | 1.10 | 0.91, 1.32 |
| Trouble falling asleep | 756 | 1.00 | 10.8% | 94 | 1.30 | 1.05, 1.61 | 1.25 | 1.01, 1.55 | 1.20 | 0.96, 1.50 | 1.15 | 0.91, 1.44 |
| Wake up several times | 481 | 1.00 | 40.2% | 361 | 1.18 | 1.03, 1.36 | 1.10 | 0.96, 1.27 | 1.06 | 0.92, 1.22 | 1.04 | 0.90, 1.20 |
| Wake up early than planned | 678 | 1.00 | 18.0% | 170 | 1.17 | 0.99, 1.39 | 1.15 | 0.98, 1.37 | 1.12 | 0.94, 1.33 | 1.09 | 0.91, 1.30 |
| Trouble getting back to sleep | 698 | 1.00 | 15.0% | 151 | 1.31 | 1.10, 1.56 | 1.26 | 1.06, 1.51 | 1.22 | 1.02, 1.46 | 1.19 | 0.98, 1.44 |
| Snoring | 275 | 1.00 | 16.5% | 143 | 1.20 | 0.98, 1.46 | 1.20 | 0.98, 1.47 | 1.16 | 0.95, 1.43 | 1.16 | 0.95, 1.42 |
| Poor sleep quality (very restless) | 352 | 1.00 | 2.4% | 23 | 1.39 | 0.91, 2.11 | 1.52 | 1.00, 2.32 | 1.42 | 0.93, 2.17 | 1.23 | 0.78, 1.92 |
Abbreviations: cases=number of incident cases; CI=confidence interval; HR=hazard ratio; WHI-OS=Women’s Health Initiative–Observational Study.
Two columns showed the number of cases who had less frequent sleep habit/disturbance (0 or <3 times per week) or frequent sleep habit/disturbance (⩾3 times per week), respectively. For variable ‘snoring’, many women did not report whether they snored. For variable ‘poor sleep quality’, there were 352 reported average sleep quality and 23 reported very restless sleep. The numbers in the two columns do not add up to 851 because of the missing information.
Those who reported no or less frequent experience of certain sleep habit served as the reference group, and the more frequent experience of certain habits was the comparison group.
The prevalence of the frequent experience of each sleep habit/disturbance (⩾3 times per night) in the study population.
Crude HR.
HR was adjusted for age.
HR was adjusted for age, ethnicity, fatigue, hormone replacement therapy, waist to hip ratio, and physical activity.
HR was adjusted for sleep duration in addition.