Table 2. Meta-analysis of the association between sleep duration and cancer risk.
| Group | No. of studies (incident cases) | RR | 95%CI | P z | Statistical model | I 2 (%) | P H |
|---|---|---|---|---|---|---|---|
| Short sleep | |||||||
| All | 10 (8392) | 1.05 | 0.90-1.24 | 0.523 | Random | 57.6 | 0.012 |
| Cancer type | |||||||
| Breast cancer | 3 (4608) | 1.06 | 0.75-1.49 | 0.739 | Random | 66.3 | 0.051 |
| Colorectal cancer | 3 (2824) | 1.12 | 0.84-1.49 | 0.449 | Fixed | 55.2 | 0.107 |
| Prostate cancer | 1 (127) | 1.38 | 0.77-2.48 | 0.280 | - | - | - |
| Endometrial cancer | 1 (452) | 0.95 | 0.75-1.20 | 0.669 | - | - | - |
| Thyroid cancer | 1 (295) | 0.79 | 0.61-1.02 | 0.072 | - | - | - |
| Ovarian cancer | 1 (86) | 2.00 | 0.89-4.47 | 0.091 | - | - | - |
| Long sleep | |||||||
| All | 10 (8392) | 0.92 | 0.76-1.12 | 0.415 | Random | 68.9 | 0.001 |
| Cancer type | |||||||
| Breast cancer | 3 (4608) | 0.88 | 0.73-1.07 | 0.192 | Fixed | 15.1 | 0.308 |
| Colorectal cancer | 3 (2824) | 1.29 | 1.09-1.52 | 0.003 | Fixed | 5.8 | 0.346 |
| Prostate cancer | 1 (127) | 0.36 | 0.18-0.72 | 0.004 | - | - | - |
| Endometrial cancer | 1 (452) | 0.83 | 0.49-1.40 | 0.487 | - | - | - |
| Thyroid cancer | 1 (295) | 0.74 | 0.39-1.40 | 0.353 | - | - | - |
| Ovarian cancer | 1 (86) | 0.80 | 0.65-0.99 | 0.038 | - | - | - |
Abbreviations: OR, odds ratio; CI, confidence interval
P z, P value for Z test. P H, P value based on Q test for between-study heterogeneity