Table 2.
Associations Between Sleep Duration and Subjective Sleep Quality With Risk of BC in Studied Subjects (n = 816).
| Characteristics | Total (N = 816) | Cases (n = 408) | Controls (n = 408) | P-Values* | OR (95% CI) | ||
|---|---|---|---|---|---|---|---|
| Sleep characteristics | Unadjusted | Adjusted** | |||||
| Sleep onset latency (minutes) | 815 | 40 ± 0.32 | 40 ± 0.24 | .142 | — | — | |
| Duration of sleep (hours) | 815 | 6 ± 0.07 | 7 ± 0.06 | .049* | — | — | |
| Sleeping hours | |||||||
| Sleeping hours | ≤6 h | 378 | 191 (47%) | 187 (46%) | .612 | 1.5 (.0-2.3) | 1.02 (.5-2.1) |
| 7 – 8 h | 336 | 158 (39%) | 178 (44%) | 1.3 (.7-1.8) | 1 (.6-1.6) | ||
| >8 h | 98 | 56 (14%) | 42 (10%) | Reference | Reference | ||
| Overall self-reported sleep quality | Very good | 135 | 76 (19%) | 59 (15%) | .561 | Reference | Reference |
| Good | 284 | 130 (32%) | 154 (38%) | .8 (.7-1) | .9 (.7-1.2) | ||
| Bad | 233 | 114 (28%) | 119 (29%) | .9 (.8-1.2) | 1 ( .8-1.3) | ||
| Very bad | 161 | 74 (18%) | 87 (21%) | .8 (.7-1) | .9 (.7-1.2) | ||
*At α = .05, Student t tests or chi-square tests were used to compare group differences, ** adjusted with, age at fist menarche, age at first pregnancy, menopause status, WHR, family history of BC, breast-feeding practices stress level (high), sleep duration (>8 h).