Table 3.

Breast cancer HRs and 95% CIs among participants who consistently reported the same number of hours of sleep in 1986 and 2000

Person-yearsNo. incident cases of breast cancerAge-adjusted HR (95% CI)Multivariate HR * (95% CI)
≤5 h12,812410.98 (0.71-1.34)1.06 (0.77-1.46)
6 h93,7532951.01 (0.88-1.17)1.04 (0.90-1.20)
7 h 188,8905811.001.00
8 h99,0323731.21 (1.06-1.38)1.22 (1.07-1.39)
≥9 h11,296431.19 (0.87-1.63)1.17 (0.85-1.60)
Ptrend 0.010.05
  • * Adjusted for age, body mass index, height, history of benign breast disease, family history of breast cancer, parity and age at first birth, age at menarche, age at menopause, postmenopausal hormone use, physical activity, alcohol and caloric intake, and smoking.

  • Reference category.

  • Test for trend modeling sleep as continuous categories and calculating Wald statistic.