Table 2

HRs (95% CI) for type 2 diabetes risk among 39 071 adult women in the Sister Study, with women with poor sleep compared with women with recommended sleep

T2DM incidence rateModel IModel IIModel IIIModel IVModel V
Per 1000
person-years
HR (95% CIs)HR (95% CIs)HR (95% CIs)HR (95% CIs)HR (95% CIs)
Sleep duration*
 Short sleep versus6.6 1.34 (1.22 to 1.48) 1.13 (1.02 to 1.26)1.11 (1.00 to 1.23)1.03 (0.93 to 1.14)1.09 (0.98 to 1.21)
 Recommended (reference)4.9
Time to fall asleep
 >30 min versus6.9 1.36 (1.22 to 1.53) 1.18 (1.05 to 1.32) 1.14 (1.01 to 1.28)1.08 (0.96 to 1.22)1.11 (0.99 to 1.25)
 ≤30 min (reference)5.1
Frequent night awakenings
 Yes† versus6.5 1.22 (1.07 to 1.39) 1.19 (1.04 to 1.35) 1.17 (1.03 to 1.34)1.09 (0.95 to 1.24)1.14 (1.00 to 1.30)
 No (reference)5.2
Napping frequency
 ≥3 times/week versus8.4 1.65 (1.45 to 1.89) 1.50 (1.32 to 1.72) 1.36 (1.18 to 1.56) 1.19 (1.04 to 1.37) 1.30 (1.13 to 1.49)
 <3 times/week (reference)5.1
Cumulative sleep score
 1 versus5.7 1.27 (1.14 to 1.41) 1.14 (1.02 to 1.27) 1.09 (0.98 to 1.22)1.03 (0.93 to 1.15)1.08 (0.96 to 1.20)
 0 (reference)4.5
 2–4 versus7.8 1.72 (1.52 to 1.94) 1.40 (1.24 to 1.59) 1.31 (1.15 to 1.49) 1.14 (1.00 to 1.30) 1.25 (1.10 to 1.42)
 0 (reference)4.5
  • Model I: adjusted for age (years) at baseline.

  • Model II: further adjusted for race/ethnicity, educational attainment (<HS, HS/GED, some college, and ≥bachelor's degree), marital status, and status of shift work/irregular hours (yes/no).

  • Model III: further adjusted for smoking status (current, past, andnever), alcohol consumption (current, past, and never), diet (daily glycemic load), and physical activity (MET hours).

  • Model IV: further adjusted for hypertension, waist-to-hip ratio (WHR), and BMI (kg/m2) measured at baseline.

  • Model V: without WHR and BMI.

  • HRs are in bold.

  • *Long sleep duration (>9 hours) is not reported (n=356).

  • †Frequent night awakenings was classified as ‘No’ if participant reported waking up while sleeping less than three times per week and ‘Yes’ if participant reported waking up while sleeping more than three times per night/day for more than three nights/days per week.

  • ‡Cumulative sleep score was calculated by summing each participant's ‘yes’ response for each sleep characteristic. Scores range from 0 to 4, with poor sleep characteristics being combined into the category ‘2 to 4’.

  • BMI, body mass index; GED, general education diploma;HS, high school; MET, metabolic equivalent of task.