Table 4

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, stratified by race/ethnicity

Sleep characteristicsModel IInteractionModel IIInteractionModel IIIInteractionModel IVInteractionModel VInteraction
HR (95% CIs)P valueHR (95% CIs)P valueHR (95% CIs)P valueHR (95% CIs)P valueHR (95% CIs)P value
Sleep duration*
 Short sleep versus recommended (reference)0.620.510.400.320.49
 White 1.22
(1.09 to 1.37)
1.17
(1.04 to 1.32)
1.15
(1.02 to 1.30)
1.05
(0.93 to 1.19)
1.13
(1.00 to 1.27)
 Black1.09
(0.86 to 1.39)
1.01
(0.79 to 1.30)
0.96
(0.74 to 1.24)
0.95
(0.73 to 1.22)
0.95
(0.74 to 1.23)
 Hispanic/Latina1.09
(0.77 to 1.54)
1.05
(0.75 to 1.49)
1.10
(0.77 to 1.57)
1.02
(0.71 to 1.47)
1.06
(0.74 to 1.52)
Time to fall asleep
 >30 min versus ≤30 min (reference)0.190.180.240.570.45
 White 1.32
(1.15 to 1.51)
1.24
(1.09 to 1.42)
1.19
(1.04 to 1.37)
1.11
(0.97 to 1.28)
1.15
(1.00 to 1.32)
 Black1.09
(0.83 to 1.42)
1.04
(0.79 to 1.36)
1.06
(0.80 to 1.41)
1.00
(0.75 to 1.32)
1.04
(0.78 to 1.37)
 Hispanic/Latina0.96
(0.66 to 1.41)
0.94
(0.64 to 1.38)
0.86
(0.58 to 1.29)
0.90
(0.60 to 1.35)
0.89
(0.60 to 1.34)
Frequent night awakenings
 Yes† versus no (reference) 0.01 0.02 0.01 0.02 0.01
 White 1.16
(1.00 to 1.35)
1.11
(0.96 to 1.29)
1.11
(0.95 to 1.29)
1.05
(0.90 to 1.22)
1.07
(0.92 to 1.24)
 Black1.13
(0.78 to 1.63)
1.09
(0.76 to 1.58)
1.03
(0.70 to 1.51)
0.98
(0.66 to 1.44)
1.00
(0.68 to 1.48)
 Hispanic/Latina 2.18
(1.49 to 3.21)
2.19
(1.48 to 3.23)
2.19
(1.46 to 3.29)
1.97
(1.30 to 2.99)
2.21
(1.47 to 3.33)
Napping frequency
 ≥3 times/week versus <3 times/week (reference)0.600.500.550.870.68
 White 1.60
(1.37 to 1.87)
1.56
(1.34 to 1.82)
1.42
(1.21 to 1.67)
1.20
(1.02 to 1.41)
1.33
(1.14 to 1.56)
 Black 1.52
(1.11 to 2.09)
1.45
(1.05 to 2.00)
1.26
(0.89 to 1.78)
1.19
(0.84 to 1.69)
1.25
(0.89 to 1.76)
 Hispanic/Latina1.26
(0.80 to 1.99)
1.23
(0.79 to 1.95)
1.26
(0.79 to 2.02)
1.13
(0.70 to 1.81)
1.18
(0.73 to 1.89)
Cumulative sleep score0.110.070.06 0.05 0.05
White
 1 versus 0 (reference) 1.25
(1.11 to 1.41)
1.22
(1.08 to 1.38)
1.18
(1.04 to 1.33)
1.11
(0.99 to 1.25)
1.17
(1.03 to 1.32)
 2–4 versus 0 (reference) 1.55
(1.34 to 1.78)
1.43
(1.23 to 1.65)
1.35
(1.16 to 1.56)
1.15
(0.99 to 1.33)
1.25
(1.08 to 1.45)
Black
 1 versus 0 (reference)1.00
(0.74 to 1.34)
0.91
(0.68 to 1.22)
0.83
(0.61 to 1.13)
0.80
(0.59 to 1.09)
0.82
(0.60 to 1.12)
 2–4 versus 0 (reference)1.33
(0.98 to 1.79)
1.20
(0.88 to 1.62)
1.09
(0.80 to 1.50)
1.02
(0.74 to 1.41)
1.07
(0.78 to 1.47)
Hispanic/Latina
 1 versus 0 (reference)0.74
(0.49 to 1.11)
0.73
(0.48 to 1.10)
0.74
(0.48 to 1.13)
0.69
(0.44 to 1.07)
0.70
(0.46 to 1.08)
 2–4 versus 0 (reference)1.30
(0.87 to 1.95)
1.26
(0.84 to 1.88)
1.21
(0.79 to 1.85)
1.10
(0.72 to 1.70)
1.19
(0.78 to 1.82)
  • 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, and never), 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’.

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