Table 1.
Characteristics | Cycle 1† | Cycle 2 | Cycle 3 | Cycle 4 |
---|---|---|---|---|
Exposure period | 1985–1988 to 1991–1994 | 1991–1994 to 1997–1999 | 1997–1999 to 2002–2004 | 2002–2004 to 2007–2009 |
Outcome follow-up period | 1991–1994 to 1997–1999 | 1997–1999 to 2002–2004 | 2002–2004 to 2007–2009 | 2007–2009 to 2012–2013 |
Number of participants‡ | 5,545 | 4,117 | 3,878 | 4,238 |
Age (years), mean (SD) | 49.8 (6.0) | 55.4 (5.9) | 60.6 (5.9) | 65.2 (5.7) |
Sex (% male) | 71.2 | 71.3 | 72.7 | 73.9 |
Ethnicity (% white) | 92.0 | 93.1 | 94.0 | 94.7 |
Employment grade (% low grade) | 15.9 | 13.9 | 12.5 | 11.4 |
BMI (kg/m2), mean (SD) | 24.4 (3.2) | 25.0 (3.4) | 25.9 (3.8) | 26.2 (4.0) |
Sleep duration at beginning of exposure period (%) | ||||
≤5 h | 4.1 | 3.7 | 7.0 | 7.3 |
6 h | 27.1 | 20.6 | 33.4 | 32.3 |
7 h | 52.4 | 47.7 | 43.2 | 43.0 |
8 h | 15.6 | 25.1 | 15.0 | 15.7 |
≥9 h | 0.8 | 2.8 | 1.5 | 1.6 |
Sleep duration at end of exposure period (%) | ||||
≤5 h | 4.0 | 7.3 | 7.7 | 7.3 |
6 h | 21.0 | 32.9 | 32.3 | 29.2 |
7 h | 46.8 | 43.3 | 42.6 | 42.3 |
8 h | 25.4 | 15.0 | 15.8 | 19.4 |
≥9 h | 2.9 | 1.5 | 1.7 | 1.8 |
*Definition of diabetes uses OGTT criteria or participant record of doctor-diagnosed diabetes for cycles 1 and 2, combined OGTT and HbA1c criteria or participant record of doctor diagnosis for cycle 3, and combined fasting glucose and HbA1c criteria or participant record of doctor diagnosis for cycle 4.
†Average sleep duration and change in sleep duration over the exposure period, years 1985–1988 to 1991–1994, and incident diabetes over the outcome follow-up period, 1991–1994 to 1997–1999.
‡Number of participants in the 2-h postload glucose and HbA1c analyses differ slightly from those presented here.