Table 2.
Multivariate regressions for time in bed, sleep duration, and sleep proportion in Norwich, United Kingdom, from 2006 to 2007.
| Time in bed (min) | P value | Sleep duration (min) | P value | Sleep proportion | P value | |
|---|---|---|---|---|---|---|
| Age (per 10-year increase) | 1.2 (−1.2 to 3.6) | .251 | −5.4 (−8.4 to −2.4)⁎⁎ | <.001 | −0.01 (−0.02 to −0.01)⁎⁎⁎ | <.001 |
| Sex | <.001 | <.001 | <.001 | |||
| Men | Reference | |||||
| Women | 9.0 (6.0–12.0)⁎⁎⁎ | −9.6 (−13.8 to −6.0)⁎⁎⁎ | −0.03 (−0.04 to −0.03)⁎⁎⁎ | |||
| Social class | .057 | .064 | .189 | |||
| Nonmanual | Reference | |||||
| Manual | −1.8 (−4.8 to 1.2) | −3.6 (−7.8 to 0.0) | 0 (−0.01 to 0.00) | |||
| Education | .022 | .010 | <.001 | |||
| Lower | Reference | |||||
| Higher | −3.6 (−6.6 to −0.6)⁎ | 4.8 (1.2–9.0)⁎⁎ | 0.01 (0.01–0.02)⁎⁎⁎ | |||
| Working status | <.001 | <.001 | <.001 | |||
| Not working | Reference | |||||
| Working ⩽35 h/w | −15.0 (−18.6 to −10.8)⁎⁎⁎ | −4.8 (−9.6 to 0.0) | 0.01 (0.00–0.02)⁎⁎ | |||
| Working >35 h/w | −32.4 (−37.8 to −27.6)⁎⁎⁎ | −20.4 (−27.0 to −13.8)⁎⁎⁎ | 0.01 (0.00–0.02)⁎ | |||
| Marital status | .004 | <.001 | .050 | |||
| Single | Reference | |||||
| Married | 10.2 (3.0–18.0)⁎⁎ | 6.6 (−3.0 to 15.6) | 0.00 (−0.02 to 0.01) | |||
| Others# | 6.0 (−1.8 to 14.4) | −3.6 (−13.8 to 6.6) | −0.01 (−0.03 to 0.00) | |||
| General health | .017 | <.001 | <.001 | |||
| Good to excellent | Reference | |||||
| Fair or poor | 4.8 (0.6–9.0)⁎ | −15.0 (−19.8 to −9.6)⁎⁎⁎ | −0.04 (−0.05 to −0.03)⁎⁎⁎ | |||
| Preexisting diseases | .035 | .130 | .008 | |||
| No | Reference | |||||
| Yes## | 4.2 (0.0–7.8)⁎ | −3.6 (−8.4 to 1.2) | −0.01 (−0.02 to −0.00)⁎⁎ | |||
| MDD | .018 | .075 | .001 | |||
| No | Reference | |||||
| Yes | 8.4 (1.2–15.0)⁎ | −7.8 (−16.8 to 0.6) | −0.03 (−0.04 to −0.01)⁎⁎⁎ | |||
| Shift work | .800 | .077 | .088 | |||
| No | Reference | |||||
| Yes | 1.8 (−11.4 to 15.0) | 15.0 (−1.8 to 32.4) | 0.03 (−0.00 to 0.06) | |||
| Coffee intake | .347 | .883 | .660 | |||
| ⩽1 cup/d | Reference | |||||
| >1 cup/d | −1.2 (−4.2 to 1.2) | 0.0 (−3.6 to 3.6) | 0.00 (−0.01 to 0.01) | |||
| Use of sleep medication | <.001 | <.001 | <.001 | |||
| Usually | Reference | |||||
| Sometimes | −1.8 (−12.0 to 8.4) | 1.8 (−10.8 to 15.0) | 0.00 (−0.02 to 0.03) | |||
| Never | −15.6 (−23.4 to −7.8)⁎⁎⁎ | 25.2 (15.0–35.4)⁎⁎⁎ | 0.07 (0.05–0.09) | |||
Abbreviations: min, minutes; h, hours; w, week; MDD, major depressive disorder; d, day.
Results are presented as β (confidence interval) in minutes. Sample sizes: time in bed N = 5055, sleep duration N = 5842, sleep proportion N = 4866. Sleep proportion = nighttime sleep duration/time in bed. Each linear regression model includes all the above factors. All variables were concurrently measured from 2006 to 2007, except for social class, education, MDD and shift work, which were defined at baseline.
⁎
P < .05.
⁎⁎
P < .01.
⁎⁎⁎
P < .001.
#
Widowed, separated, or divorced.
##
Self-reported myocardial infarction, stroke, or cancer.