Table 1.
Associations of Actigraphy-Defined Sleep Duration. Results are Expressed as Effect Size in Minutes (95% Confidence Interval).
| Variable | N | (%) | Univariate analysis | Multivariable analysis | ||
|---|---|---|---|---|---|---|
| Female gender | 262 | (50.5) | 6.0 (−18.0, 5.9) | P = 0.32 | ||
| Younger siblings | 290 | (56.8) | 12.3 (0.3, 24.4) | P = 0.04 | 11.7 (0.3, 23.2)* | P = 0.03 |
| Older siblings | 246 | (47.5) | −4.8 (−16.8, 7.2) | P = 0.43 | ||
| Season | P <0.0001 | P <0.0001 | ||||
| Winter | 143 | (28.1) | 37.8 (21.4, 54.2) | 40.5 (24.2, 56.8)* | ||
| Spring | 147 | (28.8) | 14.0 (−2.5, 30.4) | 14.8 (1.6, 31.2)* | ||
| Summer | 95 | (18.6) | ref | ref* | ||
| Autumn | 125 | (24.5) | 27.9 (11.1, 44.8) | 31.1 (14.5, 47.7)* | ||
| Weekend night | 71 | (13.9) | −26.9 (−47.7, −6.1) | P = 0.01 | −31.5 (−51.6, −11.4)* | P = 0.002 |
| TV watching | P = 0.20 | |||||
| <1 h/day | 133 | (25.6) | 23.7 (−4.0, 52.2) | |||
| 1-3 h/day | 332 | (64.0) | 15.9 (−10.6, 42.4) | |||
| 3+ h/day | 54 | (10.4) | ref | |||
| Runs around a lot outside (parent report) | 139 | (26.8) | 7.9 (−5.3, 21.0) | P = 0.24 | ||
| Vigorous activity at least once a week (parent report) | 494 | (95.4) | 19.0 (−7.1, 45.0) | P = 0.15 | ||
| Total daytime movement counts (change in sleep duration per 105 counts)** | 519 | (100) | −3.0 (−6.0, 0.0) | P = 0.04 | −3.0 (−5.4, 0.0)† | P = 0.05 |
| Mean daytime movement counts/min (change in sleep duration per 102 counts/min)*** | 519 | (100) | 1.1 (−1.5, 3.7) | P = 0.42 | 0.9 (−1.4, 3.3)† | P = 0.44 |
| Bedtime after 21:00 | 105 | (20.2) | −49.9 (−63.7, −36.0) | P <0.0001 | −41.1 (−55.7, −26.5)† | P <0.0001 |
*
Multivariable model using season, younger siblings and weekday only.
†
Multivariable model includes each variable individually together with season, younger siblings, and weekday.
**
Mean (95% CI) total daytime movement counts 649,441 (625,908, 672,974)
***
Mean (95% CI) mean daytime movement counts/min 812 (783, 841)