Table 2.
Actigraphy Results
| Outcome | Weighted Mean (SD) |
Unadjusted Difference* |
Adjusted for Covariates† |
|||
|---|---|---|---|---|---|---|
| Caffeine (n = 94) | Placebo (n = 97) | Mean (95% CI) | P Value | Mean (95% CI) | P Value | |
| Primary outcome | ||||||
| Total sleep time (duration of sleep in sleep period), min | 488.3 (3.7) | 493.3 (3.4) | −5.1 (−15.0 to 4.9) | 0.32 | −6.7 (−15.3 to 2.0) | 0.13 |
| Secondary outcomes | ||||||
| Bedtime (clock time)§ | 21:30 (5.4) | 21:32 (4.8) | −0.02 (−0.26 to 0.22) | 0.88 | −0.05 (−0.27 to 0.17) | 0.65 |
| Time in bed (from reported bedtime to wake time), min | 614.3 (4.0) | 614.3 (3.8) | −0.1 (−10.9 to 10.8) | 0.99 | −2.1 (−11.3 to 7.2) | 0.66 |
| Sleep period (from sleep onset to sleep offset), min | 564.3 (4.1) | 566.0 (3.9) | −1.7 (−12.8 to 9.4) | 0.76 | −4.4 (−12.8 to 4.0) | 0.30 |
| Sleep efficiency (total sleep time/time in bed), % | 79.7 (0.5) | 80.5 (0.5) | −0.8 (−2.2 to 0.6) | 0.26 | −0.8 (−2.2 to 0.6) | 0.26 |
| Sleep onset latency, min | 27.4 (1.6) | 26.6 (1.6) | 0.7 (−4.0 to 5.5) | 0.76 | 1.1 (−3.6 to 5.7) | 0.65 |
| Wake after sleep onset, min | 76.0 (2.4) | 72.7 (2.3) | 3.3 (−3.1 to 9.8) | 0.31 | 2.3 (−3.9 to 8.4) | 0.48 |
| Average activity count during sleep period | 16.8 (0.7) | 16.6 (1.1) | 0.2 (−2.3 to 2.7) | 0.88 | −0.1 (−2.7 to 2.5) | 0.93 |
Definition of abbreviation: CI = confidence interval.
*
Caffeine–placebo.
†
Covariates: center, age at assessment, sex, race, maternal education, proportion of weekend nights, season.
§
SD provided in minutes. Data obtained from sleep diary.