Table 2.
Demographics and descriptive statistics of sleep and alertness
| No. participants | 833 |
| Age | 46.20 ± 11.93 yrs |
| Sex | 233 M/600 F |
| BMI | 25.83 ± 5.12 kg/m2 |
| PSQI | 4.86 ± 2.73 |
| Race | 747 White/33 Other or Mixed/16 Asian/7 Black |
| Twin status | 359 NT/340 MZ/134 DZ |
| Country | 749 UK/84 US |
| No. nights (total) | 9,542 |
| No. nights per Ss (grandmean) | 11.45 ± 1.77 |
| Sleep duration (grandmean) | 7.66 ± 0.80 hr |
| Sleep efficiency (grandmean) | 89.19 ± 4.22 % |
| Sleep onset (grandmean) | 23h25 ± 0h57 |
| Sleep offset (grandmean) | 07h05 ± 0h56 |
| No. alertness ratings | 89,535 |
| No. alertness ratings per day (grandmean) | 7.94 ± 2.23 |
| No. alertness ratings in the first three hours after breakfast (“morning”) | 24,002 |
| Alertness (all) | 64.14 ± 20.25 |
| Alertness (grandmean) | 63.85 ± 13.22 |
Values represent mean ± standard deviation, or counts for sex, race, twin status and country. The grandmean is the average of the individual’s average across the 14 days of the study. Source data are provided as a Source Data file.
BMI body mass index, PSQI Pittsburgh Sleep Quality Index, NT non-twin, MZ monozygotic, DZ dizygotic, Ss subject.