Table 2.
Baseline Characteristics, Overall and Stratified by Sleep Duration
| Sleep duration | p values for difference between groups | |||
|---|---|---|---|---|
| Variable | Total | <7 h/night | 7+ h/night | |
| N | 38,786 | 12,273 | 26,513 | |
| Mean age (SD) | 50.4 (15.7) | 51.4 (15.6) | 49.9 (15.7) | <0.05 |
| Women, n (%) | 24,951 (64) | 7,511 (61) | 17,440 (66) | <0.05 |
| University degree, n (%) | 11,342 (29) | 3,262 (27) | 8,080 (30) | <0.05 |
| Daytime work, n (%) | 24,103 (62) | 7,327 (60) | 16,776 (63) | <0.05 |
| Shift work, n (%) | 2,299 (5.9) | 1,028 (8.4) | 1271 (4.8) | <0.05 |
| Other work hours, n (%) | 798 (2.1) | 300 (2.4) | 498 (1.9) | <0.05 |
| No work, n (%) | 9,088 (23) | 2,794 (23) | 6,294 (24) | 0.04 |
| Sometimes depressive symptoms, n (%) | 19,686 (51) | 6,569 (54) | 13,117 (49) | <0.05 |
| Often/always depressive symptoms, n (%) | 2,450 (6.3) | 1,060 (8.6) | 1,390.(5.2) | <0.05 |
| Insomnia, n (%) | 5,283 (14) | 3,260 (27) | 2,023 (7.6) | <0.05 |
| Current smokers, n (%) | 2,869 (7.4) | 1,108 (9.0) | 1,761 (6.6) | <0.05 |
| Past smokers, n (%) | 10,185 (26) | 3,275 (27) | 6,910 (26) | 0.20 |
| BMI, kg/m2 (SD) | 24.6 (3.5) | 24.8 (3.6) | 24.5 (3.4) | <0.05 |
| Low physical activity, n (%) | 6,008 (15) | 2,010 (16) | 3,998 (15) | <0.05 |
| Coffee, no of cups/daily (SD) | 2.8 (1.8) | 3.1 (1.8) | 2.8 (1.8) | <0.05 |
| Alcohol drinkers, n (%) | 34,370 (89) | 10,942 (89) | 23,428 (88) | 0.02 |
| Standard glasses of alcohol per week (SD) | 6.4 (4.3) | 6.5 (4.4) | 6.3 (4.3) | <0.05 |
| Cancer, n (%) | 2,361 (6.1) | 773 (6.3) | 1,588 (6.0) | 0.24 |
| Cardiovascular disease, n (%) | 3,969 (10) | 1,404 (11) | 2,565 (10) | <0.05 |
Differences in baseline variables were assessed using one-way analysis of variance (ANOVA) for continuous variables and the Kruskal–Wallis test (Mann–Whitney U test) for categorical variables.