Table 1.
Characteristics of the study population (N=15,839).
| Factors | Total sleep duration | Deep sleep duration | Deep/total ratio | ||||
| ≤6h n=4169 | >6h n=11670 | ≤3h n=5845 | >3h n=9994 | ≤0.40 n=3309 | >0.40 n=12530 | ||
| Age, years (%) | |||||||
| 18-30 | 1.66 | 2.22a | 1.93 | 2.31a | 3.08 | 1.80a | |
| 31-40 | 13.60 | 12.28 | 11.40 | 14.73 | 14.90 | 12.03 | |
| 41-50 | 30.56 | 29.53 | 29.12 | 30.97 | 31.22 | 29.43 | |
| 51-60 | 32.14 | 31.25 | 31.90 | 30.78 | 29.65 | 31.97 | |
| >60 | 22.04 | 24.72 | 25.66 | 21.21 | 21.15 | 24.77 | |
| Sex (% female), mean (SD) | 10.75 | 14.85a | 8.96 | 16.58a | 7.89 | 15.32a | |
| Weight (kg), mean (SD) | 89.26 (19.35) | 87.33 (18.19) | 89.07 (18.93) | 87.12 (18.23) | 89.41 (19.01) | 87.42 (18.37) | |
| Heart rate (bpm), mean (SD) | 71.32 (13.97) | 70.26b (13.83) | 71.27 (14.23) | 70.12 (13.66)b | 71.26 (14.29) | 70.34 (13.76)b | |
| Steps (n/day), mean (SD) | 7237.32 (3333.24) | 7159.29 (3193.64) | 7245.94 (3231.00) | 7141.00 (3230.60) | 7146.26 (3143.14) | 7188.00 (3253.93) | |
| Diastolic blood pressure (mm Hg), mean (SD) | 77.99 (10.16) | 77.20 (9.71) | 78.14 (10.08) | 76.98 (9.67) | 78.55 (10.14) | 77.11 (9.73) | |
| Systolic blood pressure (mm Hg), mean (SD) | 126.03 (14.10) | 125.15 (13.30) | 126.08 (13.83) | 124.98 (13.31) | 126.92 (13.65) | 124.98 (13.65) | |
aChi-square and t tests were computed to compare percentages and mean values from qualitative and quantitative variables, respectively, between the low and high categories for total sleep duration, deep sleep duration and deep/total ratio.
bAll the corresponding P values were below .001 except for the heart rate variable where they were all above 0.05.