Table 1.
Baseline characteristics of the study participants according to difficulty initiating sleep categories, 1999–2004, HIPOP-OHP, Japan
| Difficulty initiating sleeping | |||
| Non | Sometimes | Often | |
| No. of subjects (%) | 3993 (61.3) | 1996 (30.7) | 520 (8.0) |
| Age * | 38.4 ± 9.5 | 38.3 ± 9.5 | 36.2 ± 9.5 |
| Gender (male, %) | 77.7 | 78.6 | 83.0 |
| BMI (kg/m2) † ‡ | 22.7 ± 0.05 | 22.7 ± 0.07 | 22.8 ± 0.14 |
| Physical activity (MET-h/week) † § | 5.5 ± 0.17 | 4.3 ± 0.24 | 5.1 ± 0.46 |
| History of hypercholesterolemia (%) | 7.5 | 7.8 | 8.4 |
| History of hypertension (%) | 11.8 | 13.1 | 13.6 |
| Smoking (%) | |||
| Never | 44.4 | 37.1 | 30.0 |
| Past | 15.9 | 12.6 | 14.1 |
| Current | 39.7 | 50.3 | 55.9 |
| Family history of diabetes (%) | 18.2 | 19.1 | 17.8 |
| Sleeping time (hours) (%) | |||
| <6 | 14.3 | 16.9 | 30.3 |
| 6–7 | 41.9 | 44.6 | 42.4 |
| 7–8 | 34.3 | 31.6 | 21.9 |
| 8< | 9.5 | 6.9 | 5.4 |
| Alcohol intake quartiles (%) | |||
| 1Q (0 mg/week) | 44.2 | 44.6 | 46.0 |
| 2Q (0.1–2.5 mg/week) | 1.4 | 1.2 | 1.0 |
| 3Q (2.6–25.0 mg/week) | 23.8 | 23.1 | 19.0 |
| 4Q (25.1-mg/week) | 22.2 | 21.0 | 24.5 |
| Data missing | 8.4 | 10.1 | 9.5 |
* Plus-minus values are means ± SD
† Plus-minus values are means ± SE
‡ BMI denotes body mass index
§ MET-h denotes metabolic equivalent hours