Table 1.
Bivariable relationships between sleep duration and covariables in the Nurses’ Health Study I (NHS-I) at baseline year 1986, NHS-I at baseline year 2000, and Nurses’ Health Study II (NHS-II) study populations
| Self-reported sleep duration in hours per night | |||||
|---|---|---|---|---|---|
| ≤5 | 6 | 7 | 8 | ≥9 | |
| NHS-I 1986, No. (%) | 2,546 (4.2) | 15,268 (25.2) | 25,674 (42.4) | 14,408 (23.8) | 2,687 (4.4) |
| NHS-I 2000, No. (%) | 1,705 (4.9) | 8,035 (22.9) | 13,992 (39.9) | 9,111 (26.0) | 2,235 (6.4) |
| NHS-II, No. (%) | 3,689 (5.4) | 16,053 (23.3) | 29,359 (42.7) | 16,130 (23.4) | 3,553 (5.2) |
| Covariables | Mean | ||||
| Age | |||||
| NHS-I 1986 | 52.9 | 52.2 | 51.9 | 52.3 | 52.5 |
| NHS-I 2000 | 65.3 | 64.9 | 64.8 | 65.8 | 66.6 |
| NHS-II | 46.9 | 46.5 | 46.4 | 46.1 | 46.0 |
| % | |||||
| Race | |||||
| White | |||||
| NHS-I 1986 | 90.1 | 93.8 | 95.6 | 95.3 | 95.0 |
| NHS-I 2000 | 91.3 | 94.6 | 95.7 | 95.6 | 95.7 |
| NHS-II | 87.4 | 91.8 | 94.2 | 94.9 | 94.6 |
| Black | |||||
| NHS-I 1986 | 2.9 | 1.5 | 0.6 | 0.5 | 0.5 |
| NHS-I 2000 | 2.1 | 0.8 | 0.5 | 0.4 | 0.4 |
| NHS-II | 3.3 | 1.7 | 0.7 | 0.4 | 0.7 |
| Other | |||||
| NHS-I 1986 | 7.0 | 4.7 | 3.8 | 4.2 | 4.5 |
| NHS-I 2000 | 6.6 | 4.6 | 3.8 | 4.0 | 3.9 |
| NHS-II | 9.3 | 6.6 | 5.1 | 4.7 | 4.7 |
| Hispanic ethnicity | |||||
| NHS-I 1986 | 1.1 | 0.9 | 0.7 | 0.9 | 0.9 |
| NHS-I 2000 | 1.3 | 0.9 | 0.7 | 0.8 | 0.9 |
| NHS-II | 1.9 | 1.6 | 1.3 | 1.2 | 1.5 |
| Family history of hypertension | |||||
| NHS-I 1986 | 43.4 | 44.8 | 45.6 | 43.5 | 41.4 |
| NHS-I 2000 | 43.1 | 42.4 | 42.1 | 41.0 | 38.5 |
| NHS-II | 50.9 | 49.8 | 47.1 | 46.8 | 45.5 |
| Diabetes | |||||
| NHS-I 1986 | 3.1 | 2.1 | 1.7 | 2.1 | 2.8 |
| NHS-I 2000 | 4.5 | 3.8 | 3.5 | 3.7 | 5.5 |
| NHS-II | 2.5 | 1.5 | 1.3 | 1.3 | 1.9 |
| Hypercholesterolemia | |||||
| NHS-I 1986 | 10.8 | 9.3 | 8.7 | 9.8 | 9.6 |
| NHS-I 2000 | 55.0 | 52.2 | 50.6 | 52.5 | 55.5 |
| NHS-II | 32.6 | 28.0 | 25.7 | 26.3 | 31.6 |
| Body mass index ≥ 30 | |||||
| NHS-I 1986 | 14.6 | 11.6 | 8.8 | 9.1 | 11.1 |
| NHS-I 2000 | 18.2 | 15.3 | 13.1 | 12.8 | 17.6 |
| NHS-II | 24.5 | 20.4 | 16.2 | 15.7 | 19.7 |
| Snore regularly | |||||
| NHS-I 1986 | 9.4 | 8.3 | 7.4 | 8.4 | 10.5 |
| NHS-I 2000 | 15.5 | 14.1 | 13.6 | 13.8 | 16.4 |
| NHS-II | 14.8 | 13.8 | 12.9 | 12.9 | 15.3 |
| Postmenopausal | |||||
| NHS-I 1986 | 59.1 | 54.3 | 51.2 | 52.8 | 52.0 |
| NHS-I 2000 | 96.9 | 96.9 | 97.3 | 97.9 | 98.3 |
| NHS-II | 27.2 | 24.0 | 21.3 | 18.8 | 20.0 |
| Current shift worker | |||||
| NHS-I 1986 | 19.0 | 12.6 | 8.4 | 8.2 | 9.2 |
| NHS-I 2000 | 14.8 | 10.2 | 8.6 | 8.2 | 8.6 |
| NHS-II | 32.2 | 24.9 | 19.8 | 18.4 | 20.3 |
| Total activity < 9 MET hours per week a | |||||
| NHS-I 1986 | 57.0 | 54.2 | 52.4 | 53.6 | 59.0 |
| NHS-I 2000 | 42.5 | 38.3 | 36.2 | 36.7 | 44.7 |
| NHS-II | 43.3 | 39.9 | 37.3 | 37.4 | 45.5 |
| Current postmenopausal hormone therapy | |||||
| NHS-I 1986 | 19.1 | 25.0 | 27.8 | 25.9 | 25.3 |
| NHS-I 2000 | 29.3 | 26.7 | 25.3 | 25.6 | 27.6 |
| NHS-II | 18.6 | 17.6 | 16.2 | 14.1 | 16.2 |
| Current smoker | |||||
| NHS-I 1986 | 24.9 | 25.5 | 23.1 | 22.4 | 25.7 |
| NHS-I 2000 | 10.7 | 10.9 | 9.7 | 9.4 | 11.6 |
| NHS-II | 14.1 | 10.5 | 7.6 | 6.9 | 7.8 |
| Caffeine ≥ 245mg/d | |||||
| NHS-I 1986 | 45.1 | 47.6 | 46.4 | 44.1 | 40.1 |
| NHS-I 2000 | 32.4 | 35.8 | 36.6 | 36.9 | 34.8 |
| NHS-II | 30.9 | 33.8 | 33.9 | 33.3 | 31.8 |
| Alcohol > 28g/day | |||||
| NHS-I 1986 | 3.3 | 3.9 | 4.4 | 5.7 | 7.8 |
| NHS-I 2000 | 2.7 | 2.6 | 3.1 | 3.6 | 5.9 |
| NHS-II | 1.5 | 1.6 | 1.8 | 2.2 | 2.5 |
| DASH score in bottom quintile | |||||
| NHS-I 1986 | 18.1 | 16.2 | 14.8 | 14.8 | 17.6 |
| NHS-I 2000 | 16.3 | 14.1 | 11.8 | 12.6 | 13.5 |
| NHS-II | 17.8 | 15.7 | 13.5 | 13.5 | 15.6 |
| Current aspirin | |||||
| NHS-I 1986 | 60.5 | 65.8 | 67.6 | 65.7 | 63.2 |
| NHS-I 2000 | 36.1 | 38.7 | 39.4 | 40.2 | 40.0 |
| NHS-II | 87.0 | 88.7 | 89.8 | 90.1 | 89.6 |
| Current acetaminophen | |||||
| NHS-I 1986 | 37.8 | 38.2 | 37.3 | 36.0 | 36.1 |
| NHS-I 2000 | 63.2 | 61.5 | 59.0 | 57.7 | 59.7 |
| NHS-II | 72.7 | 77.2 | 80.0 | 81.1 | 78.6 |
| Current nonaspirin NSAIDs | |||||
| NHS-I 1986 | 53.7 | 54.7 | 56.5 | 58.8 | 57.1 |
| NHS-I 2000 | 30.3 | 32.7 | 34.2 | 37.6 | 36.6 |
| NHS-II | 59.3 | 59.2 | 61.2 | 63.4 | 63.7 |
Because of large sample sizes, all of the bivariable analyses between sleep duration and the covariables were highly statistically significant. Abbreviations: DASH, Dietary Approaches to Stop Hypertension; MET, Metabolic Equivalent; NSAID, Non-Steroidal Anti-Inflammatory Drug.
aNine MET hours per week is equivalent to 3 hours per week of walking at a moderate pace.