Table 3.
Differences in the Ischemic Stroke Rate and Relative Risk in Relation to Sleep Duration in WHI-OS, 1994–2005
| Hours of sleep per night |
||||||
|---|---|---|---|---|---|---|
| ≤5 | 6 | 7 | 8 | 9 | ≥ 10 | |
| N | 7738 | 25077 | 34902 | 21158 | 3758 | 542 |
| Average length of follow-up (years) | 7.3 | 7.5 | 7.6 | 7.6 | 7.5 | 7.1 |
| Number of ischemic stroke | 99 | 325 | 372 | 286 | 69 | 15 |
| Event rate (cases/105 person-years) | 175 | 173 | 141 | 179 | 246 | 391 |
| Hazard Ratios or Relative Risks (95% confidence interval) | ||||||
| Crude analysis | 1.24 (1.08, 1.42) | 1.00 | 1.27 (1.09, 1.48) | 1.88 (1.49, 2.39) | ||
| Adjusted analyses | ||||||
| *Model-I | 1.19 (1.03, 1.37) | 1.00 | 1.23 (1.05, 1.43) | 1.74 (1.38, 2.21) | ||
| †Model-II | 1.15 (0.99, 1.34) | 1.00 | 1.24 (1.05, 1.47) | 1.66 (1.29, 2.14) | ||
| ‡Model-III | 1.16 (1.00, 1.36) | 1.00 | 1.26 (1.07, 1.49) | 1.71 (1.33, 2.21) | ||
| §Model-IV | 1.14 (0.97, 1.33) | 1.00 | 1.24 (1.04, 1.47) | 1.70 (1.32, 2.21) | ||
*
Model-I: adjusted for age and race
†
Model-II: adjusted for Model-I covariates plus socioeconomic status (education, family income, and employment status)
‡
Model-III: adjusted Model-II covariates plus depression (5-item CES-D)
§
Model-IV: adjusted for Model-III covariates plus smoking, exercise, use of hormone therapy and relevant CVD risk factors (prior CVD, DM, hypertension, high cholesterol level requiring pills, BMI)