Table 2.
Mean Sleep Parameters (95% Confidence Interval) by Level of Depressive Symptoms*
| Parameter of Sleep Quality | 0–2
(Normal) (n = 2310) |
3–5
(Some Depressive Symptoms) (n = 537) |
≥6
(Depressed) (n = 204) |
P for trend |
|---|---|---|---|---|
| Objective Sleep Parameters | ||||
| Sleep Efficiency, %† | 83.5 (83.1–83.8) | 81.5 (80.7–82.3) | 81.2 (79.8–82.4) | <.001 |
| Sleep Latency, minutes† | 21.3 (20.6–22.0) | 23.7 (22.2–25.4) | 26.7 (24.0–29.8) | <.001 |
| Awake After Sleep Onset, minutes† | 65.1 (63.6–66.6) | 74.1 (70.7–77.7) | 77.1 (71.4–83.3) | <.001 |
| Number of Long Wake Episodes | 6.7 (6.6–6.8) | 7.4 (7.1–7.7) | 7.7 (7.3–8.2) | <.001 |
| Total Sleep Time, hours | 6.4 (6.4–6.5) | 6.3 (6.2–6.4) | 6.4 (6.2–6.6) | 0.226 |
| Subjective Sleep Parameters | ||||
| Pittsburgh Sleep Quality Index (0–21) | 5.1 (5.0–5.2) | 6.9 (6.6–7.1) | 8.6 (8.2–9.0) | <.001 |
| Epworth Sleepiness Scale (0–24) | 5.8 (5.7–6.0) | 6.9 (6.6–7.2) | 8.0 (7.5–8.5) | <.001 |
*
Adjusted for age and site
†
Transformed for normality using log(100−P+1) for sleep efficiency and log(P+1) for sleep latency and wake after sleep onset; results back-transformed for interpretation