Table 2.
Correlation between PSG and actigraphy for sleep and wake parameters.
| Statistic | Wake Time (minutes) | Sleep Time (minutes) | Sleep Efficiency (%) | Sleep Latency (minutes) | Number of Awakenings |
|---|---|---|---|---|---|
| PSG | |||||
| Mean (SD) | 84.8 (60.7) | 340.2 (76.5) | 71.6 (14.5) | 38.6 (32.8) | 26.2 (14.0) |
| Actigraphy Threshold | |||||
| Low | |||||
| Mean (SD) | 79.6 (40.4) | 366.4 (73.7) | 76.8 (12.2) | 26.0 (33.9) | 32.9 (13.5) |
| Mean difference from PSG (SD)† | 5.2 (38.3) | −26.3 (56.6) | −5.1 (11.6) | 12.6 (39.6) | −6.7 (18.1) |
| Lin’s CCC (95% CI) | 0.7 (0.6–0.9) | 0.7 (0.5–0.9) | 0.6 (0.3–0.8) | 0.3 (−0.1–0.6) | 0.1 (−0.2–0.5) |
| Medium | |||||
| Mean (SD) | 57.4 (34.0) | 390.2 (70.2) | 81.5 (10.8) | 26.0 (34.0) | 30.2 (12.9) |
| Mean difference from PSG (SD) | 27.5 (41.6) | −50.0 (57.2) | −9.9 (11.5) | 12.6 (39.3) | −4.0 (18.2) |
| Lin’s CCC (95% CI) | 0.6 (0.4–0.8) | 0.6 (0.3–0.8) | 0.5 (0.2–0.7) | 0.3 (−0.1–0.6) | 0.1 (−0.3–0.5) |
| High | |||||
| Mean (SD) | 38.3 (27.2) | 413.1 (67.9) | 86.3 (8.9) | 22.6 (31.5) | 24.0 (10.9) |
| Mean difference from PSG (SD) | 46.6 (48.5) | −72.9 (57.9) | −14.6 (11.4) | 16.1 (34.8) | 2.2 (17.0) |
| Lin’s CCC (95% CI) | 0.3 (0.1–0.5) | 0.4 (0.2–0.7) | 0.3 (0.1–0.5) | 0.4 (0.0–0.7) | 0.1 (−0.3–0.5) |
| Automatic | |||||
| Mean (SD) | 28.3 (22.2) | 427.2 (72.6) | 89.1 (9.0) | 18.9 (30.7) | 22.9 (20.2) |
| Mean difference from PSG (SD) | 56.5 (47.0) | −87.0 (59.9) | −17.5 (11.5) | 19.8 (33.1) | 3.4 (25.2) |
| Lin’s CCC (95% CI) | 0.3 (0.1–0.4) | 0.4 (0.2–0.6) | 0.3 (0.1–0.4) | 0.4 (0.1–0.7) | −0.1 (−0.4–0.3) |
| Satisfactory a priori differences‡ | ≤ 30 minutes | ≤ 30 minutes | ≤ 5% | – | – |
†Mean difference between PSG and actigraphy. Positive values (actigraphy underestimates) and negative values (actigraphy overestimates) the variable. ‡Prior research defined differences (a priori) between actigraphy and PSG that are considered satisfactory.46 CI = confidence interval, Lin’s CCC = Lin’s Concordance Correlation Coefficient, PSG = polysomnography, SD = standard deviation.