Table 2.
Sample Characteristics by REM AHI Severity Category for the Subsample of Sleep Studies with non-REM AHI ≤ 5 in 1,216 Subjects (Multiple Studies per Subject)
| REM AHI Severity Category |
|||||
|---|---|---|---|---|---|
| <1 | 1–4.9 | 5–14.9 | ≥15 | Total | |
| Number of sleep studies, n (%) | 1,067 (36) | 912 (31) | 621 (21) | 353 (12) | 2,953 |
| Female, % | 45 | 54 | 50 | 42 | 48 |
| Race/ethnicity, white, % | 98 | 97 | 95 | 96 | 97 |
| Current smoking, % | 17 | 16 | 12 | 15 | 15 |
| Prevalent hypertension, % | 24 | 33 | 37 | 50 | 33 |
| Type 2 diabetes, % | 2 | 4 | 6 | 6 | 4 |
| Age, years, mean (SD) | 49 (9) | 52 (9) | 54 (9) | 56 (8) | 52 (10) |
| Body mass index, kg/m2, mean (SD) | 27 (5) | 28 (5) | 30 (6) | 33 (7) | 29 (6) |
| Waist-to-hip ratio, mean (SD) | 0.87 (0.09) | 0.89 (0.09) | 0.90 (0.09) | 0.90 (0.08) | 0.88 (0.09) |
| Total sleep time, min, mean (SD) | 377 (59) | 380 (57) | 381 (56) | 373 (56) | 378 (57) |
| REM sleep time, min, mean (SD) | 73 (25) | 73 (25) | 72 (24) | 66 (23) | 72 (25) |
| REM sleep time, percent of total sleep time, mean (SD) | 19 (5) | 19 (6) | 19 (5) | 18 (5) | 19 (5) |
| Slow wave sleep, min, mean (SD) | 43 (32) | 41 (35) | 37 (33) | 37 (34) | 40 (34) |
| Slow wave sleep, percent of total sleep time, mean (SD) | 12 (5) | 11 (9) | 10 (8) | 10 (9) | 11 (9) |
| AHI, events/h, mean (SD) | 0.4 (0.7) | 1.1 (0.9) | 2.4 (1.3) | 5.2 (2.7) | 1.6 (2.0) |
| non-REM AHI, events/h, mean (SD) | 0.6 (0.9) | 1.1 (1.2) | 1.8 (1.3) | 2.4 (1.3) | 1.2 (1.3) |
| REM AHI, events/h, mean (SD) | 0.2 (0.3) | 2.5 (1.1) | 9.0 (2.9) | 27 (11) | 5.9 (9.3) |
| Oxygen desaturation index, events/h, mean (SD)* | 0.7 (0.9) | 1.5 (1.1) | 3.2 (1.5) | 6.8 (2.9) | 2.7 (2.6) |
| non-REM oxygen desaturation index, events/h, mean (SD)* | 0.7 (1.0) | 1.1 (1.2) | 1.8 (1.3) | 2.5 (1.2) | 1.5 (1.3) |
| REM oxygen desaturation index, events/h, mean (SD)* | 0.2 (0.3) | 2.2 (1.2) | 8.2 (3.2) | 24.7 (10.8) | 7.3 (9.7) |
| Time below 90% Spo2, percent of total sleep time, mean (SD)† | 0.4 (2.0) | 1.3 (9.2) | 0.6 (2.2) | 1.4 (3.8) | 0.9 (5.5) |
| Time below 90% Spo2, percent of non-REM sleep time, mean (SD)† | 0.3 (1.9) | 1.2 (9.1) | 0.5 (2.2) | 0.9 (3.8) | 0.8 (5.5) |
| Time below 90% Spo2, percent of REM sleep time, mean (SD)† | 0.5 (3.8) | 1.6 (10.7) | 1.0 (3.3) | 3.6 (6.3) | 1.5 (7.0) |
| Epworth Sleepiness Scale, mean (SD)‡ | 8.3 (4.0) | 8.2 (4.0) | 8.5 (4.0) | 8.3 (3.9) | 8 (4) |
| Excessive daytime sleepiness, % | 20 | 17 | 22 | 20 | 20 |
Definition of abbreviations: AHI = apnea–hypopnea index; Spo2 = oxygen saturation by finger pulse oximetry.
*
Available on a subset of studies (n = 1,155) after implementation of full digital polysomnography in the Wisconsin Sleep Cohort.
†
Available on a subset of studies (n = 845) after implementation of full digital polysomnography in the Wisconsin Sleep Cohort.
‡
Available on a subset of studies (n = 2,276).