Table 2.
Univariate Association Between Slow Wave Sleep Quartile and Confounders
| Quartile of slow wave sleep (SWS as a % of total sleep time) |
P-value (for trend) | ||||
|---|---|---|---|---|---|
| Quartile 1 0% to ≤ 3.8% (n = 688) | Quartile 2 > 3.8% to ≤ 9.9% (n = 685) | Quartile 3 > 9.9% to ≤ 16.7% (n = 686) | Quartile 4 > 16.7% (n = 686) | ||
| Age (years), mean ± SD | 77.2 ± 5.7 | 76 ± 5.4 | 75.9 ± 5.4 | 76.4 ± 5.5 | <0.0001 |
| Race/ethnicity-non-Caucasian, n (%) | 80 (11.6) | 64 (9.3) | 62 (9.0) | 46 (6.7) | 0.018 |
| Physical activity (PASE Score), mean ± SD | 143 ± 73 | 147 ± 73 | 153 ± 71 | 143 ± 69 | 0.018 |
| History of diabetes mellitus, n (%) | 100 (14.5) | 87 (12.7) | 86 (12.5) | 85 (12.4) | 0.608 |
| History of cardiovascular disease, n (%) | 312 (45.4) | 283 (41.4) | 274 (40.0) | 281 (41.0) | 0.188 |
| History of hypertension, n (%) | 350 (50.9) | 337 (49.2) | 344 (50.2) | 339 (49.4) | 0.924 |
| History of chronic lung disease, n (%) | 92 (13.4) | 88 (12.9) | 92 (13.4) | 100 (14.6) | 0.817 |
| Smoking (current or prior), n (%) | 404 (58.72) | 413 (60.29) | 406 (59.18) | 426 (62.1) | 0.585 |
| Pack-years smoked, mean ± SD | 16 ± 23 | 17 ± 25 | 16 ± 23 | 16 ± 22 | 0.876 |
| RDI (events/hr), mean ± SD | 15.2 ± 16.0 | 11.7 ± 12.5 | 10.1 ± 11.0 | 9.9 ± 11.0 | <0.0001 |
| RDI ≥ 15, n (%) | 244 (35%) | 174 (25%) | 154 (22%) | 151 (22%) | <0.0001 |
| RDI ≥ 5, n (%) | 471 (68%) | 420 (61%) | 391 (57%) | 386 (56%) | <0.0001 |
| CAI, mean ± SD | 1.84 ± 5.02 | 1.48 ± 4.06 | 1.32 ± 3.42 | 1.31 ± 3.84 | 0.511 |
| CAI ≥ 5, n (%) | 59 (9%) | 50 (8%) | 44 (7%) | 45 (7%) | 0.375 |
| Total sleep time (min), mean ± SD | 344.1 ± 72.5 | 360.6 ± 67.7 | 360.8 ± 65.8 | 358.3 ± 67.9 | <0.0001 |
| Sleep efficiency (%), mean ± SD | 71.1 ± 12.8 | 73.9 ± 12.2 | 75.3 ± 11.2 | 75.7 ± 11.9 | <0.0001 |
SD = standard deviation, RDI = respiratory disturbance index, CAI = central apnea index
P-value is from comparison across quartiles of SWS using ANOVA (continuous variables with normal distribution), Kruskal-Wallis test (continuous variable with skewed distribution) or chi-square test (categorical variables)