Table 4.
Associations of sleep measures with mortality
| Unadjusted | Adjusteda | ||
|---|---|---|---|
| Variable | HR (95% CI) | HR (95% CI) | P Value (FDR-Correctedb) |
| Hypoxemia-based measures | |||
| Apnea hypopnea index, for every 5 events/h higherc | 1.02 (0.99 to 1.06)d | 1.01 (0.96 to 1.05)d | 0.99 |
| Nocturnal hypoxemia (% of sleep time with oxygen saturation <90%), for every 15% highere,f | 1.53 (1.30 to 1.78) | 1.36 (1.12 to 1.67) | 0.007 |
| Mean oxygen saturation, for every 2% lowerf | 1.76 (1.47 to 2.14) | 1.59 (1.23 to 2.08) | 0.003 |
| Oxygen desaturation index, for every 17 events/h highere,f | 1.19 (1.03 to 1.38) | 1.02 (0.84 to 1.25) | 0.99 |
| Other polysomnography measures | |||
| Total sleep, for every h lowerg,c | 1.22 (1.08 to 1.36)h | 1.06 (0.93 to 1.22)h | 0.88 |
| Sleep efficiency, for every 15% lowerf | 1.40 (1.15 to 1.69) | 1.08 (0.83 to 1.40) | 0.99 |
| Periodic leg movement index, for every 57 events/h higherf | 1.32 (1.06 to 1.63) | 1.00 (0.79 to 1.32) | 0.99 (0.99) |
HR, hazard ratio; 95% CI, 95% confidence interval; FDR, false discovery rate.
Adjusted model is adjusted for age, sex, race, diabetes, body mass index, kidney function status (CKD or ESKD), and time-varying kidney transplant status. Within each model, HR estimates and the corresponding P value are given.
FDR-corrected P values used Benjamini–Hochberg method.
On the basis of clinically meaningful increment.
For apnea hypopnea index, the HR for every 25 events/h (1 SD) higher were as follows: unadjusted HR, 1.10 (95% CI, 0.95 to 1.34) and adjusted HR, 1.05 (95% CI, 0.82 to 1.28).
There was a significant interaction between nocturnal hypoxemia and CKD/ESKD (P=0.01) and between oxygen desaturation index and sex (P=0.02), so HRs within these subgroups were also calculated from the adjusted model. The adjusted HR for every 15% higher nocturnal hypoxemia for CKD and ESKD, respectively, were HR, 2.39 (95% CI, 1.55 to 3.65; P<0.001) and HR, 1.15 (95% CI, 1.00 to 1.55; P=0.07). Because of the small sample size for women, the HR estimates for oxygen desaturation index by sex were not shown.
On the basis of 1 SD increment.
For adjusted analysis, the proportional hazard assumption did not hold for total sleep time. Thus, an interaction term with time was included and HRs at different time points (year 1, year 5, year 9, and year 12) were calculated but revealed estimates in the same direction as the overall HR (data not shown).
For total sleep, the HR for every 1.86 hour (1 SD) lower were as follows: unadjusted HR, 1.44 (95% CI, 1.15 to 1.77) and adjusted HR, 1.11 (95% CI, 0.87 to 1.45).