Table 2.
Multivariate linear mixed regression model for changes in sleep measures over time
| Variables entered (all in one block) | Pittsburgh Sleep Quality Index (score) |
Nighttime total sleep time (minutes) |
Nighttime wake after sleep onset (minutes) |
Nighttime sleep percent (%) |
Daytime total sleep time (minutes) |
|||||
|---|---|---|---|---|---|---|---|---|---|---|
| Estimate ± SE | P | Estimate ± SE | P | Estimate ± SE | P | Estimate ± SE | P | Estimate ± SE | P | |
| Intercept | 5.96 ± 0.47 | < 0.001 | 440.53 ± 11.50 | < 0.001 | 75.85 ± 5.54 | < 0.001 | 85.40 ± 1.01 | < 0.001 | 58.47 ± 7.85 | < 0.001 |
| Caregiver | 0.29 ± 0.63 | 0.446 | 4.45 ± 13.74 | 0.746 | 0.08 ± 6.27 | 0.956 | 0.19 ± 1.21 | 0.877 | − 3.32 ± 8.62 | 0.598 |
| Age, baseline | 0.03 ± 0.03 | 0.245 | 0.86 ± 0.67 | 0.197 | 0.38 ± 0.30 | 0.268 | −0.04 ± 0.06 | 0.498 | 1.69 ± 0.41 | < 0.001 |
| Gender, female | 0.78 ± 0.47 | 0.081 | 0.04 ± 10.23 | 0.997 | −7.85 ± 4.62 | 0.073 | 1.44 ± 0.90 | 0.118 | −2.24 ± 6.31 | 0.576 |
| Education | 0.02 ± 0.07 | 0.761 | −0.05 ± 1.54 | 0.973 | −1.00 ± 0.70 | 0.143 | 0.18 ± 0.14 | 0.195 | 1.16 ± 0.95 | 0.341 |
| Health problems | 0.01 ± 0.08 | 0.898 | −2.97 ± 1.96 | 0.131 | −0.10 ± 0.94 | 0.796 | −0.01 ± 0.17 | 0.994 | 0.89 ± 1.33 | 0.814 |
| Body mass index | 0.04 ± 0.04 | 0.450 | −0.95 ± 0.82 | 0.249 | 0.71 ± 0.38 | 0.122 | −0.16 ± 0.07 | 0.025 | 1.49 ± 0.54 | 0.005 |
| Alcohol consumption | −0.03 ± 0.03 | 0.329 | −0.58 ± 0.67 | 0.383 | −0.01 ± 0.31 | 0.945 | −0.01 ± 0.06 | 0.983 | −0.60 ± 0.44 | 0.362 |
| Physical activity | 0.02 ± 0.08 | 0.336 | −3.40 ± 2.05 | 0.097 | −1.12 ± 1.00 | 0.224 | 0.12 ± 0.18 | 0.502 | 0.95 ± 1.42 | 0.859 |
| Ever smoker | −0.38 ± 0.37 | 0.354 | 9.82 ± 8.46 | 0.247 | −0.25 ± 3.94 | 0.964 | 0.25 ± 0.74 | 0.736 | −1.02 ± 5.47 | 0.418 |
| Years caregiving | −0.01 ± 0.07 | 0.598 | 1.91 ± 1.49 | 0.200 | −0.15 ± 0.67 | 0.906 | 0.07 ± 0.13 | 0.609 | 0.61 ± 0.92 | 0.462 |
| Role overload | 0.23 ± 0.05 | < 0.001 | 0.37 ± 1.32 | 0.777 | 0.40 ± 0.64 | 0.493 | −0.08 ± 0.12 | 0.474 | −1.10 ± 0.90 | 0.306 |
| Depressive symptoms | 0.18 ± 0.03 | < 0.001 | 0.61 ± 0.67 | 0.358 | −0.01 ± 0.32 | 0.974 | 0.02 ± 0.06 | 0.784 | 0.53 ± 0.46 | 0.186 |
| Interleukin-6 | 0.09 ± 0.39 | 0.652 | 6.72 ± 9.86 | 0.496 | −0.47 ± 4.81 | 0.942 | 0.41 ± 0.87 | 0.623 | −0.18 ± 6.86 | 0.682 |
| TNF-α | 1.27 ± 0.71 | 0.165 | 18.73 ± 17.46 | 0.284 | −0.22 ± 8.59 | 0.851 | 0.04 ± 1.53 | 0.974 | 6.66 ± 12.32 | 0.603 |
| Time | 0.19 ± 0.13 | 0.096 | −3.32 ± 3.18 | 0.296 | −0.76 ± 1.57 | 0.374 | 0.08 ± 0.28 | 0.808 | 2.63 ± 2.27 | 0.269 |
| Placed spouse | 0.17 ± 0.43 | 0.531 | 2.63 ± 11.16 | 0.814 | 3.34 ± 5.47 | 0.522 | −0.72 ± 0.98 | 0.466 | −9.92 ± 7.82 | 0.132 |
| Spouse deceased | 0.96 ± 0.51 | 0.058 | 11.45 ± 14.01 | 0.415 | 22.78 ± 6.89 | 0.002 | −3.20 ± 1.23 | 0.009 | 29.27 ± 9.88 | 0.003 |
All variables were centered to the mean such that the intercept shows the average value of the 5 sleep measures in the entire sample. Categorical variables were contrast coded as caregiver (+0.5) vs. non-caregiver (−0.5), female gender (+0.5) vs. male gender (−0.5), and ever smoker (+0.5) vs. never smoker (−0.5). “Placed Spouse” and “Spouse Deceased” indicate the immediate change in the sleep measures assessed 3 months after the respective transition. “Time” indicates the change in sleep measures per each assessment the participant was in the study. TNF-α, tumor necrosis factor-α. Estimates ± SE are given in original units.