Table 4. Two-level random intercept regressions investigating the effect of menstrual (= 1) vs. pre-menstrual (= 0) phase on sleep variables, based on menstrual cycles recorded in 15 female endurance athletes.
| Within-level effect of the menstrual phase on the DV | Between-level variance in the DV | |||||||
|---|---|---|---|---|---|---|---|---|
| DV | ICC | Est. | S.E. | p-value | R2 | Est. | S.E. | p-value |
| Time in bed (h) | .04 | .13 | .13 | .313 | .2% | .08 | .04 | .024 |
| Sleep onset latency (h) | .33 | .02 | .07 | .825 | < .05% | .08 | .06 | .172 |
| Total sleep time (h) | .00 | -.16 | .11 | .146 | .5% | .00 | .05 | .954 |
| Light sleep (h) | .03 | -.20 | .10 | .040 | 1.4% | .02 | .03 | .465 |
| Light sleep (%) | .11 | 1.36 | .89 | .126 | 1.1% | 4.49 | 2.91 | .122 |
| Deep sleep/slow wave (h) | .20 | .07 | .04 | .055 | 1.2% | .03 | .01 | .024 |
| Deep sleep/slow wave (%) | .16 | -1.26 | .51 | .013 | 1.8% | 4.04 | 1.93 | .013 |
| REM sleep (h) | .04 | -.03 | .07 | .673 | .1% | .01 | .01 | .282 |
| REM sleep (%) | .08 | .05 | .77 | .953 | < .05% | 1.76 | 1.58 | .265 |
| REM sleep latency (h) | .04 | -.28 | .11 | .011 | 3.3% | .02 | .02 | .359 |
| Sleep efficiency (%) | .22 | -2.46 | 1.28 | .054 | 2.0% | 19.85 | 7.54 | .008 |
REM = rapid eye movement; DV = dependent variable; ICC = intra-class correlation; Est. = estimate; S.E. = standard error; R2 = explained variance in %. Regressions were clustered on participant. Values are unstandardized. Significant results are highlighted in bold.