Table 5.

Relationship between overall spindle frequency and potential moderators

	$\beta$ original	t original	$\beta$ rankit	t rankit
Duration (s)	−0.186	−33.337	−0.179	−44.677
Intra spindle SD (Hz)	−0.444	−148.269	−0.350	−161.300
Amplitude (µV)	−1.6e-03	−68.855	-0.001	−71.837
High γ power (µV2)	0.238	64.020	0.192	66.682
Frequency change (Hz/s)	−0.004	−10.802	−0.006	−20.007

This model also controlled for the effect of brain region, sleep stage, and the frequency of seizures per patient (coded as low, medium, or high). the first two columns correspond to the slope estimates from the LMEM for each spindle characteristic and overall spindle frequency. The next two columns represent model estimates after rank inverse normal transformation of the data (rankit) and removing residuals that fall outside of ±2 SDs (to mitigate the influence of extreme observations on the estimates). All measures show no change in significance after transformation (with p < 0.05 as |t| > 1.96). QQ plots for both models are shown in Extended Data Table 5-1.