Table 4.

Results of linear mixed model analyses of the Symbol Digit Modalities Test results over time with random intercepts on subject level and time (in days).

			β (95% CI)		P value		Random effect variance, %			Explained variance, %
Intercept only								110.9			N/Aa
Cognition score cluster		–8.57 (–12.02 to –5.12)		<.001		82.7			25.4
Cognition score cluster and covariatesb		–5.02 (–9.02 to –1.02)		.02		77.1			30.4
Hybrid model (including covariatesa)								74.4			32.9
	Between subjects	–11.25 (–17.28 to –5.21)		<.001		N/A			N/A
	Within subjects	–0.35 (–5.60 to 4.89)		.9		N/A			N/A

^aN/A: not applicable.

^bCovariates included age, sex, and level of education.