Table 4.

Unadjusted and Adjusted Discrete-Time Proportional Hazards Models for Activity Frequency Predicting Time-to-Dementia Diagnosis

	Model 1 (unadjusted)			Model 2 (adjusted)			Model 3 (stratified by MCI)
							Non-MCI (n = 2,587)			MCI (n = 481)
	HR	95% CI	p value	HR	95% CI	p value	HR	95% CI	p value	HR	95% CI	p value
Activity frequency
Intellectual	0.937	0.91, 0.96	<.001***	0.932	0.91, 0.96	<.001***	0.946	0.91, 0.98	.001**	0.976	0.93, 1.02	.273
Physical	1.002	0.99, 1.01	.747	1.008	1.00, 1.02	.194	1.008	0.99, 1.02	.286	0.994	0.98, 1.01	.514
Social	0.970	0.93, 1.01	.124	0.975	0.94, 1.01	.214	0.981	0.93, 1.03	.430	0.982	0.92, 1.05	.607
Mean cross-validated AUC			.673			.733

Notes: AUC = area under the curve; CI = confidence interval; HR = hazard ratio; MCI = mild cognitive impairment. Model 1 is unadjusted for covariates. Model 2 is adjusted for demographic (baseline age, study site, treatment group, sex, race, education category) and health covariates (medical comorbidities, significant depressive symptoms). Model 3 is stratified by MCI status. Activity frequency scores represent average frequency of engagement within the specified activity domain (intellectual, physical, social). Mean 10-fold cross-validated area under the receiver operating characteristic curves are reported for nonstratified models.

**p < .01. ***p < .001, all p values are 2-sided.