To determine if cognitive function is still related to overall functional impairment in profound dementia.

The Baylor Profound Mental Status Exam (BPMSE) was developed to assess cognitive function in profound dementia stage. The Clinical Dementia Rating (CDR) scale has been widely used in measuring functional performance in dementia.

We recruited 864 probable Alzheimer’s disease (AD) and 55 possible dementia with Lewy body (DLB) cases with profound dementia by MMSE or/and clinical global impression. We used BPMSE to measure cognitive function, and the CDR sum of boxes (CDR-SB) score to determine overall functional status. We used Spearman’s rank order correlation to examine the univariate association between CDR-SB and BPMSE in the two diagnostic groups separately, and multivariable regression analysis to investigate if BPMSE remained associated with functional decline after adjustment for age, sex, education, and APOE genotype. We expected to see an inverse correlation between BPMSE and CDR-SB scores based on the directionality of the rating scale scoring.

In both AD and DLB, total BPMSE score significantly correlated with CDR-SB score (AD: r = -0.453, p < 0.001; DLB: r = -0.489, p = 0.013). Interestingly, in DLB, the “attention” domain of BPMSE had the strongest association with CDR-SB (r = -0.700, p < 0.001) compared to other domains. The multivariable regression models showed that higher BPMSE scores (i.e., better cognitive function) were correlated with lower CDR-SB scores (i.e., better global function) in AD (CDR-SB: β = -0.340, p < 0.001) but not as strongly in DLB (CDR-SB: β = -0.298, p = 0.174).

In AD and DLB patients who enter the profound dementia stage, cognitive function is associated with the severity of functional impairment. The lack of significance for DLB in multivariable regression could be due to small sample size, as the correlation magnitude is similar to that in AD.