Missing data analysis in drug-naïve Alzheimer's disease with behavioral and psychological symptoms

To clarify the effects of missing values due to behavioral and psychological symptoms in dementia (BPSD) in Alzheimer's disease (AD) patients on the neuropsychological tests, this study describes the pattern of missing values due to BPSD, and its influence on tests.

Drug-naïve probable AD patients (n=127) with BPSD and without BPSD (n=32) were assessed with Seoul Neuropsychological Screening Battery including measures of memory, intelligence, and executive functioning. Moreover, patients were rated on Korean Neuropsychiatry Inventory (K-NPI).

The more severe the K-NPI score, the less neuropsychological tests were assessable, leading to many missing values. Patients with BPSD were more severely demented than those without BPSD. K-NPI scores were significantly correlated with the number of missing values. The effect of BPSD was largest for tests measuring frontal functions. The replacement of the missing values due to BPSD by the lowest observed score also showed the largest effect on tests of frontal function.

The global cognitive and behavior scales are related with missing values. Among K-NPI sub-domains, delusion, depressing, apathy, and aberrant motor behavior are significantly correlated for missing values. Data imputation of missing values due to BPSD provides a more differentiated picture of cognitive deficits in AD with BPSD.