Frequency and subgroups of neuropsychiatric symptoms in mild cognitive impairment and different stages of dementia in Alzheimer's disease

Background: Neuropsychiatric symptoms (NPS), such as depression, apathy, agitation, and psychotic symptoms are common in mild cognitive impairment (MCI) and dementia in Alzheimer's disease (AD). Subgroups of NPS have been reported. Yet the relationship of NPS and their subgroups to different stages of cognitive impairment is unclear. Most previous studies are based on small sample sizes and show conflicting results. We sought to examine the frequency of NPS and their subgroups in MCI and different stages of dementia in AD. Methods: This was a cross-sectional study using data from a Norwegian national registry of memory clinics. From a total sample of 4,571 patients, we included those with MCI or AD (MCI 817, mild AD 883, moderate-severe AD 441). To compare variables across groups ANOVA or (2)-test was applied. We used factor analysis of Neuropsychiatric Inventory Questionnaire (NPI-Q) items to identify subgroups of NPS. Results: The frequency of any NPS was 87.2% (AD 91.2%, MCI 79.5%; p < 0.001) and increased with increasing severity of cognitive decline. The most frequent NPS in MCI was depression. Apathy was the most frequent NPS in AD across different stages of severity. The factor analysis identified three subgroups in MCI and mild AD, and a fourth one in moderate-severe AD. We labelled the subgroups depression, agitation, psychosis, and elation. Conclusions: The frequency of NPS is high in MCI and AD and increases with the severity of cognitive decline. The subgroups of NPS were relatively consistent from MCI to moderate-severe AD. The subgroup elation appeared only in moderate-severe AD.