A Descriptive Statistical Analysis of Neuropsychiatric Symptom Pair Prevalence

Neuropsychiatric symptoms (NPS) are very common and associated with high levels of distress, both in dementia patients and their caregivers. Especially at more advanced dementia disease stages, NPS rarely occur in isolation and the presence of two or more NPS may affect disease severity as well as the response to therapy. There is limited quantitative information on prevalence of specific symptom combinations in the general population, as well as in the populations recruited for symptom-specific investigations. We performed cross-sectional analyses of data from two longitudinal studies (Aging, Demographics, and Memory Study (ADAMS) and the National Alzheimer's Coordinating Center data (NACC)). In both studies and all Mini Mental State Examination (MMSE) strata, we observed every possible pair combination, from commonly recognized and discussed associations (e.g., hallucinations and delusions) to what might be seen as rather counter-intuitive patterns (e.g., apathy and agitation). In conclusion, prevalence of symptom pairs cannot be readily predicted based on prevalence of individual symptoms. Further, the presence of cognitive deficit and degree of cognitive impairment is associated with increased prevalence of all symptoms and symptom pairs, albeit to different degrees. The present study illustrates that, while there is the possibility of any combination of neuropsychiatric symptoms presenting during the course of dementia, their co-occurrence cannot be readily predicted based on the prevalence of individual symptoms. Thus, our study results serve as a source of reference information to inform the design and recruitment strategies for future clinical studies and epidemiological research on neuropsychiatric symptoms in people with dementia.