Neuropsychiatric Symptoms and Cognitive Impairment: Understanding the Importance of Co-Morbid Symptoms

Abstract Background: Neuropsychiatric symptoms (NPS) are common in older adults with cognitive impairment, yet little is known about population-based prevalence and clinical implications of co-morbid symptom presentation across the spectrum from normal cognition to dementia. Objective: To characterize the prevalence of NPS and explore the clinical implications of co-morbid symptom presentation. Methods: Cross-sectional study of 1,417 older adults (aged 73–79) with dementia (n = 40); with mild cognitive impairment (MCI; n = 133); who are ‘cognitively normal, but-at-risk’ (CN-AR; n = 397); and who are cognitively normal (n = 847). NPS were assessed by the Neuropsychiatric Inventory. Cluster analyses were conducted using a latent class analysis (LCA). Results: NPS are highly prevalent across the cognitive function spectrum (30.8% –80%). NPS were associated with a 3-fold increased risk of dementia, a 2-fold increased risk of MCI, and a 1.5-times increased risk of CN-AR. Each additional co-morbid symptom was associated with an additional 1.5-times increased risk of dementia, but not MCI or CN-AR. LCA revealed four distinctive sub-populations: 1) frontal/low comorbidity; 2) high prevalence/high comorbidity; 3) affective/low comorbidity; and 4) sleep/low comorbidity. Conclusion: Our findings confirm previous reports on the prevalence of NPS in community-based samples and are consistent with the profiles of NPS domain characteristics of MCI and dementia. Number of co-morbid NPS and not symptom clusters are associated with increased risk of dementia. Understanding such patterns will help inform our understanding of mild behavioral disorders and assist with clinical assessmentMEM is supported by the Australian National Health and Medical Research Council (NHMRC) and Australian Research Council (ARC) Dementia Research Development Fellowship #1102028. RB is supported by the ARC Centre of Excellence in Population Ageing Research Project No. CE110001029. KJA is funded by NHMRC Fellowship #1102694. Wave 4 of the PATH Through Life Study was funded by NHMRC Grant #1002160. We would also like to acknowledge support from the Australian Research Council (ARC) CE110001029