Background: Neuropsychiatric symptoms (NPS) affect the majority of patients who have dementia. Neuropsychiatric sub-syndromes with symptoms that occur together and have common neurobiological correlates have been identified. There are scarce data regarding the comparison of the pattern of the neuropsychiatric sub-syndromes in distinct ethnical and cultural populations. We aim at comparing the pattern of the NPS, and the factor analysis of the Neuropsychiatric Inventory (NPI-10) in two samples of outpatients with dementia living in Brazil and Norway.

Methods: This is a cross-sectional study. The sample consists of 168 Brazilian and 155 Norwegian demented patients from psychogeriatric facilities and community-based educational programs. Brazilian patients were diagnosed with Alzheimer's disease (63.7%), vascular dementia (15.5%), or mixed dementia (20.8%), whereas the diagnoses of Norwegian patients were Alzheimer's disease (97.4%) and mixed dementia (2.6%). Principal component analysis with the Varimax rotation was used for factor analysis of the NPI-10.

Results: Apathy (80.4 %), agitation/aggression (45.8%), and aberrant motor behavior (45.8%) were the most common symptoms in the Brazilian sample. Apathy (72.3%), dysphoria (61.9%), and anxiety (52.3%) were the most frequent symptoms in the Norwegian sample. Factor analysis of the NPI-10 revealed three syndromes for the Brazilian (Psychosis, Mood, Psychomotor) and Norwegian (Psychosis, Mood, Frontal) groups.

Conclusions: The frequency of individual NPS may differ among distinct populations. However, Psychosis and Depression are common sub-syndromes in diverse ethnical and cultural patients with dementia. Our findings support the syndromic approach for the clinical assessment of the patients with dementia.