Background:Behavioral and psychological symptoms of dementia (BPSD) manifest in the early stages of the disease and impair patients’ and caregivers’ quality of life.Objective:To assess the effectiveness of the nutritional supplement Fortasyn Connect on BPSD for 12 months in people with mild cognitive impairment (MCI) and dementia in clinical practice.Methods:Retrospective, national, single-center study of 236 patients (158 MCI and 78 dementia; 55.1% of AD etiology). BPSD were assessed with the Neuropsychiatric Inventory (NPI) at month 3, 6, and 12. Cognition (Mini-Mental State Examination, MMSE), depression (Geriatric Depression Scale, GDS), and everyday functioning (Blessed Dementia Scale, BLS-D; Rapid Disability Rating Scale 2, RDRS2) were also evaluated.Results:Total NPI score, caregiver impact, and symptoms of depression, anxiety, apathy, and irritability improved after 3, 6, and 12 months from Fortasyn Connect initiation (p< 0.001). NPI decreases were more pronounced when baseline NPI score was higher than > 20 points (p< 0.001). The benefit was independent of gender, age, diagnosis, etiology, or concomitant treatment (p< 0.0001), although larger decreases in NPI total score were observed in MCI patients (p< 0.0001). After 12 months, GDS scores decreased (p= 0.042), and MMSE, BLS-D, and RDRS 2 scores remained stable.Conclusion:Fortasyn Connect improved BPSD over at least a year in patients with MCI and dementia. Depression, anxiety, apathy, and irritability were the symptoms that improved the most. The benefit was independent of patients’ characteristics and treatment but was greater if prescribed early and when baseline NPI scores were higher.