BackgroundDepression and dementia are highly prevalent in older adults and often co-occur. This Phase IV study investigated the effectiveness and tolerability of vortioxetine in improving depressive symptoms, cognitive performance, daily and global functioning and health-related quality of life (HRQoL) in patients with major depressive disorder (MDD) and comorbid early-stage dementia. MethodsPatients (n = 82) aged 55–85 years with a primary diagnosis of MDD (onset before age 55 years) and comorbid early-stage dementia (diagnosed ≥6 months before screening and after onset of MDD; Mini-Mental State Examination-2 total score, 20–24) received vortioxetine for 12 weeks (initiated at 5 mg/day and up-titrated to 10 mg/day at day 8, with flexible dosing thereafter [5–20 mg/day]). The primary endpoint was change from baseline in Montgomery–Åsberg Depression Rating Scale (MADRS) total score at week 12. ResultsSignificant improvement in depressive symptom severity was seen from week 1 onwards (P < 0.0001). At week 12, the least-square mean (standard error) change in MADRS total score from baseline was −12.4 (0.78). Significant improvements in cognitive performance were observed (from week 1 for the Digit Symbol Substitution Test and week 4 for the Rey Auditory Verbal Learning Test). Patients also experienced significant improvements in daily and global functioning, and HRQoL. Vortioxetine was well tolerated. From week 4 onwards, more than 50 % of patients were receiving 20 mg/day. LimitationsOpen-label study. ConclusionsVortioxetine demonstrated effectiveness in clinically significantly improving depressive symptoms, cognitive performance, daily and global functioning, and HRQoL in patients with MDD and comorbid early-stage dementia treated for 12 weeks. Trial registrationClinicalTrials.gov/ct2/show/NCT04294654.