Depression is common in people with dementia, and negatively affects quality of life.

This paper aims to evaluate the cost-effectiveness of an intervention for depression in mild and moderate dementia caused by Alzheimer's disease over 12 months (PATHFINDER trial), from both the health and social care and societal perspectives.

A total of 336 participants were randomised to receive the adapted PATH intervention in addition to treatment as usual (TAU) (n = 168) or TAU alone (n = 168). Health and social care resource use were collected with the Client Service Receipt Inventory and health-related quality-of-life data with the EQ-5D-5L instrument at baseline and 3-, 6- and 12-month follow-up points. Principal analysis comprised quality-adjusted life-years (QALYs) calculated from the participant responses to the EQ-5D-5L instrument.

The mean cost of the adapted PATH intervention was estimated at £1141 per PATHFINDER participant. From a health and social care perspective, the mean difference in costs between the adapted PATH and control arm at 12 months was −£74 (95% CI −£1942 to £1793), and from the societal perspective was −£671 (95% CI −£9144 to £7801). The mean difference in QALYs was 0.027 (95% CI −0.004 to 0.059). At £20 000 per QALY gained threshold, there were 74 and 68% probabilities of adapted PATH being cost-effective from the health and social care and societal perspective, respectively.

The addition of the adapted PATH intervention to TAU for people with dementia and depression generated cost savings alongside a higher quality of life compared with TAU alone; however, the improvements in costs and QALYs were not statistically significant.