Does Structured Exercise Improve Cognitive Impairment in People with Mild to Moderate Dementia? A Cost-Effectiveness Analysis from a Confirmatory Randomised Controlled Trial: The Dementia and Physical Activity (DAPA) Trial

Background Previous studies suggest that physical exercise could slow dementia progression. However, evidence for the cost effectiveness of structured exercise is conflicting and based on small trials. Objectives The objective of this study was to compare the cost effectiveness of a tailored, structured, moderate- to high-intensity exercise programme versus usual care in people with mild to moderate dementia. Methods An economic evaluation was conducted from the UK National Health Service and personal social services perspective, based on data from a large randomised controlled trial. The primary clinical outcome was the participant reported ADAS-Cog (Alzheimer's Disease Assessment Scale-Cognitive Subscale) at 12 months. Costs (; pound 2014-2015 prices) were collected prospectively over a 12-month follow-up period. A bivariate regression of costs and quality-adjusted life-years (QALYs), with multiple imputation of missing data, was conducted with the view to estimating the incremental cost per QALY gained and the incremental net monetary benefit (INMB) associated with the exercise programme plus usual care versus usual care. Sensitivity analyses were undertaken to assess the impact of uncertainty surrounding aspects of the economic evaluation, and pre-specified subgroup analyses explored heterogeneity in the cost-effectiveness results. Results Participants (n= 494) were randomised to exercise plus usual care or usual care only. By 12 months the mean ADAS-Cog score had worsened slightly to 25.2 (standard deviation [SD] 12.3) in the exercise arm and 23.8 (SD 10.4) in the usual care: difference - 1.4, 95% confidence interval (CI) - 2.6 to - 0.2 (p =0.03). The mean (standard error [SE]) costs over 12 months for experimental versus control was 5945 pound (US$7856) versus 4597 pound (US$6574), respectively; (difference: 1347 pound [$1926]; p = 0.0426). Mean (SE) QALY estimates were 0.787 (0.012) versus 0.826 (0.019), respectively (p = 0.090). The probability that the exercise programme is cost effective was <1% across cost-effectiveness thresholds. INMBs ranged between -2601 pound (US$3719) and 2158 pound (US$3086) at cost-effectiveness thresholds between 15,000 pound (US$21,450) and 30,000 pound (US$42,900) per QALY. The cost-effectiveness results remained robust to several sensitivity and subgroup analyses. Conclusions Building on the clinical results of the trial, which showed that the structured exercise programme evaluated does not slow cognitive impairment in people with mild to moderate dementia, this economic evaluation shows that the programme is not cost effective.