Text messaging with or without financial incentives versus a waitlist control for weight loss in men: cost-effectiveness analysis of the Game of Stones randomised controlled trial

Background
Cost-effective weight loss interventions are needed for people with obesity, particularly men, who are less likely to engage with weight loss programmes. This study aimed to investigate the cost-effectiveness of text messaging plus financial incentives and text messaging alone compared to a waitlist control to help men lose weight.

Methods
585 men with obesity were recruited to Game of Stones (GoS): a 3-arm randomised controlled trial in 3 UK areas. Text messaging alone participants received daily automated behavioural texts for 12-months (3% weight loss). Text messaging with financial incentives participants also received loss-framed financial incentives linked to achieving weight loss targets at 12-months (5% significant weight loss). A control group received no intervention for 12 months (1.3% weight loss) followed by 3 months of texts. We conducted a 24-month within-trial cost-effectiveness analysis and lifetime decision model from a UK NHS perspective. The PRIMEtime model extrapolated the impact of GoS weight-loss data on lifetime obesity related disease incidence, costs, and QALYs. Weight regain assumptions were explored in scenario analyses.

Findings
Text messaging with financial incentives costs £243 and text messaging alone costs £110 per participant to deliver. There were no significant differences between 24-month total costs or QALYs across groups. When modelled over lifetime, the mean discounted QALYs per person were 12.48, 12.49, and 12.46 for text messaging with financial incentives, text messaging alone, and waitlist control, respectively. The corresponding mean discounted total costs per person were £15,277, £15,117, and £15,100. The between group results for text messaging with financial incentives versus control were: QALY difference (95% CI): 0.02 (0.007, 0.029); cost difference: £176 (£43; £311); Incremental cost-effectiveness ratio (ICER): £9748 (£7,705, £11,791). For text messaging alone versus control: QALY difference: 0.03 (0.015, 0.037); cost difference: £16.5 (-£117; £152); ICER: £628 (£-5,914, £5384).

Interpretation
Text messaging with financial incentives and text messaging alone are cost-effective compared to waitlist control. Both are relatively low-cost interventions that can be scaled to improve weight loss for men. The optimal strategy between them depends on weight regain assumptions after 12 months.