Effectiveness and cost-effectiveness of behavioural support for prolonged abstinence for smokers wishing to reduce but not quit: Randomised controlled trial of physical activity assisted reduction of smoking (TARS)

Aims: For smokers unmotivated to quit, we assessed the effectiveness and cost-effectiveness of behavioural support to reduce smoking and increase physical activity on prolonged abstinence and related outcomes. Design: A multi-centred pragmatic two-arm parallel randomised controlled trial. Setting: Primary care and the community across four United Kingdom sites. Participants: Nine hundred and fifteen adult smokers (55% female, 85% White), recruited via primary and secondary care and the community, who wished to reduce their smoking but not quit. Interventions: Participants were randomised to support as usual (SAU) (n = 458) versus multi-component community-based behavioural support (n = 457), involving up to eight weekly person-centred face-to-face or phone sessions with additional 6-week support for those wishing to quit. Measurements: Ideally, cessation follows smoking reduction so the primary pre-defined outcome was biochemically verified 6-month prolonged abstinence (from 3–9 months, with a secondary endpoint also considering abstinence between 9 and 15 months). Secondary outcomes included biochemically verified 12-month prolonged abstinence and point prevalent biochemically verified and self-reported abstinence, quit attempts, number of cigarettes smoked, pharmacological aids used, SF12, EQ-5D and moderate-to-vigorous physical activity (MVPA) at 3 and 9 months. Intervention costs were assessed for a cost-effectiveness analysis. Findings: Assuming missing data at follow-up implied continued smoking, nine (2.0%) intervention participants and four (0.9%) SAU participants achieved the primary outcome (adjusted odds ratio, 2.30; 95% confidence interval [CI] = 0.70–7.56, P = 0.169). At 3 and 9 months, the proportions self-reporting reducing cigarettes smoked from baseline by ≥50%, for intervention versus SAU, were 18.9% versus 10.5% (P = 0.009) and 14.4% versus 10% (P = 0.044), respectively. Mean difference in weekly MVPA at 3 months was 81.6 minutes in favour of the intervention group (95% CI = 28.75, 134.47: P = 0.003), but there was no significant difference at 9 months (23.70, 95% CI = −33.07, 80.47: P = 0.143). Changes in MVPA did not mediate changes in smoking outcomes. The intervention cost was £239.18 per person, with no evidence of cost-effectiveness. Conclusions: For United Kingdom smokers wanting to reduce but not quit smoking, behavioural support to reduce smoking and increase physical activity improved some short-term smoking cessation and reduction outcomes and moderate-to-vigorous physical activity, but had no long-term effects on smoking cessation or physical activity.