Modelling the cost-effectiveness of environmental interventions to encourage and support physical activity

Abstract

BackgroundPhysical inactivity is a major cause of premature death and disease costing the English National Health Service around £1.2 billion per year. A review of the cost-effectiveness of environmental interventions to increase physical activity found insufficient evidence to inform the development of a national guideline on this topic. This study used an economic model to assess the cost-effectiveness of such interventions. MethodsA model was developed to determine the relative cost-effectiveness for different combinations of cost and physical activity improvement, along with five case-study interventions. A baseline physical activity distribution was estimated using the 2014 Health Survey for England, which was then adjusted by intervention effectiveness. These changes in physical activity were then associated with changes in the risk of mortality and of developing five comorbidities. These data were used to estimate the costs and benefits, in quality-adjusted life years (QALYs), to the health sector of each intervention against a background of do nothing. Results were reported as incremental cost-effectiveness ratios (ICERs). Sensitivity analyses explored the uncertainty associated with various model parameters including effectiveness, costs, and mortality risk reduction. FindingsThe threshold analysis, which assumed no decay over time in intervention effectiveness, showed that small average increases in physical activity could be cost-effective, depending on the intervention cost. For example, an intervention costing £50 per person would be cost-effective if it motivated the average person to walk for an additional 4 min per day. The analysis also showed that interventions for populations with limited mobility are more cost-effective, since the expected health benefits are larger. Four multicomponent interventions, involving public transport, cycle lane, and open space modifications, could be highly cost-effective with ICERs of less than £8000. A park renovation study, with a cost estimate of over £200 per person, was not cost-effective (£207 316 per QALY). Sensitivity analyses showed that the conclusions were robust even to large changes in the parameter inputs. InterpretationThe analysis shows that environmental interventions to increase physical activity can be highly cost-effective, even if the benefits are small. Unlike previous models informing guidance by the National Institute for Health and Care Excellence (NICE), this model used a continuous measure of physical activity and accounts for changes in both morbidity and mortality. However, these findings are dependent on locally varying factors such as intervention cost. The threshold analyses provide decision makers with information on how cost-effective an intervention will be for differing levels of cost and physical activity improvement. FundingNational Institute for Health and Care Excellence (NICE).