Analytical approach:
A decision tree was developed to assess the costs and outcomes of the two options in a cohort of people aged 40 to 60 years. This model was based on a policy-relevant cost-effectiveness model developed for the National Institute for Health and Clinical Excellence (NICE). A lifetime horizon was adopted and the authors stated that the perspective was that of the UK NHS and Personal Social Services.
Effectiveness data:
The clinical and effectiveness data were from published studies. The main estimate of effectiveness was the probability of moving from a sedentary lifestyle to an active one, defined as doing at least 90 to 150 minutes of at least moderate intensity physical activity per week. This estimate was from a meta-analysis conducted in 2011 as part of a systematic review of the exercise referral scheme. Other important parameters were the relative risks of developing coronary heart disease, stroke, and type II diabetes, which were associated with physical inactivity. These estimates were from published literature, including a systematic review conducted for the NICE.
Monetary benefit and utility valuations:
The utility estimates were from published studies.
Measure of benefit:
Quality-adjusted life-years (QALYs) gained were the measure of benefit. Future benefits were discounted at an annual rate of 3.5%.
Cost data:
The direct costs included those of the exercise referral scheme and the annual treatment of coronary heart disease, stroke, and type II diabetes. Scheme costs included the provision of facilities (leisure facility use), exercise trainers, and administrative support. These costs were from studies identified by the 2011 systematic review and meta-analysis or UK published estimates. All costs were inflated to 2010 prices, using the consumer price index, and were reported in UK £. Future costs were discounted at an annual rate of 3.5%.
Analysis of uncertainty:
Deterministic sensitivity analyses (one-way, scenario, and extreme-value analyses) were undertaken to assess the impact of uncertainty on the results. A probabilistic sensitivity analysis was conducted to assess the uncertainty in key parameters varied together. Subgroup analyses were conducted for sedentary 40- to 60-years-olds, with a diagnosed condition known to benefit from physical activity (obesity, hypertension, or depression).