Analytical approach:
The analysis was based on a single randomised controlled trial (RCT). The time horizon was one year. The authors stated that the perspective of both the UK National Health Service (NHS) and society were adopted.
Effectiveness data:
The clinical analysis was based on a recent UK-based RCT with a three-month follow-up period. The trial involved 39 general practices across England. Three hundred and thirteen consenting participants were randomised (156 in the yoga group; 157 in the usual care group). Patients were followed for up to 12 months. An intention-to-treat approach was used. The primary endpoint was the improvement of back function measured by Roland-Morris Disability Questionnaire (RMDQ) completed at three, six and 12 months post-randomisation.
Monetary benefit and utility valuations:
Utility valuations were assessed at follow-up points of three, six and 12 months post-randomisation during the trial using the EQ-5D questionnaire.
Measure of benefit:
Quality-adjusted life-years (QALYs) were used as the summary benefit measure.
Cost data:
Costs were estimated for the yoga intervention (teaching and equipment), visits to health care professionals (general practitioners, practice nurses, physiotherapists and other consultations), emergency services, hospital admissions, outpatient visits, private care, and productivity losses. Private care and productivity loss costs were excluded from the perspective of the NHS. Unit costs were based on official national tariffs, such as Personal Social Services Research Unit, and NHS reference costs. Costs of private care came from an insurance provider in the UK market. The average national income per day was used to estimate the cost of productivity losses. Quantities of resources used came from the RCT. Costs were in UK £ and referred to 2008/2009 prices.
Analysis of uncertainty:
Mean incremental costs and QALYs were estimated using a regression-based approach. Cost-effectiveness acceptability curves were constructed to investigate uncertainty on the cost-effectiveness of the two interventions at different willingness-to-pay thresholds. Sensitivity analyses were carried out to assess the impact of missing data in utility scores and costs, which were imputed using through multiple imputation. The impact of variations in yoga intervention costs was investigated. And finally, in an alternative scenario, the costs of travel and informal care were considered on the basis of evidence from another trial.