Cost-effectiveness of strength exercise or aerobic exercise compared with usual care for patients with knee osteoarthritis: secondary results from a multiarm randomised controlled trial in Norway

Abstract

Objectives: To evaluate the 1-year cost-effectiveness of strength exercise or aerobic exercise compared with usual care for patients with symptomatic knee osteoarthritis (OA), from a societal and healthcare perspective.

Design: Cost-effectiveness analysis embedded in a three-arm randomised controlled trial.

Participants and setting: A total of 161 people with symptomatic knee OA seeking Norwegian primary or secondary care were included in the analyses.

Interventions: Participants were randomised to either 12 weeks of strength exercise (n=54), 12 weeks of aerobic exercise (n=53) or usual care (n=54).

Outcome measures: Quality-adjusted life-years (QALYs) estimated by the EuroQol-5 Dimensions-5 Levels, and costs related to healthcare utilisation and productivity loss estimated in euros (€), aggregated for 1 year of follow-up. Cost-effectiveness was expressed with mean incremental cost-effectiveness ratios (ICERs). Bootstrapping was used to estimate ICER uncertainty.

Results: From a 1-year societal perspective, the mean cost per patient was €7954, €8101 and €17 398 in the strength exercise, aerobic exercise and usual care group, respectively. From a 1-year healthcare perspective, the mean cost per patient was €848, €2003 and €1654 in the strength exercise, aerobic exercise and usual care group, respectively. Mean differences in costs significantly favoured strength exercise and aerobic exercise from a 1-year societal perspective and strength exercise from a 1-year healthcare perspective. There were no significant differences in mean QALYs between groups. From a 1-year societal perspective, at a willingness-to-pay threshold of €27 500, the probability of strength exercise or aerobic exercise being cost-effective was ≥98%. From a 1-year healthcare perspective, the probability of strength exercise or aerobic exercise being cost-effective was ≥97% and ≥76%, respectively.

Conclusion: From a 1-year societal and healthcare perspective, a 12-week strength exercise or aerobic exercise programme is cost-effective compared with usual care in patients with symptomatic knee OA.

Trial registration number: NCT01682980.

Keywords: health economics; physical therapy modalities; primary health care.

Figure 1. Cost-effectiveness plane and cost-effectiveness acceptability curve for different ceiling ratios (EUR) for quality-adjusted life-years (QALYs) indicating the probability of cost-effectiveness of strength exercise or aerobic exercise vs usual care on total costs (healthcare utilisation and productivity loss) and healthcare utilisation costs at 0–12 months. All estimates are based on bootstrapping (10 000 replicated datasets). The dashed line represents the willingness to pay (WTP) threshold of €27 500. EUR, euros.

Figure 2. Incremental cost-effectiveness ratio (ICER) tornado diagram for multiple one-way sensitivity analyses of (A) strength exercise (SE) versus usual care (UC) and (B) aerobic exercise (AE) versus usual care. The tail of each bar indicates the upper (light grey) and lower (dark grey) bound of the ICER when relevant costs/QALYs is varied 20% below and above estimates used in the main analysis (total costs, 0–12 months). The dashed line represents the willingness-to-pay (WTP) threshold to provide a reference for the ICERs. QALYs, quality-adjusted life-years.