Effect of heated mittens on physical hand function in people with hand osteoarthritis: randomised controlled trial

OBJECTIVE: To assess the effect of electrically heated mittens on physical hand function in people with osteoarthritis of the hands compared with control mittens. DESIGN: Randomised controlled trial. SETTING: Osteoarthritis outpatient clinic, Copenhagen, Denmark. PARTICIPANTS: 200 people with hand osteoarthritis aged 42-90 years. 100 participants were assigned to the intervention group and 100 to the control group. INTERVENTIONS: Electrically heated mittens or control mittens (heating elements disconnected) worn for at least 15 minutes daily for six weeks. MAIN OUTCOME MEASURES: The primary outcome was change in hand function measured on the function subscale of the Australian/Canadian hand osteoarthritis index (AUSCAN; score 0-100 points) at six weeks. Key secondary outcomes included changes in the AUSCAN hand pain subscale (score 0-100 points), global rating of hand osteoarthritis related problems (0-100 visual analogue scale), and grip strength (newtons) at six weeks. Analysis of secondary outcomes was performed using a hierarchical gatekeeping approach. RESULTS: 91 participants in the intervention group and 95 in the control group completed the trial. The mean age of participants was 71 years, 87% (n=173) were women, and mean body mass index was 24.9 (SD 4.4). Median disease duration was 10 years (interquartile range 5-15 years). The between group difference for change in AUSCAN function at week 6 was 3.0 points (95% confidence interval (CI) -0.4 to 6.3; P=0.09) in favour of heated mittens. For the key secondary outcome, change in AUSCAN hand pain score from baseline, a group difference was observed of 5.9 points (95% CI 2.2 to 9.5) in favour of heated mittens. Changes in global rating of hand osteoarthritis related problems and grip strength did not differ between the groups with an observed difference between groups of 2.8 points (95% CI -3.7 to 9.2) and 2.3 newtons (95% CI -16.3 to 21.0) in favour of heated mittens, respectively. CONCLUSION: Use of electrically heated mittens for six weeks was not related to a positive change in physical hand function compared with control mittens. Heated mittens provided no additional benefits on global rating of hand osteoarthritis related problems and grip strength. A small benefit was detected for hand pain, but this could have been overestimated. TRIAL REGISTRATION: ClinicalTrials.gov NCT04576403.