medwireNews: A randomized controlled trial published in The BMJ has found that electrically heated mittens do not significantly improve physical hand function in people with hand osteoarthritis.
“Heat is recommended as treatment for hand osteoarthritis, and mittens may be a feasible means of delivering heat therapy. However, the results from this trial show that electrically heated mittens do not provide additional benefits for people with symptoms of hand osteoarthritis over standard mittens,” say Cecilie Bartholdy, from the Bispebjerg and Frederiksberg Hospital in Copenhagen, Denmark, and colleagues.
They enrolled 200 individuals (mean age 71 years; mean BMI 24.9 kg/m2; 87% women) with hand osteoarthritis (median disease duration 10 years) between October 2020 and January 2023. The participants were required to have an Australian/Canadian hand osteoarthritis index (AUSCAN) function subscale score of at least 40 points, indicating impaired hand function.
The patients were randomly assigned to wear either heated mittens or control mittens – with disconnected heating elements – for at least 15 minutes daily over 6 weeks during the coldest months (October to April). To assess masking, participants were asked to guess their group allocation at 2, 4, and 6 weeks.
In all, 91 participants in the intervention group and 95 in the control group completed the trial and at 6 weeks both groups demonstrated improvements in AUSCAN functional subscale scores, with respective least squares mean reductions of 6.3 and 3.3 points. However, the mean between-group difference in function was only 3.0 points, indicating no statistically significant benefit with heated mittens.
Heated mittens were associated with a significantly greater reduction at 6 weeks in the secondary endpoint of AUSCAN pain (least squares mean of 8.2 vs 2.3 points) compared with standard mittens, and numerically but not significantly greater reductions for AUSCAN stiffness (least squares mean of 9.3 vs 3.0 points) and the global rating of hand osteoarthritis-related problems (least squares mean of 3.2 vs 0.4 points), as measured on a visual analog scale from 0 to 100, where 0 indicates no problems.
However, Bartholdy et al note that due to masking being unsuccessful – by 6 weeks, 91% of study participants had correctly guessed their group allocation – “these observed differences should be interpreted with caution owing to the risk of the effect being overestimated.”
Unsuccessful masking could also explain why patients using heated mittens tended to wear them for longer, at a mean 11.9 mins/day, than those assigned standard mittens, they suggest, although mean daily wear time was 37 and 25 minutes, respectively, and therefore a “sufficient time to elicit a potential effect.”
After 6 weeks, 36% of participants in the intervention group and 46% in the control group reported stopping analgesics, a nonsignificant difference. And there were no significant differences between the two groups for the other secondary outcomes (symptoms, grip strength, tender and swollen joint counts). Only one adverse event (itching) was reported.
The researchers acknowledge that their target of an 8-point improvement in AUSCAN functional scores, set as the minimally important difference for improvement, was likely “overly ambitious,” and that the trial may have been underpowered to detect “small but potentially clinically relevant between group differences.”
Despite these limitations, Bartholdy and colleagues emphasize the high adherence to the protocol and the low incidence of adverse events, suggesting that heated mittens are a safe and feasible option for delivering heat therapy, but conclude that they do not provide additional benefits for physical hand function compared with control mittens.
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