A Closer Look At The Research Behind MIRE Therapy
Monochromatic infrared light energy (MIRE) therapy is controversial. Do you prescribe this therapy? How can infrared light reverse sensory neuropathy or heal ulcers? Some reports indicate that just two weeks of therapy is enough to show significant improvement. Some patients rave about its benefits. Patients may say they no longer have numbness and/or pain. They may say they sleep better. It sounds too good to be true.
Aside from the anecdotal claims, here are just a handful of published studies that have been used to evaluate MIRE therapy to improve sensory neuropathy, painful neuropathy and wound healing. There are four retrospective, two prospective cohort studies and three randomized clinical trials that have evaluated the effect of this therapy on peripheral sensory neuropathy among people with diabetes.1-9
However, a closer review of these studies reveals that bias, limitations in study design and errors in statistical analysis have lead to important errors in the interpretation of the study data and the authors’ conclusions.
The three randomized clinical trials (RCTs) that evaluate changes in diabetic sensory neuropathy with active and sham monochromatic infrared light therapy offer the highest level of clinical evidence currently available. All three of these trials randomize one extremity to receive active therapy and one extremity to receive sham therapy. The study authors evaluate people with diabetes with various levels of sensory neuropathy. Semmes-Weinstein monofilaments (SWM) are the primary tool the researchers used to evaluate neuropathy in all three studies although they utilized other objective and subjective tools as well.
The clinical trials by Leonard and Arnall report statistically significant improvement in limbs treated with active MIRE therapy based on “changes” in Semmes-Weinstein monofilament testing.7,8 However, Clifft and colleagues did not identify any improvement after therapy in any of the test parameters.9
When it comes to research, clinicians tend to be the least comfortable with statistical analysis so we tend to believe what we are told. However, statistical analysis and design issues are often the crux of critical appraisal. Several of the fatal flaws in the published MIRE clinical trials involve errors in analysis. Some of the basic analytic errors in Leonard and Arnall’s trials contributed to misinterpretation of the data and reporting the wrong conclusion.7,8 In these studies, researchers used inappropriate statistical tests and they failed to compare active and sham treatment results at the end of both studies. Leonard’s study did not use an “intent to treat” analysis.7
What About The Flaws In Study Design And Analysis?
One of the most interesting aspects of the studies that evaluate MIRE is the consistent and often large placebo effect. There is an improvement in SWM testing in the sham group in all three randomized clinical trials. The strong placebo effect is probably the reason the uncontrolled retrospective and prospective studies had positive results.1-6 In Leonard’s study, there is such a strong placebo effect that when one compares pre- and post- intragroup comparisons, the Michigan Neuropathy Screening Questionnaire shows a significant change in active and sham treatment groups.7 Arnall’s study reports as much as a 70 percent improvement in SWM results in the sham treatment group.8
Both Leonard and Arnall only compared pre- and post-therapy results within the active or within the sham groups.7,8 There was no analysis that compared outcomes between treatment groups. Since there was such a large placebo effect in the sham treatment group, there is not a significant difference between active and sham therapy at the end of the studies. For instance, in the Leonard study, researchers correctly identified 2.4 out of five SWM sites in the active group and 3.0 out of five sites in the sham group.7