Low level laser therapy

For more general use of lasers in therapy, see laser medicine. For more general use of light in therapy, see light therapy.

Low level laser therapy
Specialty	{{#statements:P1995}}
MeSH	D028022

Low-level laser (light) therapy (LLLT) is a form of laser medicine that uses low-level (low-power) lasers or light-emitting diodes (LEDs) to alter cellular function. Other names for the therapy include low-power laser, soft laser, cold laser, biostimulation laser, therapeutic laser, and laser acupuncture. Whereas high-power lasers ablate tissue, low-power lasers are claimed to stimulate it and to encourage the cells to function.

LLLT is integrated with mainstream medicine with ongoing research to determine where there is a demonstrable effect. Areas of dispute include the ideal location of treatment (specifically whether LLLT is more appropriately used over nerves versus joints), dose, wavelength, timing, pulsing and duration. The effects of LLLT appear to be limited to a specified set of wavelengths of laser, and administering LLLT below the dose range does not appear to be effective.

Medical uses

Despite a lack of consensus over its scientific validity, some recent meta-analyses and controlled studies of moderate quality suggest that LLLT might be effective for various medical indications such as

• breast-cancer related lymphedema
• hair loss
• hypothyroidism
• musculoskeletal pain.
• nonspecific chronic low-back pain
• oral mucositis
• shoulder tendinopathy
• wisdom tooth extraction (complications)

There is preliminary evidence for relieving chronic joint disorders, dentin hypersensitivity, labial herpes, neck pain, rheumatoid arthritis and temporomandibular disorders. The evidence for LLLT being useful in osteoarthritis, delayed-onset muscle soreness, orthodontic pain and wound healing is dubious. A Cochrane review found tentative evidence that low-level laser therapy may help in frozen shoulders.

Though it has been suggested for decades that LLLT could be useful in speeding wound healing, the appropriate parameters (dose, type of laser, materials, wavelength, etc.) have not been identified. Similarly, the use of lasers to treat chronic periodontitis and to speed healing of infections around dental implants is suggested, but there is insufficient evidence to indicate a use superior to traditional practices.

According to ClinicalTrials.gov database, LLLT is currently being studied in clinical trials for various treatment indications. In 2014, more than 400 scientific articles on LLLT were published.

Animal studies have been conducted to investigate the effectiveness of LLLT on various indications, e.g. allergic asthma, Alzheimer's disease, arthritis, atherosclerosis, colitis, diabetes, heart failure, laryngitis, liver regeneration, lung injury, multiple sclerosis, myocardial infarction, nerve injury, osteomyelitis and Parkinson's disease.

Stephen Barrett, writing for Quackwatch, concluded (2009) in there was evidence to support LLLT use for temporary pain relief, but "there's no reason to believe that they will influence the course of any ailment or are more effective than other forms of heat delivery." However, this sceptical viewpoint might be outdated since a notable amount of clinical LLLT research has been published after the year 2010.

Mechanism

The effects of LLLT are believed to be mediated by its effects on mitochondrial cytochrome c oxidase (Complex IV). The increased production of ATP and ROS, and the release of NO, lead to various changes in cellular function.

It is partially unclear how LLLT works. However, most of the scientific review articles suggest that specific wavelengths of the electromagnetic spectrum (600-1000 nm) might modulate the function of mitochondria by affecting the respiratory enzyme cytochrome c oxidase.

LLLT may reduce pain related to inflammation by lowering, in a dose-dependent manner, levels of pro-inflammatory prostaglandins and cytokines, the cellular influx of neutrophil granulocytes, oxidative stress, edema, and bleeding. The appropriate dose appears to be 0.3-19 J/cm2. Another mechanism may be related to stimulation of mitochondrion to increase the production of ATP resulting in an increase in reactive oxygen species, which influences redox signalling, affecting intracellular homeostasis or the proliferation of cells.

The effects of LLLT appear to be limited to a specified set of wavelengths of laser, and research is being conducted to determine the ideal wavelengths, treatment duration, dose and location of treatment. Administering LLLT below the dose range does not appear to be effective, but high doses also might be ineffective.

Treatment parameters such as effective dose, dose-rate effects, beam penetration, the role of coherence, and pulsing are still poorly understood in the clinical setting. The typical laser average power is in the range of 1-500 mW; some high-peak-power, short-pulse-width devices are in the range of 1-100 W with typical pulse-widths of 200 ns. The typical average beam irradiance then is 10 mW/cm² - 5 W/cm². The typical wavelength is in the range 600-1000 nm (red to near infrared), but some research has been done and products outside of this range are available.

History

In 1967 a few years after the first working laser was invented, Endre Mester in Semmelweis University in Budapest, Hungary experimented with the effects of lasers on skin cancer. While applying lasers to the backs of shaven mice, he noticed that the shaved hair grew back more quickly on the treated group than the untreated group.

Society and culture

The insurance company, Cigna, has reviewed (2010) the evidence for LLLT and concluded that it is still considered an experimental treatment. Therefore, Cigna does not provide coverage for it.

At least one LLLT practitioner, Robert Lytle DDS, has been cited by the FDA for promoting non-FDA approved treatments on company websites.

See also

• Photomedicine
• Light therapy
• Blood irradiation therapy