A Controlled Trial to Determine the Efficacy of Red and Near-Infrared Light Treatment in Patient Satisfaction, Reduction of Fine Lines, Wrinkles, Skin Roughness, and Intradermal Collagen Density Increase
Objective: The purpose of this study was to investigate the safety and efficacy of two novel light sources for large area and full body application, providing polychromatic, non-thermal photobiomodulation (PBM) for improving skin feeling and appearance.
Background data: For non-thermal photorejuvenation, laser and LED light sources have been demonstrated to be safe and effective. However, lasers and LEDs may offer some disadvantages because of dot-shaped (punctiform) emission characteristics and their narrow spectral bandwidths. Because the action spectra for tissue regeneration and repair consist of more than one wavelength, we investigated if it is favorable to apply a polychromatic spectrum covering a broader spectral region for skin rejuvenation and repair.
Materials and methods: A total of 136 volunteers participated in this prospective, randomized, and controlled study. Of these volunteers, 113 subjects randomly assigned into four treatment groups were treated twice a week with either 611–650 or 570–850 nm polychromatic light (normalized to ∼9 J/cm2 in the range of 611–650 nm) and were compared with controls (n=23). Irradiances and treatment durations varied in all treatment groups. The data collected at baseline and after 30 sessions included blinded evaluations of clinical photography, ultrasonographic collagen density measurements, computerized digital profilometry, and an assessment of patient satisfaction.
Results: The treated subjects experienced significantly improved skin complexion and skin feeling, profilometrically assessed skin roughness, and ultrasonographically measured collagen density. The blinded clinical evaluation of photographs confirmed significant improvement in the intervention groups compared with the control. Conclusions: Broadband polychromatic PBM showed no advantage over the red-light-only spectrum. However, both novel light sources that have not been previously used for PBM have demonstrated efficacy and safety for skin rejuvenation and intradermal collagen increase when compared with controls.
COMPLETE RESEARCH STUDY
Altering cellular function using low level, non-thermal LED light is called photobiomodulation (PBM) or low-level light therapy (LLLT), and is a medical treatment modality of increasing clinical importance. Because of the combination of high degree of penetration in skin and absorption by respiratory chain components, light in the spectral range from 600 to 1300 nm is useful for promoting wound healing, tissue repair, and skin rejuvenation. In contrast to traumatic ablative (e.g., laser resurfacing) and non-ablative (e.g., intense pulsed light [IPL]) skin rejuvenation modalities that induce secondary tissue repair by causing controlled damage to either the epidermis or the dermis, PBM is atraumatic, and bypasses the initial destructive step by directly stimulating regenerative processes in the skin. Its action mechanisms encompass increased cellular proliferation, migration, and adhesion. Important cell types for skin and tissue regeneration are fibroblasts, keratinocytes, and immune cells (mast cells, neutrophils, and macrophages), which can be stimulated using specific wavelengths with significant tissue penetration properties. The known severe side effects of traumatic skin rejuvenation procedures, such as inflammation, unpleasant pain perception, and prolonged social down time, are unknown in PBM; PBM has been successfully administered to reduce common symptoms of laser resurfacing and IPL treatment. Photon emitters, such as lasers or LEDs, have proven to be effective light sources for PBM during recent decades, thereby demonstrating that it is not the technical type of light source but the treatment parameters such as wavelength, irradiance, and fluence that are likely to be accountable for the effects. However, laser and LED light sources may offer some disadvantages because of their dot-shaped (punctiform) emission characteristics and narrow spectral bandwidths. Because the action spectra for tissue regeneration and repair consist of more than one wavelength, it might be favorable to apply a polychromatic spectrum covering a broader spectral region for skin rejuvenation and skin repair. We investigated the safety and efficacy of a novel non-thermal, non-ablative, atraumatic, polychromatic low-level light treatment modality with a focus on pleasant skin feeling, improved skin appearance, intradermal collagen increase, and the visible reduction of fine lines and wrinkles in a prospective, randomized, controlled trial that consisted of 136 volunteers.
The subjects were between 27 and 79 years of age. Inclusion criteria were the capacity to independently position oneself to use the device, the capacity to understand the treatment, a signed declaration of consent, and interest in continuous participation. The exclusion criteria were physical and psychological disease casting doubt on the capacity to consent, preliminary treatment with red light within the 6 months prior to the beginning of the study, recent invasive cosmetic procedures such as Botox during the 12 months prior to the beginning of the study, acute or prior skin cancer, acute skin disease requiring dermatological treatment, existing or planned pregnancy, lactation, history of photosensitivity or recent use of photosensitizing medication, epilepsy, and the tendency to faint. All of the participants gave written informed consent for this study, which was approved by the Ethics Committee of the Medical Association (Landesärztekammer) Baden-Württemberg, Stuttgart, Germany. The investigation was conducted in accordance with the Declaration of Helsinki (DoH/Oct2008). After the declaration of informed consent following examination of the inclusion and exclusion criteria, each participant was assigned to one of four groups using a computerized randomization process. Group 5 was mainly recruited from employees of the JK company without randomization, and served as the control. Groups 1–4 were treated twice a week with 30 treatments in total, starting in January 2012. To minimize the influence of seasonal changes, the time interval for data acquisition at the baseline, t15, t30, and follow-up examinations was restricted to 1 month. The data acquisition at baseline was completed in February 2012, and all of the volunteers finished treatment 30 (t30) in June 2012.
The control group did not receive any treatment, as the therapy cannot be blinded, and a sham light source without any effect most likely does not exist. The control group volunteers participated in the clinical measurements only, and the acquisition of subjective parameters such as skin feeling and skin complexion was not conducted. Because of the similar spectral lamp characteristics for groups 1 and 2 and groups 3 and 4, groups 1 and 2 were combined for evaluation as the “mid-pressure lamp group” [energizing light technology (ELT)], and groups 3 and 4 were evaluated together as the “low-pressure lamp group” [red light technology (RLT)] to obtain larger group sizes and, therefore, higher statistical power. Nevertheless, the subdivision into groups 1–4 allowed us to compare outcomes based on different treatment parameters, such as spectral distribution, irradiance, and fluence. A questionnaire concerning the tolerability of the application was filled in after each treatment (t1–t30). Digital photographs and clinical measurements were taken, and subjective questionnaires were used to assess complexion and skin feeling at the baseline (t0) and after 15 (t15) and 30 treatments (t30). The follow-up acquisition of subjective and clinical parameters was conducted at t30+6 months.
Treatment units 2, 3, and 4 provided full-body irradiation, covering the ventral and dorsal surfaces of the head, neck, trunk, upper limbs, and lower limbs at the same time. Full-body irradiation units 2 and 3 enabled treatment with the patient in a horizontal, reclined position, whereas unit 4 was engineered as a cabin for vertical treatment orientation. Unit 1 was designed for the local treatment of the face and décolletage area with the patient sitting in a chair in a semi-reclined position. Units 1 and 2 were equipped with medium-pressure gas discharge lamps in combination with spectrally selective reflectors and corresponding filter systems, to eliminate spectral emissions in wavelengths <570 and >850 nm; these units were denoted as ELT. Units 3 and 4 were equipped with low-pressure gas discharge fluorescent lamp tubes providing a spectral emission peak predominantly within the range of 611–650 nm, denoted as RLT. Because of the different spectral properties and irradiances, we defined the spectral range between 611 and 650 nm for the calculation of treatment fluences. This wavelength window encompasses 632.8 nm, which is a paramount wavelength in LLLT and PBM, representing the dominant wavelength of a HeNe-laser. The spectral dose distributions of the ELT and RLT light sources are shown in, with the doses of both light sources normalized to 100 % for the 611–650 nm range. The treatment doses were kept constant for this spectral range, whereas irradiances and treatment durations varied for all four treatment groups in order to investigate the applicability of the Bunsen–Roscoe law of reciprocity within the given parametrical limits.
Patient characteristics
Initially, 144 volunteers were recruited for the trial. Eight volunteers did not appear for the first appointment after randomization; therefore, the total number of patients finally included in the study was 136. Five volunteers stopped participating because of schedule incompatibilities and lack of time. One volunteer could not finish the treatment because of receiving antibiotic medication, which was one of the exclusion criteria; one volunteer terminated participation because of moving away; and one participant missed more than four treatments because of a period of residence at a health resort. Ultimately, 128 volunteers completed the treatment and the follow-up evaluation course, of whom 57 were treated with RLT, 48 were treated with ELT, and 23 were controls. The volunteers in the RLT and ELT groups were similar with respect to age, weight, skin complexion, skin feeling, skin roughness, and intradermal collagen density. The percentage of women was lower in the ELT group than in the RLT group. The controls had a slightly higher mean collagen density and a lower mean skin roughness.
Adverse events
None of the volunteers dropped out because of an adverse event. No severe adverse events were registered during the study or the follow-up phase. One volunteer with facial telangiectasia noticed an increased visibility after the first treatments, and decided to protect the zones in question from the light influence using a concealer for the rest of the treatment series. One volunteer experienced a reddening of scar tissue from a 40-year-old knee injury that was likely reactivated by the ELT 30 treatment. The affected scar healed completely within 1 week, and the treatments were continued without interruption.
Discussion
The use of LED light sources with 590, 633, and 830 nm wavelengths for athermal light-only photorejuvenation has grown rapidly in recent years. Additional wavelengths have been shown to be efficient in altering cellular functions, such as 570, 620, 680, 760, and 820 nm. The treatment doses vary significantly, ranging from 0.1 J/cm2 for 590 nm LED light with a specific sequence of pulsing, up to 126 J/cm2 for 633 nm continuous LED light. The power of the light typically ranges between 1 and 1000 mW, depending upon the type of light source and the application. Efficacy comparisons of the different devices available to the physician are not known to the authors.
This study is the first prospective clinical trial investigating the safety and efficacy of novel light sources for skin rejuvenation and the stimulation of dermal collagen synthesis based on low-pressure and mid-pressure gas discharge lamps. These light sources, in contrast to lasers and LEDs, allow simultaneous treatment with a tailored spectrum composed of several spectral bands that are effective in PBM. When compared with the initial values and the controls, the volunteers experienced significant improvements in their personal assessments of skin feeling and complexion, in clinical outcomes as assessed by collagen density and skin roughness measurements and in the reduction of fine lines and wrinkles as assessed by three blinded evaluators comparing t0 and t30 photographs.
Previous findings were able to correlate fibroblast activity and dermal matrix remodeling processes, with an increase in intradermal collagen density and reduced signs of aging. The proposed underlying mechanisms include the photostimulation of terminal molecules in the electron transport chain and the subsequent adenosine triphosphate (ATP) concentration increase, along with the selective light-driven activation of water molecules, thereby enhancing metabolic exchange and influencing the ion transporter systems found in cellular membranes. Detailed analysis of the gene expression profiles in human fibroblasts revealed an influence of low-intensity red light with a 628-nm wavelength on 111 different genes that are involved in cellular functions, such as cell proliferation; apoptosis; stress response; protein, lipid and carbohydrate metabolism; mitochondrial energy metabolism; DNA synthesis and repair; antioxidant related functions; and cytoskeleton- and cell-cell interaction-related functions. A specific role of reactive oxygen species (ROS) in increasing fibroblast proliferation and motility has recently been reported, suggesting that the elevation of ROS via photodynamic therapy can enhance the cellular functions of dermal fibroblasts through specific mitogen-activated protein kinase (MAPK) signaling pathways in vitro. The light-induced free radical formation in human skin has been investigated in detail, demonstrating that red light with 620 and 670 nm wavelengths increases the concentration of ROS even without the influence of external photosensitizers.
Because fibroblasts are responsible for collagen production in wound healing, dermal remodeling, and tissue repair, we decided to focus on increased collagen density as a surrogate marker for fibroblast activity, and abandoned such invasive monitoring methods as histologic examinations following skin biopsies for our study.
Ultrasonographic collagen assessment is described as a feasible noninvasive methodology for monitoring dermal density during the senescence process.
A report of the stimulatory effects of 660 nm wavelength laser light on scar fibroblasts could conceivably explain the potential reactivation of a>40-year-old knee injury, which occurred in one volunteer during the ELT treatment. Therefore, the influence of PBM on scar tissue should be subject to further investigation.
Some authors emphasize the importance of distinct wavelengths for optimal results. In our study, the differences between the RLT and ELT treatments in clinical outcome and patient satisfaction were not significant, indicating that despite spectral differences, both light sources were commensurably effective regarding study objectives. Further studies of the treatment parameters are necessary.
The evaluation of clinical photography revealed a particular worsening of fine lines and wrinkles from t0 to t30 in the control group, which was not expected for a course of only 12 weeks. A possible explanation could be the seasonal variation of skin condition between winter and summer climates and the influence of solar radiation, as the clinical photography revealed skin pigmentation as a consequence of exposure to sunlight.
We observed a tendency that ELT/RLT treatment led to better results in female volunteers regarding the collagen density increase. This gender-specific response could conceivably be explained by physiological differences between male and female skin on endocrine and extracellular matrix levels. However, gender-specific differences should be evaluated in greater detail in further investigations.
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