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 Incre

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/cm 2 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.

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. 1 Because of the combination of high degree of penetration in skin 2 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. 3–5 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. 6 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. 7 The known severe side effects of traumatic skin rejuvenation procedures, such as inflammation, unpleasant pain perception, and prolonged social down time, 8 are unknown in PBM; PBM has been successfully administered to reduce common symptoms of laser resurfacing and IPL treatment. 9 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. 10 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, 7 , 11 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.

Materials and Methods

Study population and design

We conducted a randomized, controlled clinical trial between January 2012 and December 2012. summarizes the baseline (t0) characteristics of the subject groups.

Table

1.

 RLT (n=57)ELT (n=48)Controls (n=23)Sex Female49/86.0%34/70.8%15/65.2% Male8/14.0%14/29.2%8/34.8%Agea46.2±9.048.6±9.844.4±10.2Weighta72.9±15.2273.4±13.773.7±13.4Skin complexion (subjective)b4.54±1.924.87±2.02 Skin feeling (subjective)b5.33±2.045.24±2.18 Skin roughness (Ra)b15.29±4.2014.84±4.0411.79±2.17Collagen intensity scorec20.40±6.5518.96±3.5423.22±7.36Expert wrinkle assessmentd No/shallow or fine wrinkles14/24.6%17/35.4%5/21.7% Moderate wrinkles20/35.1%11/22.9%6/26.1% Prominent or deep wrinkles13/22.8%11/22.9%9/39.1% No majority vote possible10/17.5%9/18.8%3/13.0%Open in a separate window

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.

Light Sources

Four units equipped with two different types of polychromatic light sources (low-pressure vs. mid-pressure lamps) were used to conduct this study. lists the lamp technologies, lamp types, treatment area (full or part of the body), spectral values, session duration, and treatment doses for the units used in this study.

Table

2.

 Treatment units (groups 1 – 4) ELT 2ELT 30C 46 sunCVT/RVTTechnologyEnergizing light (ELT)Energizing light (ELT)Red light (RLT)Red light (RLT)Lamp typeMedium pressureMedium pressureLow pressureLow pressureTreatment areaPartial-bodyFull-bodyFull-bodyFull-bodyTreatment positionSemi-reclinedHorizontalHorizontalVerticalIrradiance (611–650 nm)7.1 mW/cm210.4 mW/cm25.9 mW/cm213.3 mW/cm2Total irradiance (570–850 nm)42.8 mW/cm254.8 mW/cm210.3 mW/cm223.4 mW/cm2Treatment duration20 min15 min25 min12 minTreatment dose (611–650 nm)8.5 J/cm29.4 J/cm28.9 J/cm29.6 J/cm2Total radiant exposure (570–850 nm)51.4 J/cm249.3 J/cm215.5 J/cm216.8 J/cm2Open in a separate window

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.

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All units emitted almost no erythemogenic UV radiation (minimal erythema dose would not be reached after several hours of exposure, comparable to the UV emission of fluorescent lamps for general lighting service applications).

Measurements

The primary objective of the study was the improvement of subjective skin complexion and skin feeling. The volunteers were asked to specify their level of agreement to the statements in the questionnaire by marking a position along a continuous black line between two end points measuring 10 cm, which served as a visual analog scale (VAS). The secondary objectives were the improvement of measurement parameters using a DermaLab Combo (Cortex Technology, Hadsund, Denmark), a computer-supported skin diagnostics system equipped with a rotating high-resolution ultrasound sensor probe (20 MHz) for the determination of changes in intradermal collagen density, measured as a collagen intensity score (CIS). A Primoslite digital fringe projection system (GFM Messtechnik, Berlin, Germany) was used to measure the objective arithmetical roughness (Ra) of the skin surface in the periorbital region.

Photography

The digital photographs for the blinded wrinkle assessment were taken using a Nikon D5100 camera equipped with a Nikkor AF 50 mm 1:1.4 lens (Nikon Corporation, Chiyoda, Tokyo, Japan) and a Walimex RFL-3 ring light (Walser GmbH & Co. KG, Burgheim, Germany).

Subject outcome assessment

The subjective efficacy parameters were self-assessed at the baseline (t0), after 15 (t15) and 30 (t30) treatments, and after t30+6 months using 10 cm VAS for the improvements in skin complexion and skin feeling. These parameters were not assessed in the control group.

Objective clinical parameter assessment

The high-resolution ultrasound examination of collagen has enabled the measurement of visible changes in collagen density and numerical CISs representing the intradermal collagen fiber density. Profilometry yielded a numerical value for the Ra of the skin area under examination.

Investigator assessment

Three independent physicians who were blinded to the clinical patient data, analyzed the clinical photographs obtained at t0 and t30. The investigators were instructed to arrange the randomly assorted sets of clinical photographs taken at t0 and t30 into a before/after treatment sequence. The baseline wrinkle depth according to the Modified Fitzpatrick Wrinkle Scale (MFWS)12 and the degree of wrinkle reduction after treatment had to be assessed after sequencing. The votes of the investigators were summarized by the following majority rules: if two or three experts voted the same way, the agreed-upon classification was the summary measure; if all three experts voted differently, “no change” was the summary measure.

Statistical methods

The data in the tables are given as means±standard deviations. Comparisons of the changes in skin feeling, skin complexion, roughness, and collagen intensity from the baseline to t30 between the different treatment groups (intergroup comparisons) were performed using a linear model, with the baseline value of each volunteer as a covariate. Within-group differences from the baseline to values at t30 were assessed using the Mann–Whitney–Wilcoxon test. To compare wrinkle difference assessments among groups, we used the χ2 test. Within groups, we tested the hypothesis of equal probabilities of improvement and worsening using binomial tests. All tests were two sided, and p values<0.05 were considered statistically significant.