Properties of LED PBM studies analysed.

BackgroundThe advent of mass-market Light Emitting Diodes (LEDs) has seen considerable interest in potential dermatological applications of LED light photobiomodulation (PBM) for a range of conditions, with a thriving market for direct-to-consumer LED treatments, including red light, blue light, and yellow light wavelengths. Evidence of efficacy is however mixed, and studies report a wide range of irradiances and wavelengths as well as outcome measures, rendering interpretation, comparison, and even efficacy evaluation prohibitive and impeding evidence synthesis.MethodsThis work establishes a model for comparing patient received doses, applying this to existent studies to ascertain potential inhomogeneity in reported doses and wavelengths employed. Patient doses were contrasted to equivalent solar exposure time needed to achieve fluences reported at specified wavelengths in the red light (RL), blue light (BL), and yellow light (YL) portion of the spectrum, yielding a comparison of reported doses to typical solar irradiance at the Earth’s surface. Methodological aspects including dose validation, blinding, and bias were also analysed.Results27 relevant studies for dermatological conditions including acne vulgaris (, 33.3%), wrinkle-reduction (18.5%), wound-healing (, 11.1%), psoriasis severity (, 11.1%), and erythemal index (, 25.9%) were assessed. Outcome measures were highly heterogeneous between studies, with total patients ranging from 14 – 105 (median: 26). Fluences and wavelengths used in treatment differed over three orders of magnitude across studies even for the same conditions (, median: . Derived equivalent solar time ranged from 0.01-19.35 hours (median: 3.3 hours), with central wavelengths between 405nm (BL) - 660nm (RL). No studies reported any dose validation, 10 (37.0%) were sponsored by the device manufacturer with a further 3 (11.1%) conducted by commercial dermatology practices offering the therapy under investigation. Assessors were unblinded to the treatment/ control groups in 33.3% (), while a further 9 (33.3%) did not have any non-light control group, leaving only 33.3% ( with both control group and blinded outcome assessment.ConclusionsResults of this analysis suggest that fluences, wavelengths, and effective dose vary inconsistently between studies with often scant biological justification. This analysis suggests that better dose quantification and understanding of the underlying biophysics as well as plausible biological justifications for various wavelengths and fluences are imperative if LED therapy studies for dermatology are to be informative and research replicability improved.

### 背景
大众市场发光二极管（Light Emitting Diodes, LEDs）问世以来，LED光生物调节（Photobiomodulation, PBM）在多种皮肤病学适应症中的应用潜力受到广泛关注，面向消费者的LED治疗设备市场蓬勃发展，涵盖红光（RL）、蓝光（BL）与黄光（YL）波段。然而相关疗效证据存在分歧，现有研究报道的辐照度、波长以及结局指标差异巨大，使得疗效解读、对比乃至评估难以开展，同时阻碍了证据整合。

### 方法
本研究构建了一种用于对比患者接受剂量的模型，并将其应用于现有研究，以明确已报道的治疗剂量与所用波长存在的潜在异质性。将患者接受的剂量与达到特定光谱波段下报道的注量所需的等效太阳照射时长进行对比，从而将报道的剂量与地球表面典型太阳辐照度进行对标。本研究同时分析了剂量验证、设盲与偏倚等方法学维度。

### 结果
本研究共纳入27项针对皮肤病的相关研究，其中寻常痤疮（33.3%）、除皱（18.5%）、伤口愈合（11.1%）、银屑病严重程度评估（11.1%）以及红斑指数相关研究（25.9%）。各项研究的结局指标异质性显著，纳入患者总数为14至105例（中位数26例）。即便针对同一适应症，不同研究中所用治疗注量与波长的差异也跨越了三个数量级，推导得到的等效太阳照射时长范围为0.01至19.35小时（中位数3.3小时），中心波长覆盖405nm（蓝光）至660nm（红光）。未发现有研究报道剂量验证相关内容，其中10项（37.0%）由设备制造商资助，另有3项（11.1%）由提供所研究治疗方案的商业皮肤病诊所开展。33.3%的研究中评估者未对治疗组与对照组设盲，另有9项（33.3%）未设置非光照对照，最终仅33.3%的研究同时设置了对照组且对结局评估实施设盲。

### 结论
本次分析结果显示，不同研究间的注量、波长与有效剂量差异缺乏一致性，且多数情况下缺乏合理的生物学依据。本分析表明，若要让皮肤病学LED治疗研究具备临床参考价值并提升研究可重复性，亟需优化剂量量化方法、加深对相关生物物理学机制的理解，同时为不同波长与注量的应用提供合理的生物学解释。