Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials

The purpose of this review is to explore the effectiveness of low-level laser therapy (LLLT) in the treatment of adult androgenic alopecia (AGA). A systematic search of studies on LLLT for AGA was conducted mainly in Pubmed, Embase, and Cochrane Systematic Reviews. The standardized mean difference (SMD) in the changes of hair density treated by LLLT versus sham devices was analyzed. The meta-analysis included 8 studies comprising a total of 11 double-blinded randomized controlled trials. The quantitative analysis showed a significant increase in hair density for those treated by LLLT versus sham group (SMD 1.316, 95% confidence interval, CI 0.993 to 1.639). The subgroup analysis demonstrated that LLLT increases hair growth in both genders, in both comb- and helmet-type devices, and in short- and long-term treatment course. The subgroup analysis also showed a more significant increase of hair growth for the LLLT versus sham in the low-frequency treatment group (SMD 1.555, 95% CI 1.132 to 1.978) than in the high-frequency group (SMD 0.949, 95% CI 0.644 to 1.253). The review was limited by the heterogeneity of included trials. LLLT significantly increased hair density in AGA. The meta-analysis suggests that low treatment frequency by LLLT have a better hair growth effect than high treatment frequency. LLLT represents a potentially effective treatment for AGA in both male and female. The types of LLLT devices and LLLT treatment course duration did not affect the effectiveness in hair growth.