Background: Female pattern hair loss, or androgenic alopecia, is the most common type of hair loss affecting women. It is characterised by progressive shortening of the duration of the growth phase of the hair with successive hair cycles, and progressive follicular miniaturisation with conversion of terminal to vellus hair follicles (terminal hairs are thicker and longer, while vellus hairs are soft, fine, and short). The frontal hair line may or may not be preserved. Hair loss can have a serious psychological impact on people.
Objectives: To determine the effectiveness and safety of the available options for the treatment of female pattern hair loss in women.
Search methods: We searched the following databases up to October 2011: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library (2011, Issue 4), MEDLINE (from 1946), EMBASE (from 1974), PsycINFO (from 1806), AMED (from 1985), LILACS (from 1982), PubMed (from 1947), Web of Science (from 1945), and reference lists of articles. We also searched several online trials registries for ongoing trials.
Selection criteria: Randomised controlled trials that assessed the effectiveness of interventions for female pattern hair loss in women.
Data collection and analysis: Two review authors independently assessed trial quality and extracted data.
Main results: Twenty two trials, comprising 2349 participants, were included. A wide range of interventions were evaluated, with 10 studies investigating the different concentrations of minoxidil. Pooled data from 4 studies indicated that a greater proportion of participants (121/488) treated with minoxidil reported a moderate increase in their hair regrowth when compared with placebo (64/476) (risk ratio (RR) = 1.86, 95% confidence interval (CI) 1.42 to 2.43). In 7 studies, there was an important increase of 13.28 in total hair count per cm(2) in the minoxidil group compared to the placebo group (95% CI 10.89 to 15.68). There was no difference in the number of adverse events in the twice daily minoxidil and placebo intervention groups, with the exception of a reported increase of adverse events (additional hair growth on areas other than the scalp) with minoxidil (5%) twice daily. Most of the other comparisons consisted of single studies. These were assessed as high risk of bias: They did not address our prespecified outcomes and provided limited evidence of either the efficacy or safety of these interventions.
Authors' conclusions: Although more than half of the included studies were assessed as being at high risk of bias, and the rest at unclear, there was evidence to support the effectiveness and safety of topical minoxidil in the treatment of female pattern hair loss. Further direct comparison studies of minoxidil 5% applied once a day, which could improve adherence when compared to minoxidil 2% twice daily, are still required. Consideration should also be given to conducting additional well-designed, adequately-powered randomised controlled trials investigating several of the other treatment options.