Speech therapy for transgender women: an updated systematic review and meta-analysis

BACKGROUND: We systematically reviewed the literature and performed a meta-analysis on the effects of speech therapy and phonosurgery, for transgender women, in relation to the fundamental frequency gain of the voice, regarding the type of vocal sample collected, and we compared the effectiveness of the treatments. In addition, the study design, year, country, types of techniques used, total therapy time, and vocal assessment protocols were analyzed. METHODS: We searched the PubMed, Lilacs, and SciELO databases for observational studies and clinical trials, published in English, Portuguese, or Spanish, between January 2010 and January 2023. The selection of studies was carried out according to Prisma 2020. The quality of selected studies was assessed using the Newcastle–Ottawa scale. RESULTS: Of 493 studies, 31 were deemed potentially eligible and retrieved for full-text review and 16 were included in the systematic review and meta-analysis. Six studies performed speech therapy and ten studies phonosurgery. The speech therapy time did not influence the post-treatment gain in voice fundamental frequency (p = 0.6254). The type of sample collected significantly influenced the post-treatment voice frequency gain (p < 0.01). When the vocal sample was collected through vowel (p < 0.01) and reading (p < 0.01), the gain was significantly more heterogeneous between the different types of treatment. Phonosurgery is significantly more effective in terms of fundamental frequency gain compared to speech therapy alone, regardless of the type of sample collected (p < 0.01). The average gain of fundamental frequency after speech therapy, in the /a/ vowel sample, was 27 Hz, 39.05 Hz in reading, and 25.42 Hz in spontaneous speech. In phonosurgery, there was a gain of 71.68 Hz for the vowel /a/, 41.07 Hz in reading, and 39.09 Hz in spontaneous speech. The study with the highest gain (110 Hz) collected vowels, and the study with the lowest gain (15 Hz), spontaneous speech. The major of the included studies received a score between 4 and 8 on the Newcastle–Ottawa Scale. CONCLUSION: The type of vocal sample collected influences the gain result of the fundamental frequency after treatment. Speech therapy and phonosurgery increased the fundamental frequency and improved female voice perception and vocal satisfaction. However, phonosurgery yielded a greater fundamental frequency gain in the different samples collected. The study protocol was registered at Prospero (CRD42017078446). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13643-023-02267-5.