Provision of gender-affirming care for trans and gender-diverse adults: a systematic review of health and quality of life outcomes, values and preferences, and costs.

Background: There is a substantial evidence base documenting the impact of gender-affirming care on health outcomes among transgender (trans) and gender-diverse people globally, but this rapidly growing body of evidence has not been comprehensively synthesized. Methods: We conducted a systematic review of studies examining outcomes, values and preferences, and costs of gender-affirming care. Protocols were registered in PROSPERO (CRD42024539078 and CRD42024569628). We searched CINAHL, Cochrane Central, Embase, LILACS, PsycINFO, PubMed, and grey literature sources for studies published between 1 January 2018 and 31 March 2024. The outcomes review included data from randomized controlled trials and longitudinal studies that compared health outcomes among adults (age 18+) who received gender-affirming care to those who did not. We synthesized data by subtype (e.g. psychosocial, hormone therapy, surgical) and by study design, using GRADE evidence profiles. We assessed risk of bias with the Cochrane ROB2 and ROBINS-I tools. We summarized values and preferences data qualitatively and provided confidence ratings using GRADE CERQual, and narratively summarized cost data. Findings: Twenty-eight studies, including four randomized controlled trials and 24 longitudinal studies, evaluated health outcomes following gender-affirming care. Moderate to very low certainty evidence from these studies suggests gender-affirming care may improve quality of life, stigma, utilization of health services, and mental health. No studies identified significant negative outcomes or harms. An additional 87 values and preferences studies, six of which also provided cost data, found that gender-affirming care is acceptable and affordable, although costs vary by type of care. Interpretation: Gender-affirming care may improve critical outcomes, including quality of life, among trans and gender-diverse adults who seek this care. Additional data from prospective controlled studies would enhance the evidence base to comprehensively document the impact of gender-affirming care on physical and mental health outcomes. Funding: World Health Organization through a grant from the Elton John AIDS Foundation and the Bill and Melinda Gates Foundation.