BACKGROUND: Long-term gender-affirming hormone therapy (GHT) in older transgender individuals could have beneficial effects on cognitive functioning. Cardiovascular risk factors and psychological factors are known determinants of cognition. Despite the rising number of older transgender individuals, only few studies have examined cognitive functioning in this population. AIM: We aimed to assess differences in cognitive functioning between transgender women, and non-transgender (cisgender) women and men, and investigated the contribution of cardiovascular risk factors and psychological factors on these differences. METHODS: In this study, 37 transgender women (age range 55 to 69) receiving GHT for at least ten years (range 10.2 to 41.6) were examined, and their cognitive functioning was compared to an age and education level matched cohort consisting of 222 cisgender women and men from the Longitudinal Aging Study Amsterdam. Linear regression analyses were performed. OUTCOMES: Cognitive functioning was assessed by neuropsychological tests including Mini-Mental State Examination (MMSE), Category Fluency animals, Letter Fluency D, 15-Word test (15WT) immediate and delayed recall. Additionally, cardiovascular risk factors and psychological factors such as cardiovascular disease, hypertension, antihypertensive use, statin use, diabetes mellitus, overweight, smoking, alcohol consumption, psychopharmaceutical use, anxiety and depression symptoms were collected. RESULTS: Transgender women had higher MMSE scores compared with cisgender women (+0.9, 95% CI 0.4 to 1.5), and cisgender men (+1.1, 95% CI 0.4 to 1.8). On all other tests transgender women performed similar to cisgender men. Transgender women performed at a lower level than cisgender women on 15WT immediate recall, -5.5, 95% CI -7.6 to -3.4, and 15WT delayed recall, -2.7, 95% CI -3.7 to -1.7, and equal to cisgender women on Fluency animals and Fluency D. Cardiovascular and psychological factors (i.e., cardiovascular disease and depression symptoms) partly explained differences on MMSE score between transgender women and cisgender-control groups. CLINICAL IMPLICATIONS: The results of this study do not indicate a need for tailored hormone treatment strategies for older transgender women, based on cognitive aspects after long-term GHT. STRENGTHS & LIMITATIONS: As one of the first studies, this study compared older transgender women to a large cohort of cisgender men and women regarding cognitive functioning and took into account numerous potential influencing factors. Limitations include difference in test procedures and the cross-sectional design of the study. CONCLUSION: Cognitive differences between transgender women and cisgender women and men were small, albeit significant. This may suggest that long-term GHT effects on cognitive functioning in older transgender women are minimal. van Heesewijk JO, Dreijerink KMA, Wiepjes CM, et al. Long-Term Gender-Affirming Hormone Therapy and Cognitive Functioning in Older Transgender Women Compared With Cisgender Women and Men. J Sex Med 2021;18:1434-1443.