Purpose: Sexual minority adults experience considerable mental and physical health disparities compared to their heterosexual counterparts, but changes in these disparities over time may, in part, reflect changes in how the same people self-identify their sexual orientation. Therefore, we estimated between-cohort and within-person changes in self-identified sexual orientation to better understand changes in sexual orientation-based health disparities over the life course. Methods: We examined 2009 to 2015 changes among 5712 adults 19-25 years of age from the Longitudinal Study of Young People in England (LSYPE) to validate a synthetic cohort approach applied to cross-sectional data on 1,168,346 adults 18-74 years of age (n = 29,677 sexual minority adults) from the General Practice Patient Survey (GPPS), estimating 2009 to 2017 changes in sexual orientation identification. Results: Heterosexual identification for adults 18-24 years of age fell three percentage points from 2009 to 2017. Approximately half of those 26-32 years of age, who identified as sexual minority adults in 2017, may not have identified as such 8 years earlier. LSYPE and GPPS results were similar, validating the synthetic cohort application. Within-cohort analyses estimated that 2.1% and 2.7% of heterosexual-identified women and men 18-24 years of age in 2009, respectively, changed identification by 2017. Smaller changes occurred for adults 25-34 years of age (1.0% and 1.2%, respectively), with still smaller differences at older ages. Conclusion: Changes in health disparities may reflect people newly identifying as a sexual minority as well as longitudinal changes in those long identifying as sexual minority adults. Future research should measure the health of both early- and late-identifying sexual minority adults, as their health care and policy needs may differ.
Keywords: General Patient Practice Survey; Longitudinal Study of Young People in England; health disparities; longitudinal data; sexual orientation; synthetic cohort.