Sexual minorities (SMs) are disproportionately vulnerable to a variety of poor health outcomes. In 2016, the National Institute on Minority Health and Health Disparities at the US National Institutes of Health formally recognized sexual and gender minorities as a population for health disparities research [1]. Sexual-orientation-related disparities span the spectrum of health outcomes, including physical health, mental health, and substance use [2–4]. Compared to heterosexual adults, for example, sexual minorities are 2–5 times as likely to have substance use disorders [5], 2 times as likely to indicate mood or anxiety disorders [6], and 2.5 times as likely to report lifetime suicide attempts [7]. A recent review documented greater cardiovascular disease risk among SM men and women [8], largely attributed to health conditions such as poor mental health and substance use. SM men are also at increased risk for both sexually transmitted infections (STI) and Human Immunodeficiency Virus (HIV) [2] and SM women are more likely to test positive for Hepatitis C [2].

A growing body of evidence suggests that sexual-orientation-related health disparities are largely driven by internal (e.g., internalized homophobia; expectations of rejection) and external (e.g., discrimination, victimization) stressors that uniquely impact sexual minorities across the life span -often referred to as minority stress [9–11]. Studies that utilize quasi-natural experimental designs, for example, highlight the deleterious effects of enacting anti-LGB policy for the health and well-being of SMs [12].There are, however, unique developmental considerations that must be taken into account when considering risk factors that contribute to the timing of sexual-orientation-related disparities. Schools, for example, are finite contexts that confer risk for victimization and bullying of SM youth [13], which can have lasting, but diminishing effects for mental health as adolescence age into adulthood [14]. SMs also have to navigate “coming out” – or disclosing their sexual identity to family and friends which is oftentimes stressful [15] – which may lead to rejection and consequent mental and behavioral health risk [16]. Despite evidence on the existence of sexual-orientation-related health disparities and the developmental nature of the associated risk factors, the progression of these health inequities across the lifespan is not completely understood.

Even with increased attention to SM health, significant research gaps remain [17]. Little is known, for example, about how health disparities [2,3,7] vary across the lifespan for sexual minorities, despite evidence that mental, behavioral, and physical health conditions vary in their onset and course over the life course [18–21]. Alcohol use disorder, for example, increases during late adolescence into young adulthood, peaks during the mid- twenties, and steadily declines across subsequent ages [21]. Considering that theoretical mechanisms of sexual orientation-related health disparities also vary by age [22], might the degree to which heterosexuals and SMs differ in these health-related outcomes change across the life course? Importantly, because there are developmental differences in the onset and prevalence of specific health conditions, researchers who aggregate data across broad age ranges (e.g., 18–65) may be over- or underestimating the degree to which SMs may be at risk for poor mental, behavioral, and physical health. Understanding how health conditions fluctuate across the lifespan would allow research efforts to more accurately examine developmentally-sensitive mechanisms that contribute to SMs’ increased vulnerability, and inform the development of tailored prevention and intervention strategies.

We hypothesize that health disparities between heterosexual and SM adults will vary by age, such that there are age ranges of greater vulnerability for specific health outcomes among SMs. To evaluate these hypotheses, we used nationally representative cross-sectional data and an innovative analytic method, the time-varying effect model (TVEM) [23], to examine whether SM and heterosexual differences in seven well-established sexual orientation related disparities differ across ages 18–65 [2–8]: Outcomes include past-year alcohol, tobacco, and drug use disorders, major depressive episode, generalized anxiety disorder, cardiovascular problems, and STIs.

Consistent with a large and growing body of evidence, we find that SMs experience striking health disparities across a variety of mental, behavioral, and physical health conditions. Our findings, however, demonstrate that the degree to which SMs are more likely to experience poor health varies by age. Findings identify critical periods of vulnerability for the development of these disparities and suggest potential ages to target for prevention and intervention.

Similar to prior research [5–7], we found that SMs have significantly higher odds of AUD and DUD throughout adulthood with slight variation across ages. Yet, our results from TVEM analyses also indicate that the odds of a major depressive episode, anxiety disorder, TUD, STI, and cardiovascular disease among sexual minorities vary by age.

The associations between SM status and depression and anxiety are strongest around age 20 and age 24, respectively. Elevated risk in the early twenties may be related to experience of “coming out” which, for many, occurs in the late teens and early twenties. Furthermore, these youth may still be dealing with the residual effects of school-based victimization, which is more common for SM youth [13] and the effect of which last (at least) into the early 20s [14]. . The decreasing disparity in mental health across adulthood may reflect SMs exiting hostile school and family environments, while simultaneously seeking out supportive networks and communities [14,29,30].SMs have significantly higher odds of TUD in early adulthood (ages 18–28) and the disparity narrows with age. One possible explanation for this narrowing disparity may be that smoking rates among SMs may decline after early adulthood. A key driver of smoking among SMs may be sexual minority stressors, including discrimination [31], which is reported at highest rates in early adulthood [32]. It could also be that the narrowing disparity is not due to decreased tobacco use among SMs as they age, but instead due to elevated rates of tobacco use among older heterosexuals. A recent report from the Centers for Disease Control and Prevention (CDC) indicates that 13% of adults aged 18–24, 18% of adults aged 25–44, and 18% of adults aged 45–64 smoke cigarettes [33]. Notably, this mimics the shape of the trajectories we found for the examined mental health outcomes (GAD and MDE). We hypothesize that these similar trajectories reflect the well-documented relationship between smoking and mental health [34], where persons with mental illness are approximately two times as likely to smoke [23], perhaps as a form of self-medication [35], although smoking may increase the risk of certain mental disorders [36]. We also noted unique patterns for AUD and DUD whereby disparities were largest during 18–20 and then again around the age of 40. Generally, rates of alcohol and drug use peak in early adulthood and decline as people age [21]. It is possible that the sexual-orientation-related disparities in early adulthood are, in part, due to unique milestones for SM adolescents and young adults (e.g., “coming out”), coinciding with normative increases in substance use. Elevated risk for AUD and DUD during midlife, however, is counter to what we might expect and encourage future research attention in to its predictors. This may, for example, be an instance where the explanation may be more related to cohort, rather than a developmental, differences [37].

Finally, cardiovascular disparities were smaller in magnitude and age-specific. The odds of cardiovascular disease were significantly higher for SMs, relative to heterosexuals, from the mid-40s to early 50s. This likely reflects the natural trajectory of cardiovascular disease, where risk of cardiovascular disease increases with age. Thus, the relationship between SM status and cardiovascular health maps on to an age period of heightened risk in the overall population. Given previous findings of significant associations between stress and cardiometabolic risk among SM groups [8], but not among heterosexuals [38], as well as lifelong experiences of sexual-minority-specific discrimination [39], disparities in cardiovascular heath may reflect the effect of chronic stress for SM populations or other health-related behaviors linked to stress (e.g., substance use). Future research should investigate the role of minority stress on the significant cardiovascular health disparity, such that future programs might intervene on that link.

This study had several limitations. First, it is widely recognized that there is heterogeneity in the SM population. Health disparities, for example, have been shown to differ by sexual identity (i.e. gay vs. bisexual) [5, 44] and by biological sex [2,7]. Others have applied an intersectionality framework to examine how SM health disparities differ across racial/ethnic groups [40]. In this analysis, we did not examine the differences within sexual minorities, but instead call attention to developmental differences in sexual orientation health disparities more broadly. Thus, the degree to which disparities vary by age may also significantly differ across subpopulations within the larger SM community is an important focus for future research. Second, we used an inclusive definition of SM status by including those who report any same-sex attraction, behavior, or SM identity [41]. This is a conservative approach, and thus may yield an underestimate of SM health disparities. Future research should explore whether these disparities may be stronger among particular subgroups of SMs. Third, the interpretation of these analyses is limited by our inability to separate age effects from cohort effects. Future longitudinal studies that explicitly collect measures of sexual orientation and related experiences (e.g., discrimination) are needed to better untangle these potentially related and confounding effects. Fourth, our substance abuse measures combine all drug use disorders in to a single item. Although useful in providing the overall prevalence of drug use disorder among SM adults, drug disorders have varying etiologies, prevalence, and contributing factors. Thus, future research examining specific drug abuse prevalence by age is needed to make more directly claims for this population. Finally, the NESARC-III does not include measures of gender identity; we were therefore unable to examine disparities by gender-identity. The absence of gender identity measures in national data have stymied scientific understanding of this population; the measurement of gender identity in future national studies would provide an unprecedented opportunity to address these knowledge gaps.

Future research should continue to explore the etiology of these disparities and, specifically, addressable social factors that contribute to them. The minority stress theory [11, 42], for example, posits that health disparities affecting SMs may be explained by minority specific stress unique to SMs (e.g., internalized stigma, discrimination) [11,43]. It is likely that exposure to SM-related stressors vary as people age, potentially leading to different health outcomes across the life course. Future work should also explore how age-specific disparities vary across other sociodemographic factors known to affect the health of sexual minorities. Furthermore, many of these health factors are co-occurring and interrelated (e.g., smoking and mental health) [34]. Although this analysis focused on addressing each health condition as an independent outcome, future research focused on the developmental timing of risk may aim to understand the co-occurrence of outcomes.

Sexual-orientation-related health disparities persist in most cases across adulthood, but vary in strength by age. These findings inform the timing and targeting of prevention and intervention efforts, suggest focused research efforts on developmental periods where disparities are most salient for SMs, and highlight the need for investigations into developmentally-situated mechanisms that contribute to SM health.