Lesbian and bisexual women die significantly earlier than heterosexual women, according to a new study, and it’s likely due in part to discrimination.

The role sexuality plays in overall health is a subject that’s attracted researchers for decades, resulting in a large body of evidence of how LGBTQ people experience a variety of negative outcomes, from mental health issues to chronic disease, at elevated rates. But what hadn’t been widely studied is how these outcomes actually affect mortality rates.

The paper, published last month in JAMA, reviewed decades’ worth of data from the Nurses’ Health Study II, which began in 1989 as part of a series of investigations into risk factors for major chronic diseases in women. The authors analyzed how sexuality contributed to premature death rates among the study’s cohort of more than 100,000 U.S. nurses. And what they turned up was an alarming disparity in how long lesbian and bisexual women live in comparison to their heterosexual peers. 

Compared to participants who identified as heterosexual, the analysis found, those who identified as lesbian or bisexual died 26% sooner, with lesbian women dying 20% sooner and bisexual women dying 37% sooner.

“One of the advantages of this study is that we were able to separate out bisexual and lesbian participants, because we had enough people and we followed them for long enough that we can actually look at those risks separately, which no other U.S. study has been able to do,” Sarah McKetta, the JAMA paper’s lead author and a postdoctoral fellow at Harvard Medical School, told NBC News.

Although the team expected to see disparities given the existing research on negative health outcomes, McKetta said they didn’t expect to see such stark differences in mortality rates.  

As McKetta explained, gathering information about premature death rates among LGBTQ communities has proved difficult because questions about sexual orientation weren’t systematically incorporated into U.S. studies prior to 2014. But the Nurses Health Study II was an outlier. In 1995, almost 20 years before it became commonplace, the study’s participants were given the option to self-identify as heterosexual, bisexual, or lesbian, gay or homosexual in a follow-up survey. And it was that data that McKetta and her fellow researchers used, along with records kept by the National Death Index.

“We’ve known for a really long time that there are systemic and highly reproducible health disparities for LGB people, particularly LGB women, across many outcomes,” McKetta said. “We’ve seen disparities in tobacco use and alcohol use, in mental health, in chronic disease. Basically, pretty much any outcome that we’ve looked at across multiple surveys, we see that lesbian, gay and bisexual women are at higher risk. And we also know it’s due to levels of discrimination, ranging from structural to individual. The thing is, we actually don’t really know to what extent these disparities manifest in premature mortality differences, because there’s some real data limitations.”

She added, “This was an opportunity for us to actually quantify the magnitude of that disparity.”

In addition to providing a way for the researchers to compare mortality rates, the Nurses Health Study model allowed them to draw conclusions about how specific health outcomes contributed to differences in mortality rates. Using information gathered on the women 20 years prior — which revealed a twofold prevalence of alcohol and tobacco use, as well as higher risks for breast cancer, cardiovascular disease and depression, among lesbian and bisexual participants — McKetta and her colleagues came to the conclusion that the disparities could be largely attributed to preventable causes. 

“This isn’t something that just happened; this is something that is due to chronic processes and we think is also multifactorial,” McKetta said, pointing to an extra analysis they did involving only the participants who had never smoked, which showed the same disparities in death rates. “It’s not because of one thing; it’s because of a lot of things.” 

At the heart of those factors, McKetta explained, are various layers of discrimination and isolation that lesbian and bisexual women are exposed to on a daily basis. From interactions in health care settings to workplaces and private spaces, these “toxic social exposures,” as she called them, translate into damaging behaviors and negative mental and physical health outcomes. And this is especially true for bisexual women, who experience higher rates of substance abuse and sexual victimization, in addition to having poorer physical health and mental health, than lesbian and heterosexual women.

“If this isn’t research that you typically do, it can be really easy to think that because sexuality is a spectrum, that the risk kind of goes up as people get more exclusively lesbian, more exclusively gay. But actually, the healthcare risks are much more pronounced for bisexual folks,” McKetta said. “They have these dual pressures given their identity, and they experience discrimination from both inside and outside of queer communities.”

McKetta acknowledged that the study portrays a “grim” reality for the participants, who were born between 1945 and 1964. But she’s hopeful that the findings will call attention to the many systems that contribute to poor health outcomes for LGBTQ women and people in general, so that younger generations won’t see the same kind of shortened lifespans as their predecessors. 

“One of the things that I was worried about with this study is that the takeaway would be that it kills to be gay,” she said. “It doesn’t kill to be gay. It kills to be discriminated against. And that’s the lived experience of lesbian and gay women and bisexual women who are just trying to walk through the world.”