By Shannon Firth 

Across a large population of female nurses, those identifying as lesbian or bisexual had earlier mortality compared with their heterosexual counterparts, a prospective cohort study showed.

Among 90,833 women in the Nurses' Health Study II, lesbian and bisexual participants had earlier mortality compared with heterosexual women (adjusted acceleration factor 0.74, 95% CI 0.64-0.84), reported Sarah McKetta, MD, PhD, of Harvard Pilgrim Health Care Institute in Boston, and co-authors.

These differences were greatest among bisexual participants (adjusted acceleration factor 0.63, 95% CI 0.51-0.78) followed by lesbian participants (adjusted acceleration factor 0.80, 95% CI 0.68-0.95), they wrote.

There were 4,227 deaths reported, with cumulative mortality rates of 4.6% among heterosexual women, 7% among gay women, and 10.1% among bisexual women.

"Looking at the subgroup differences, we were really floored by how pronounced they were," said McKetta.

Cancer, respiratory diseases, suicide, and heart disease represented the leading causes of death among the sample.

Extensive research has documented greater health risks for lesbian and bisexual women, including psychiatric morbidity and substance use, cardiovascular disease, and many cancers, relative to their heterosexual peers, McKetta said. "And we also know that many of these risks are even more pronounced among bisexual women," she added.

Notably, when "compared with lesbian participants, there was more divergence for bisexual participants from heterosexual participants, but it did not reach statistical significance," the authors wrote.

One possible explanation for the findings is that bisexual women experience more pressure to conceal their sexual orientation, McKetta said, noting that most bisexual women have male partners. "Concealment used to be thought of as sort of a protective mechanism ... but [it] can really rot away at people's psyches and that can lead to these internalizing problems that are also, of course, associated with adverse mental health," she said.

While McKetta and her colleagues didn't specifically study concealment as a mechanism, "we think based on prior literature, this is one of the driving forces," she said.

While McKetta and team chose not to control for most health-related factors, such as alcohol use and diet, since "these are likely on the mediating pathway between LGB [lesbian, gay, and bisexual] orientation and mortality," they did conduct a sensitivity analysis on smoking, as it is the "leading cause of premature mortality."

However, among the 59,220 women who reported never smoking, lesbian and bisexual women still had earlier mortality than heterosexual women (acceleration factor for all lesbian and bisexual women 0.77, 95% CI 0.62-0.96).

"And so even though, obviously, smoking is a critical contributor to the mortality risk, it's not explaining all of the risks," McKetta said. This means the risk for mortality is likely due to multifactorial causes, and not one pathway, disease process, or behavior, she explained.

The study authors also conducted a secondary analysis looking at race and ethnicity and found even higher disparities in mortality among racial and ethnic minority lesbian and bisexual women compared with their white counterparts; however, those results were not statistically significant due to their small numbers.

For this study, McKetta and colleagues used data from the Nurses' Health Study II on women born between 1945 and 1964 and initially recruited in the U.S. in 1989. They were followed until April 2022. A 1995 survey was used to assess the primary outcome of time to all-cause mortality.

Mortality was based on reports to study personnel of participants' deaths from a close contact and confirmed in the National Death Index (NDI). If a participant had not responded to several study questionnaires, study personnel looked for a death record in the NDI.

Of the 116,149 eligible study participants, 78% had valid sexual orientation data. Of those, 98.9% identified as heterosexual, 0.8% identified as lesbian, and 0.4% identified as bisexual.

Of this group, the majority were white, and a greater share of heterosexual participants reported never smoking compared with lesbian and bisexual participants (65.4% vs 46.1%).

"These findings may underestimate the true disparity in the general U.S. population," the authors wrote, adding that the study population "is a sample of racially homogeneous female nurses with high health literacy and socioeconomic status, predisposing them to longer and healthier lives than the general public."

"We think that that means that our estimate is, unfortunately, conservative," McKetta noted.

In the future, she said she hopes to explore causes of death in this population, for which data were incomplete at the time of the study.

Across a large population of female nurses, those identifying as lesbian or bisexual had earlier mortality compared with their heterosexual counterparts, a prospective cohort study showed.

Among 90,833 women in the Nurses' Health Study II, lesbian and bisexual participants had earlier mortality compared with heterosexual women (adjusted acceleration factor 0.74, 95% CI 0.64-0.84), reported Sarah McKetta, MD, PhD, of Harvard Pilgrim Health Care Institute in Boston, and co-authors.

These differences were greatest among bisexual participants (adjusted acceleration factor 0.63, 95% CI 0.51-0.78) followed by lesbian participants (adjusted acceleration factor 0.80, 95% CI 0.68-0.95), they wrote.

There were 4,227 deaths reported, with cumulative mortality rates of 4.6% among heterosexual women, 7% among gay women, and 10.1% among bisexual women.

"Looking at the subgroup differences, we were really floored by how pronounced they were," said McKetta.

Cancer, respiratory diseases, suicide, and heart disease represented the leading causes of death among the sample.

Extensive research has documented greater health risks for lesbian and bisexual women, including psychiatric morbidity and substance use, cardiovascular disease, and many cancers, relative to their heterosexual peers, McKetta said. "And we also know that many of these risks are even more pronounced among bisexual women," she added.

Notably, when "compared with lesbian participants, there was more divergence for bisexual participants from heterosexual participants, but it did not reach statistical significance," the authors wrote.

One possible explanation for the findings is that bisexual women experience more pressure to conceal their sexual orientation, McKetta said, noting that most bisexual women have male partners. "Concealment used to be thought of as sort of a protective mechanism ... but [it] can really rot away at people's psyches and that can lead to these internalizing problems that are also, of course, associated with adverse mental health," she said.

While McKetta and her colleagues didn't specifically study concealment as a mechanism, "we think based on prior literature, this is one of the driving forces," she said.

While McKetta and team chose not to control for most health-related factors, such as alcohol use and diet, since "these are likely on the mediating pathway between LGB [lesbian, gay, and bisexual] orientation and mortality," they did conduct a sensitivity analysis on smoking, as it is the "leading cause of premature mortality."

However, among the 59,220 women who reported never smoking, lesbian and bisexual women still had earlier mortality than heterosexual women (acceleration factor for all lesbian and bisexual women 0.77, 95% CI 0.62-0.96).

"And so even though, obviously, smoking is a critical contributor to the mortality risk, it's not explaining all of the risks," McKetta said. This means the risk for mortality is likely due to multifactorial causes, and not one pathway, disease process, or behavior, she explained.

The study authors also conducted a secondary analysis looking at race and ethnicity and found even higher disparities in mortality among racial and ethnic minority lesbian and bisexual women compared with their white counterparts; however, those results were not statistically significant due to their small numbers.

For this study, McKetta and colleagues used data from the Nurses' Health Study II on women born between 1945 and 1964 and initially recruited in the U.S. in 1989. They were followed until April 2022. A 1995 survey was used to assess the primary outcome of time to all-cause mortality.

Mortality was based on reports to study personnel of participants' deaths from a close contact and confirmed in the National Death Index (NDI). If a participant had not responded to several study questionnaires, study personnel looked for a death record in the NDI.

Of the 116,149 eligible study participants, 78% had valid sexual orientation data. Of those, 98.9% identified as heterosexual, 0.8% identified as lesbian, and 0.4% identified as bisexual.

Of this group, the majority were white, and a greater share of heterosexual participants reported never smoking compared with lesbian and bisexual participants (65.4% vs 46.1%).

"These findings may underestimate the true disparity in the general U.S. population," the authors wrote, adding that the study population "is a sample of racially homogeneous female nurses with high health literacy and socioeconomic status, predisposing them to longer and healthier lives than the general public."

"We think that that means that our estimate is, unfortunately, conservative," McKetta noted.

In the future, she said she hopes to explore causes of death in this population, for which data were incomplete at the time of the study.