An inclusive review of decades’ worth of data reveals new insight into menopause and aging in women of color, suggesting Black and Hispanic women are likely to experience menopause measurably earlier than those who are white. The researchers say the difference is possibly caused by the grinding daily stresses of racism.
The study, published on Thursday in the International Journal of Epidemiology, pulls data from one of the largest, longest-running efforts to understand the health of women as they age and experience menopause. Launched in 1994, the ongoing project, known as the Study of Women’s Health Across the Nation (SWAN), spans seven research centers and has recruited more than 3,000 participants across five racial and ethnic groups and a diverse range of socioeconomic backgrounds and cultures.
But despite their deliberate and extensive efforts to provide inclusive data, the SWAN scientists recently noticed that some women had still been left out: many postmenopausal people who volunteered for the study—particularly those who were Black and Hispanic—had inadvertently been excluded.
Alexis Reeves, a SWAN investigator and then a Ph.D. student at the University of Michigan, wanted to address the representation gap through her doctoral research. “My first thought was ‘How do we understand that bias?’” says Reeves, who is first author of the new study. She and her then adviser Siobán Harlow, an epidemiologist and SWAN investigator, who co-authored the new paper, found a statistical workaround to the project’s exclusion problem, essentially adding those excluded participants back into SWAN.
One reason for the earlier onset of menopause among Black women is that they experience surgical menopause, which results from the removal of the ovaries and sometimes the uterus, roughly twice as often as white women, according to data from SWAN. This is in part because Black women have a higher prevalence of benign tumors known as uterine fibroids, says gynecologic oncologist Kemi Doll of the University of Washington, who was not involved with the new research. The study highlights the importance of considering women’s health beyond reproduction and pregnancy and the intricate ways that racism in broader society can bias the scientific process and results, Doll says. “We need more research like this that understands how complex the variable of race is,” she adds. “Race is not just another variable like height or age. It has powerful influences on almost every aspect of what you’re studying.”
It’s unsurprising that Black women experience menopause at a different time than white women, Doll says, because other aspects of their reproductive health—such as their age during their first menstrual period, maternal mortality and rates of reproductive cancers—are markedly different, too. If the data are validated by other studies, the new paper could prompt discussion about when people should be screened for conditions such as endometrial cancer, which is more likely to occur after natural menopause. Doll adds, however, that it’s common among the Black women she treats to have family history with either surgical menopause that occurs very early in life or natural menopause that occurs much later than average. “I could have seen it going either way in terms of [menopause beginning] younger or older,” she says.
Reeves, who is now a postdoctoral researcher in epidemiology at Stanford University, spoke to Scientific American about what the new SWAN study means for understanding racial disparities in women’s health.
[An edited transcript of the interview follows.]
The SWAN investigators tried hard to be inclusive, but people were still excluded. How did that happen?
When SWAN was being put together, the investigators noted that the median age of menopause was 51, so they included menstruating women from ages 42 to 52 in the study. They wanted to track people’s experience of menopause, so they decided people who had already been through it would be ineligible. They screened about 14,000 women who wanted to participate in the study. I looked at those data and found that Black and Hispanic women were most likely to be deemed ineligible, compared with all other racial and ethnic groups. Our results [in the new study] really underline how the eligibility criteria set out by researchers could be a huge barrier for a lot of populations to be included in research.
What made these volunteers ineligible for the study?
[It was] using a median age of menopause based on mostly white populations, especially if there are women who are kind of systematically going through menopause much earlier than that average age. Black women had twice the likelihood of being excluded from the study for this reason. Thirty percent of Black women who were not included had already had surgical menopause.
If a 52-year-old person who wanted to be part of the study was a Black or Hispanic woman, she would be less likely to be included than a white, Japanese American or Chinese American woman [of the same age] because she would be more likely to have gone through menopause already.
Why did you think there would be a link between a person’s race or ethnicity and age at menopause?
I came into SWAN really interested in weathering, which is this idea that accelerated aging or early morbidity and mortality happen in particularly marginalized groups such as minority racial groups because of the wear and tear of constant exposure to discrimination.
The main biological pathway involved that has been well studied is stress. Experiencing stress activates your fight-or-flight response, and that constant activation throughout your life leads to higher inflammation. You can measure it through a combination of markers of inflammation and stress such as cortisol, lipid levels and hypertension. Those are put together into a score where a higher number is linked to an increased risk of cardiovascular disease and mortality.
In minoritized populations, you can see that score go up in a person’s early 30s or 40s, compared with white people, where you might not see the score go up until say age 50 or 60. Hypertension is a perfect example—you see it much earlier in Black people than the typical white person in the U.S.
I haven’t seen a lot of work on the association between stress and the timing of menopause yet. There’s more work to be done, especially in this context of racial disparities, to understand how weathering could be connected to natural menopause.
How did your new study include the excluded postmenopausal women?
The statistical analysis we did sort of emphasizes the people who were included in the SWAN study who were representative of the people who were screened for the study but didn’t make it in. So we tried to make the SWAN sample more representative by this weighting scheme essentially. This is not perfect. It would be much better to include these women earlier, but it was a way to try to mitigate this bias as best as we could using the data that we had. [Editor’s Note: SWAN screened about 14,000 participants, of whom about 3,000 were included in the study. In the new paper, the authors identified people in the screened group who were ineligible because they were postmenopausal. For instance, a 52-year-old Black woman who experienced menopause at age 49 may have been included if she had enrolled a few years sooner. The new study’s authors reanalyzed the updated SWAN data that accounted for these missing participants.]
What did you find?
Prior to our analysis, there were no racial differences in the timing of menopause found in SWAN’s previous analyses. Once we accounted for this selection process, there was about a 1.2-year difference between Black and white women. Black women in the study have natural menopause about 0.6 year earlier and surgical menopause almost two years earlier on average. In studies of the timing of menopause, surgical menopause is often kind of forgotten about and left out of the analysis. Black women have the highest rates of surgical menopause. [They had] double the rates of surgical menopause coming into the study and had higher rates in the study as well.
Surgical menopause rates for Hispanic women were similar to those of white women in SWAN and in our analysis. Even though Hispanic women have similar rates of surgical menopause, compared with white women, both Black and Hispanic women in SWAN had surgical menopause at significantly earlier ages than white women. Black women had it even earlier than Hispanic women, but in both groups the average age was still significantly earlier than that of white women. The data confirms other studies that have shown similar rates of hysterectomy for Hispanic versus white women, but I believe that this is one of the first studies to show that Black and Hispanic women experience surgical menopause at earlier ages than white women. Japanese American and Chinese American women have natural menopause on average later than white women. And they have very low rates of surgical menopause—the lowest rates in our study.
How did you infer that the differences in menopause were because of experiencing discrimination and not for other reasons?
Even when we accounted for things like socioeconomic status and differences in health behaviors, such as alcohol use and exercise, there were still these racial differences in menopause. That kind of points to something that was unmeasured—something about being in this social construct, of being categorized as Black or Hispanic in the U.S., that is contributing to this difference. The next step is probably to study the stress factors that we know are really associated with weathering to see if those can explain some of these racial differences.
Why does the timing of menopause matter to people’s health?
We know that the menopausal period is an important programming time for the body. Your risk of cardiovascular disease, Alzheimer’s disease and dementia—and early mortality—can really be altered or modified during that menopausal transition. There are lots of chronic diseases that can happen earlier in life if you go through menopause earlier, whether it’s surgical or natural. So where and when it happens and how long it lasts can be very important. As our population is aging and living much longer, this transition is an even more important window to a person’s health in the 20 or 30 years after menopause.
We also know that Black women have a shorter life span on average than white women in the U.S. Black women have a higher risk of cardiovascular disease and diabetes as they age as well. I think we can look to menopause as a potential inflection point—a time that could be contributing to those racial disparities and maybe a time for intervention as well.