Weathered by a lifetime of racial discrimination, Black women age earlier and faster. Researchers theorize this accelerated health deterioration is caused by cumulative exposure to race-based stressors in a race-conscious society. \nHigh levels of stress hormones can be toxic for Black women’s bodies, especially if the women are repeatedly pushed into a fight-or-flight state by prejudice, marginalization, institutional bias, and oppression. The ‘weathering’ hypothesis dates back to 1992 when Arline T. Geronimus, ScD, proposed it after learning that young Black women had better pregnancy outcomes in their late teens than in their mid-twenties. By contrast, she found White women faced the lowest risk of pregnancy complications in their mid-twenties and the highest risk in their teens. \n“There was certainly a whole narrative that teen motherhood somehow caused perpetual poverty, lack of education, and poor birth outcomes,” Geronimus said in a 2018 interview with NPR. “[But] the data spoke for themselves — that the risks were higher in black young women the later they waited to have children, and that was not true for white [women].”\nDue to this premature aging, Black women’s experiences have effectively been erased from many research narratives. In 1994, the Study of Women’s Health Across the Nation (SWAN) began analyzing the health of middle-age and older women over time, through participation of women who were likely to undergo menopause. But, in line with the hypothesis that Black women age earlier due to weathering, many were excluded from SWAN after experiencing menopause earlier. \nIn November, Alexis Reeves, PhD, authored a new study that enrolled the approximately 9,000 women who had been excluded under the guidelines of the previous SWAN study. This ‘enrollment’ involved matching up the women’s profiles to similar participants who had been included, in order to compare their health outcomes. She sought to break down how selection bias and racial disparities in these cohort studies painted falsely high estimates for age of onset of chronic diseases by not taking women of color into account.\nAcross the board, inclusion of these women in the study lowered the average age of developing many critical diseases. Compared to the estimates originally concluded by the SWAN study, Reeves found that heart diseases begin 5 years earlier in Black and Hispanic women, while insulin resistance begins 11 years earlier. The results show that interventions for hypertension and metabolic diseases in Black and Hispanic women should target these groups much earlier than originally estimated based on SWAN’s data.\nThis is further troubling because studies usually determine the age range for recruitment of participants based on the average age of onset — women of color would have been more likely to develop the health outcome by the recruitment age, and therefore be excluded from study.\n“I wasn’t expecting to see how much the selection [of study participants] changed these estimates,” Reeves told Science. “We’re overestimating the timing of onset of these diseases for everyone in SWAN, regardless of race. It basically amounts to only telling part of the story.”\nGeronimus equated the idea of weathering to the tabletop game, Jenga. As more pieces are pulled from the tower, the structure can no longer stand and collapses. \nAllostatic load — the physiological burden of constant adaptation to stressors — is one way of measuring weathering. Higher allostatic load scores are connected to older age, heightened mortality, brain health decline, and low socioeconomic status. Measuring this load involves tracking biomarkers such as levels of cortisol and of epinephrine, alongside the outcomes of this stress on blood-pressure reactivity and cholesterol levels. \nIn addition to high allostatic load, weathering has been tied to telomere shortening. Telomeres — the structure at the ends of a chromosome — help protect chromosomal stability, and shorten with age. Critically short telomeres prevent a cell from dividing, which triggers a cell to either die or enter an inactive state. Shorter telomeres are overall a risk factor for development of cancers, cardiovascular diseases, diabetes, and other diseases. While telomeres naturally shorten after each round of cell division, chronic stress has been tied to higher telomere shortening rates. Weathering may also be measured in epigenetics, which refers to stable changes in the DNA sequence caused by environmental and behavioral factors. This DNA methylation can either prevent or promote the expression of particular genes in one’s DNA, countering the popular notion that health disparities between populations are related to inherent DNA differences. The reality is that epigenetics can rewrite this ‘destiny’ in response to influences such as chronic stress.\nGeronimus found that by age 45, half of Black women had high allostatic load scores, while by age 64, more than 80% did. Socioeconomic status could not explain the racial disparities — poor and nonpoor Black women faced the highest probabilities of having high allostatic load scores.\nIf the goal of clinical research studies is to gather data on women’s health and inform the implementation of interventions against disease, we must address the exclusion of women of color. Knowing the reality of weathering, recruitment ages for studies like SWAN need to adjust. Racially-based stressors result in real disparities in morbidity and mortality rates, illustrating women are not one homogenous population.