Study Identifies Significant Link Between Hypertensive Disorders of Pregnancy and Stroke in Black Women

Shanshan Sheehy, MD, MSc, ScD

Findings from the Black Women’s Health study (BWHS), a prospective cohort of US Black women who enrolled in 1995, showed that a history of hypertensive disorders of pregnancy (HDOP) was associated with an estimated 66% increased long-term risk of stroke. Investigators concluded that this association may contribute to the disproportionately higher stroke incidence in Black women given the higher prevalence of HDOP in this population.

Over a median of 22 years of follow-up, the study identified 1555 incident strokes, including 310 among 4938 women with a history of HDOP. Led by Shanshan Sheehy, MD, MSc, ScD, assistant professor of medicine, Boston University School of Medicine, the age-adjusted hazard ratio (HR) for HDOP vs no HDOP was 1.72 (95% CI, 1.52-1.95). After additional control for age at first birth, body mass index (BMI) at age 18 years, educational attainment, and parental history of stroke, the HR was 1.66 (95% CI, 1.46-1.89).

"Our study provides evidence that pregnancy history may be an important factor for risk assessment and prevention of long-term stroke,” Sheehy said in a statement.¹ "Cardiovascular screening recommendations for Black women in particular should take the history of HODP into account."

Stroke cases were ascertained through biennial BWHS questionnaires, which asked participants to self-report occurrences of physician-diagnosed stroke. The primary analyses included all self-reported first-onset strokes except those that were disconfirmed by neurologist adjudication, as well as fatal strokes identified through NDI, for a total of 1555 incident cases in 42,924 women. A secondary analysis using only confirmed cases (n = 576) was also conducted.

On multivariable analysis, the HRs for HDOP vs no HDOP were 1.53 (95% CI, 1.29-1.82) for preeclampsia and 1.81 (95% CI, 1.53-2.13) for gestational hypertension without preeclampsia. Even after the exclusion of 12 strokes (<.01%) within the first year of pregnancy, the results remained unchanged. In studies based primarily on White women, preeclampsia has been estimated to be associated with 1.5 to 2 times the risk of all cardiovascular disease and of stroke specifically.

"The slightly stronger association for gestational hypertension than for preeclampsia in our study is consistent with findings from prior studies in White women," the study authors wrote.² "We speculate that HDOP subtypes may be more complicated than representing simply a spectrum of severity and may represent different disease phenotypes."

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In the secondary analysis restricted to confirmed strokes, the multivariable HR for any HDOP relative to none was 1.73 (95% CI, 1.41-2.13), with comparable HRs for preeclampsia (HR, 1.63; 95% CI, 1.23-2.16) and gestational hypertension (HR, 1.85; 95% CI, 1.41-.2.43). Among participants who had only 1 birth (strokes; n = 393), the HR for stroke risk for any HDOP vs no HDOP was 1.80 (95% CI, 1.39-2.34). Similarly, the HRs for preeclampsia and gestational hypertension were 1.83 (95% CI, 1.29-2.58) and 1.77 (95% CI, 1.24-2.53), respectively.

While the study is strengthened by the large sample size and number of incident strokes, there were several limitations, including the lack of medical records for all participants who reported stroke. Sheehy et al noted that it is possible that some women who reported gestational hypertension may actually have undiagnosed chronic hypertension, and that such misclassification may have led to inflated estimates of the relative risk. Given the young age at first pregnancy in this cohort, the number of women affected may be minimal.

In age-stratified analyses, HRs for HDOP and stroke risk were 1.88 (95% CI, 1.55-2.26) among women under 55 years of age and 1.52 (95% CI, 1.28-1.80) among women 55 years and older. These associations were consistent across strata of BMI and residence in the Stroke Belt, a region of higher stroke mortality in the Southeastern US. At the conclusion of the study, investigators estimated that 7% (95% CI, 5-9) of stroke cases in the overall population were attributable HDOP. Population attributable fractions were 6% (95% CI, 3-9) for preeclampsia and 9% (95% CI, 6-12) for gestational hypertension.

REFERENCES
1. New study: Black women with hypertensive disorders of pregnancy have increased risk of stroke. News release. Boston University School of Medicine. July 6, 2023. Accessed August 16, 2023. https://www.eurekalert.org/news-releases/994761
2. Sheehy S, Aparicio HJ, Xu N, et al. Hypertensive disorders of pregnancy and risk of stroke in US Black women. NEJM Evid. Published online July 6, 2023. doi:10.1056/EVIDoa2300058