Sex differences in 'normal' blood pressure and associated CVD risk

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Women have a lower "normal" blood pressure range compared to men and that this is linked to risk for each specific cardiovascular disease (CVD) type, including heart attack, heart failure, and stroke, found a large study from the Smidt Heart Institute at Cedars-Sinai Medical Centre shows.

Currently, established blood pressure guidelines state that women and men have the same normal healthy range of blood pressure. But this research shows there are differences in normal blood pressure between the sexes.

"Our latest findings suggest that this one-size-fits-all approach to considering blood pressure may be detrimental to a woman's health," said Dr Susan Cheng, associate professor of cardiology and director of the Institute for Research on Healthy Aging in the department of cardiology at the Smidt Heart Institute and senior author of the study. "Based on our research results, we recommend that the medical community reassess blood pressure guidelines that do not account for sex differences."

For years, 120 mmHg has been considered the normal upper limit for systolic blood pressure in adults. Persistent elevations above this limit amount to hypertension-which is well known as the key risk factor for common cardiovascular diseases, such as heart attack, heart failure, and stroke.

In their newest study, Cheng and her research team examined blood pressure measurements conducted across four community-based cohort studies, comprising more than 27,000 participants, 54% of whom were women.

In doing so, the research team identified that while 120 mmHg was the threshold of risk in men, 110 mmHg or lower was the threshold of risk in women. Systolic blood pressure levels that were higher than these thresholds were associated with risk for developing any type of cardiovascular disease, including heart attack, heart failure and strokes.

Investigators also found that women had a lower blood pressure threshold than men for risk of each specific cardiovascular disease type, including heart attack, heart failure, and stroke.

"We are now pushed to rethink what we thought was a normal blood pressure that might keep a woman or a man safe from developing heart disease or stroke," added Cheng, who also serves as director of cardiovascular population sciences at the Barbra Streisand Women's Heart Centre and is the Erika J Glazer chair in women's cardiovascular health and population science.

These findings build on past research led by Cheng suggesting women's blood vessels age faster than men's. Cheng's research, published last year, confirmed that women have different biology and physiology than men and also explained why women may be more susceptible of developing certain types of cardiovascular disease and at different points in life.

With both the 2020 study and in their latest work, Cheng and her team compared women to women and men to men, rather than the common model of comparing women to men.

"If the ideal physiologic range of blood pressure truly is lower for females than males, current approaches to using sex-agnostic targets for lowering elevated blood pressure need to be reassessed," said Dr Christine Albert, chair of the department of cardiology at the Smidt Heart Institute. "This important work is far-reaching and has numerous clinical implications."

As a next step, researchers plan to study whether women should be treated for hypertension when their systolic blood pressure is higher than 110, but still lower than the systolic measurement of 120 for men.

 

Study details
Sex Differences in Blood Pressure Associations With Cardiovascular Outcomes

Hongwei Ji, Teemu J Niiranen, Florian Rader, Mir Henglin, Andy Kim, Joseph E Ebinger, Brian Claggett, C Noel Bairey Merz, Susan Cheng

Published in Circulation on 15 February 2021

Abstract
For decades, 120 mm Hg has been considered the normal upper limit for adult systolic blood pressure (SBP). Practice guidelines have long referred to this threshold for classifying ranges of blood pressure (BP) elevation and treatment targets, given the consistent epidemiologic finding that cardiovascular disease (CVD) risk is continuously increased from the SBP level of 120 mm Hg and upwards. Amid previous studies using outcomes associations to determine a normal SBP range, there remain limited data on potential sex differences. It is well known that BP levels in adulthood are on average lower in women than men in the healthy state; however, whether or not a lower range of SBP might be considered normal for women versus men is unclear.
We studied 27 542 participants (54% women) without baseline CVD who had standardized SBP measurements performed in 1 of 4 community-based cohort studies: the Framingham Heart Study, Multi-Ethnic Study of Atherosclerosis, Atherosclerosis Risk in Communities Study, and Coronary Artery Risk Development in Young Adults Study. Age and race distributions were similar between sexes (standard mean difference <0.1). Over 28±12 years, 7424 participants (44% women) developed nonfatal or fatal CVD: 3405 myocardial infarction (MI), 4081 heart failure (HF), and 1901 stroke events. We related SBP category (defined by 10 mm Hg increments from <100 mm Hg to ≥160 mm Hg) with incident CVD using cohort-stratified Cox proportional hazards models accounting for competing risks and adjusting for traditional risk factors; we observed no important violations of the proportional hazards assumptions. We tested for sex interactions and analyzed the MI, HF, and stroke outcomes separately. We also constructed models stratified by age, race, and cohort. We used R version 3.5.1 to perform analyses, with a 2-sided P<0.05 considered statistically significant. All participants provided written informed consent, institutional review boards approved all protocols, and National Heart, Lung, and Blood Institute approved data access. All data are available through public access policies of the National Heart, Lung, and Blood Institute (BioLINCC ) repository, which does not contain information that could compromise research participant privacy.

 

Cedars Sinai Medical Centre material

 

Circulation study (Open access)

 

 

See also MedicalBrief archives:

Large variability in blood pressure readings between anatomical sites

 

Above normal BP in midlife linked to increased brain damage in later life

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