Maintaining blood pressure within the optimal range is a key component of heart health and overall physical well-being. Proper blood circulation throughout the body distributes oxygen and other nutrients to the various organs and tissues to sustain bodily functions.
The heart pumps blood by way of blood vessels called arteries. As blood flows through the arteries, it exerts a force against the artery walls that causes what is known as blood pressure.
Blood pressure readings include two measurements resulting from this effect: systolic pressure and diastolic pressure. Systolic pressure refers to the force of the blood during heartbeats. Diastolic pressure is the force that occurs between heartbeats when the heart muscle relaxes.
Elevated levels beyond this range can lead to high blood pressure, also known as hypertension, which increases the risk of cardiovascular diseases such as heart failure and stroke.
However, a new study that appears in Circulation suggests that females may be susceptible to cardiovascular disease at blood pressures lower than the 120 mm Hg threshold.
Dr. Susan Cheng, M.D., MPH, MMSc, director of the Institute for Research on Healthy Aging, led the team of researchers who conducted this study at the Smidt Heart Institute of Cedars-Sinai Medical Center in Los Angeles, CA.
Normal blood pressure for males vs. females
The team analyzed the blood pressure measurements of 27,542 participants, of whom 14,873 (54%) were female.
None of the participants had cardiovascular disease (CVD) at the outset, but 7,424 people, of whom 44% were female, developed nonfatal or fatal CVD over the study period, which spanned 4 decades. There were 3,405 recorded myocardial infarctions, 4,081 cases of heart failure, and 1,901 stroke events.
The researchers focused specifically on the blood pressure measurements among females and how they corresponded to incidents of CVD.
Using a sex-specific model approach, the study analyzed which blood pressure measurements corresponded to incidents of CVD among the female participants.
Previous research has already shown that as blood pressure increases beyond a certain threshold, the occurrence of CVD proportionately increases as well.
However, the data in this study suggest a key difference: For females, this threshold for risk presents itself at a lower blood pressure value.
The study determined a threshold of 120 mm Hg for males, which conforms to the current guidelines. In contrast, for females, the study saw an increased risk for disease at 110 mm Hg, as well as at even lower values.
In addition, the study identified the different ranges of risk for specific heart diseases. For heart failure, females and males shared a similar level of risk at 110–119 mm Hg and 120–129 mm Hg, respectively. For stroke, the risk was comparable at 120–129 mm Hg for females and 140–149 mm Hg for males.
Different threshold risks
While the specific ranges differed across each disease, males consistently displayed a higher threshold for risk than females.
The authors also carried out secondary analyses in which they repeated all models stratified by race, as 66% of the participants were white while only 26% were Black. The researchers also stratified their analysis by age and cohort. For example, they looked at the results after excluding people taking antihypertensive medications.
After doing so, the researchers note that they observed similar trends.
“Our latest findings suggest that this one-size-fits-all approach to considering blood pressure may be detrimental to a woman’s health,” says Dr. Cheng.
A previous study that Dr. Cheng led gives a potential explanation for these inconsistent thresholds and disease susceptibility. The 2020 study found that females display a faster progression of blood pressure elevation than males, with signs showing earlier in life.
The authors suggested a reason for this, pointing to sex differences in the anatomy and physiology of the blood vessels, such as the smaller diameter of arteries in females.
These findings indicate that at the same age and level of high blood pressure, females may be at higher risk of CVD than males.
Next steps in heart health research
Based on the new study, it seems as though the blood pressure level that experts have considered normal may not be the precise optimal range for females. This potential misunderstanding, which highlights a gap in the existing body of research, raises critical issues regarding the prevention and treatment of heart disease. Dr. Cheng says:
“Based on our research results, we recommend that the medical community reassess blood pressure guidelines that do not account for sex differences.”
Additional research is necessary to determine the threshold at which it is important to treat females for hypertension — whether this remains at 120 mm Hg or lowers to a level closer to 110 mm Hg.
The team plans to carry this research forward with the intention of expanding on the scientific knowledge of female cardiovascular health.