SAN FRANCISCO, CA — The factors that drive blood pressure in middle age differ in men and women, suggesting that gender-specific treatments for hypertension may be of benefit, a new study shows[1].

An increase in any one of the three factors that determine blood pressure—heart rate, stroke volume, and total peripheral resistance—can lead to an increase in blood pressure.

"The key takeaway from this study is that, for young and middle-aged women, stroke volume was the main determinant of blood pressure, while, in men, vascular resistance was the main determinant of blood pressure," study author Dr Catriona Syme (Hospital for Sick Children, Toronto, ON) said in a statement.

The study was presented at the 2017 American Heart Association (AHA) Council on Hypertension, AHA Council on Kidney in Cardiovascular Disease, American Society of Hypertension Joint Scientific Sessions.

Syme and colleagues studied 1347 Canadians from the Saguenay Youth Study, including 911 adolescents 12 to 18 years old (52% female) and 426 young to middle-aged adults 36 to 65 years old (56% female).

Beat-by-beat systolic BP (SBP) and diastolic BP (DBP), together with heart rate, stroke volume, and total peripheral resistance were measured with a Finometer (Finapres Medical Systems) throughout a 52-minute protocol designed to mimic daily-life activities, such as changes in posture and mental stress.

The relative contributions of stroke volume, total peripheral resistance, and heart rate to SBP and DBP showed "marked sex differences," the researchers report in their conference abstract.

In females, stroke volume explained 55% of the variance in SBP vs only 35% in males. In males, the major determinant of SBP was total peripheral resistance, which explained 47% of the variance, vs only 30% in females. These gender differences were seen across most of the 52-minute protocol, being most prominent during standing and least evident during mental stress, the researchers say.

These results "underscore the need for sex-specific treatments for hypertension (not recommended currently), which affects 3% to 5% of adolescents and 23% to 58% of young to middle-aged adults," they conclude.

A limitation of the study is that it was conducted in white subjects. "Future studies should investigate whether the relative contributions of these parameters differ by race," the researchers note.

Volume vs Resistance

Commenting on the study for theheart.org | Medscape Cardiology, AHA spokesperson Dr Willie Lawrence Jr (Midwest Heart & Vascular Specialists, Kansas City, MO), said these results suggest that "more often in women than in men, it's the volume of blood in each contraction that is contributing to hypertension, whereas in men it's the resistance in the blood-pressure bed that is contributing more to hypertension.

"Therefore, theoretically, if you could decrease the stroke volume per beat in women, which may be done by a diuretic, that would be a more effective way in most women of treating hypertension as a first-choice drug. In men, it may be more beneficial to use a drug that lowers resistance and that may be an ACE inhibitor or a calcium-channel blocker rather than a diuretic," Lawrence said.

However, this may also be influenced by the population in this study, he noted. "This was a population of mainly whites, so the degree to which you can broadly apply the findings is diminished," Lawrence said.

The study was funded by the Canadian Institutes of Health Research, Canadian Foundation for Innovation, and the Heart and Stroke  Foundation of Canada. The authors have no relevant financial relationships.

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