The Effects of Hormone Replacement Therapy on Blood Pressure in Postmenopausal Women

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The summary below is from the full report titled "Hormone Replacement Therapy and Longitudinal Changes in Blood Pressure in Postmenopausal Women." It is in the 21 August 2001 issue of Annals of Internal Medicine (volume 135, pages 229-238). The authors are A Scuteri, AJG Bos, LJ Brant, L Talbot, EG Lakatta, and JL Fleg.

What is the problem and what is known about it so far?

High blood pressure (hypertension) puts people at risk for such complications as heart attacks and strokes. High blood pressure becomes more common as people age; after menopause, it becomes even more common in women than it does in men of the same age. One theory is that the increase in blood pressure in women after menopause is related to the decrease in levels of estrogen and other hormones that occur during that phase of life. It is not known, however, whether treating women with estrogen and progestin (hormone replacement therapy, or HRT) is associated with changes in blood pressure after menopause.

Why did the researchers do this particular study?

To find out whether blood pressure increased less over time in postmenopausal women who took HRT than in women who did not take HRT.

Who was studied?

The researchers studied 226 women who were already participating in a study called the Baltimore Longitudinal Study of Aging. Seventy-seven women took both estrogen and progestin, and 149 used neither hormone. None of the women had high blood pressure at the start of the study.

How was the study done?

At the beginning of the study and then every 2 years, the researchers collected information about the women's blood pressure and factors known to be associated with changes in blood pressure, including exercise, smoking, cholesterol levels, alcohol use, and body size. The study followed women for an average of 5 to 6 years (a minimum of 2 years and a maximum of 18.5 years).

What did the researchers find?

At the start of the study, blood pressure was similar in women who did and those who did not take HRT. Average systolic blood pressure (the first, and higher, number in blood pressure readings) increased less rapidly in women taking HRT than in women who did not take HRT. These differences were found even when the other factors that affect blood pressure were taken into account. Diastolic blood pressure (the second, lower number in blood pressure readings) did not change significantly in either group of women.

What were the limitations of the study?

Women who take hormones tend to be generally healthier and more health conscious than those who choose not to take hormones. It is possible that some of the benefits in blood pressure in the women taking HRT were related to health factors, other than hormone use, that the researchers could not measure.

What are the implications of the study?

Postmenopausal women who take HRT have less of an increase in systolic blood pressure over time than those who do not take HRT.