The percentage of older women whose high blood pressure was not in control, despite being on medication, was almost double that of older men, the study revealed — to the surprise of the researchers involved.
Dr. Norm Campbell, one of the authors, said the finding is "a head-scratcher."
"Why would it be women as compared to men? I was shocked when I saw that data. I would have predicted that men would have been more uncontrolled than women," said Campbell, an internal medicine specialist and professor of medicine at the University of Calgary.
Campbell said the researchers tried to see if differences in things like body mass index, underlying health status, socio-economic standing and type of blood pressure medication the people were on could explain away the difference they saw between women and men.
But none of those factors seemed to be responsible. "We don't have a good explanation," Campbell said.
The reason the authors found the gap startling is that women are generally better at taking care of their health than men.
But these findings suggest that there may be some biological difference at play with blood pressure control. Campbell said it may mean that older women with hypertension — what the medical community calls high blood pressure — need to be treated more aggressively.
The findings were drawn from the 2009-2010 cycle of the Canadian Health Measures Survey. Data for that survey was collected from March 2007 through February 2009.
Participants were selected to create a representative sample of Canadians. They were asked to filled in questionnaires and undergo physical examinations.
This particular analysis looked at hypertension in respondents aged 60 to 79. The findings were published Wednesday in the October issue of Statistics Canada's journal Health Reports.
They showed that in this age group, an equal proportion of women and men had high blood pressure, roughly 60 per cent. And most of them were taking blood pressure medications — 84 per cent of the men and 89 per cent of the women. (The difference between those two figures isn't statistically significant.)
Despite the fact that a virtually equal percentage took the prescribed medications, about 30 per cent of women didn't have their hypertension under control, compared to 17 per cent of men.
Hypertension was defined as a systolic blood pressure of 140 or above and a diastolic blood pressure of 90 or above.
High blood pressure increases an individual's risk of experiencing a stroke or developing heart disease. The primary causes of high blood pressure are lifestyle related — eating too much salt, getting too little exercise, becoming overweight, drinking too much alcohol.
Addressing the root cause is preferable, but often not achievable. As a result, many people with high blood pressure are treated with drugs, generally some combination of diuretics, ACE-inhibitors, beta blockers, calcium channel blockers and angiotensin receptor blockers.
Campbell said family doctors and older women with high blood pressure should be aware of this discrepancy in treatment success, and move quickly when blood pressure control appears to be slipping.