TORONTO - Almost one in five Canadian adults have high blood pressure that puts them at risk for heart attacks, strokes and kidney disease - but a significant proportion are unaware they even have the condition, a survey has found.
The Statistics Canada study, the most comprehensive health survey involving direct physical measures ever carried out in the country, suggests about 4.6 million Canadians aged 20 to 79 have high blood pressure.
"Altogether, we found that the prevalence of hypertension was 19 per cent, and that 19 per cent included both those who were on medication and those whose blood pressure reading was in the hypertensive range," said Kathryn Wilkins, a senior analyst at Statistics Canada who led the study.
"It went up dramatically with age," Wilkins said Wednesday from Ottawa. "In the age group 20 to 39, there was only a prevalence of two per cent of hypertension; at ages 40 to 59, it was 19 per cent; and then at 60 to 79, over half u 53 per cent of people u had hypertension."
A person is considered to have high blood pressure if their top, or systolic, reading is 140 or greater, and the bottom, or diastolic, number is at or exceeds 90. Measurements of 120 to 139 systolic over 80 to 89 diastolic are considered pre-hypertensive.
The 2007-2009 survey of 3,514 adults u a sample that represents 23.7 million Canadians u found that 20 per cent had readings in the pre-hypertension range, while 61 per cent had normal blood pressure.
Wilkins said the Canadian Health Measures Survey is the first to use direct, automated measures of blood pressure and self-reported use of blood pressure medication to build a profile of hypertension among the population.
The study estimates that about 80 per cent of those with hypertension are being treated with drugs, and in two-thirds of cases, the medications are effective in controlling blood pressure.
In about 6.6 per cent, the condition was uncontrolled, meaning that blood pressure remained too high, said Wilkins, noting that prevalence of hypertension was virtually the same in men and women.
However, there were some differences between the sexes.
Among women taking anti-hypertensive medications, 18 per cent had blood pressure that remained out of control, compared with 10 per cent of men on the drugs.
This gap in blood pressure control occurred only at older ages, the survey found. For example, among 60- to 69-year-olds using anti-hypertensive drugs, 19 per cent of women had uncontrolled blood pressure versus seven per cent of men.
So even though men are less likely than women to be aware of their condition, they seem to fare better at shaping up their blood pressure readings, said Wilkins.
"There's a bit of a paradox there," she said. "Women are more likely to be aware of their hypertension, they're more likely to be on medication than men with hypertension. But somehow the success, or the efficacy, of the medication seems to be lower in women than in men."
"And this has been observed in other countries as well, and the reasons really are not understood at this point."