The average blood pressure of New Zealanders in middle life appears to have increased, an "alarming" finding that could contribute to a predicted rise in the heart attack death rate after a 40-year-long reduction.
Hypertension - abnormally high blood pressure - increases the risk of stroke, heart failure and heart-artery disease. It can also eventually damage the kidneys and eyes. High blood pressure can be caused by obesity, high intake of salt or alcohol, and lack of physical activity.
Otago University researchers have published results of the first national check of blood pressure, based on tests of 4407 people done as part of the 2008/9 adult nutrition survey.
Comparisons were made with Auckland blood pressure studies dating from 1982. Published in the latest New Zealand Medical Journal, the new study found that 31 per cent of adults had hypertension, yet only 15 per cent of the whole sample were using medication to treat the condition.
Compared with a 2002 Auckland study, average pressure when the heart was pumping (systolic) and not pumping (diastolic) had increased in most age/sex categories. One of the most marked increases was in the average systolic blood pressure for men aged 45 to 54, to 133.8mm of mercury, from 123.9mm.
The study authors, including Dr Rachael McLean and Professor Jim Mann, say in their journal paper that mean systolic blood pressure has increased since 2002 in the NZ European and other (NZEO) ethnic category for those aged 35-54 and Maori aged 35-74, reversing a downward trend observed in NZEO between 1982 and 2002.
"It really is quite alarming," Professor Mann told the Herald.
Dr McLean said the 2008/9 check was "just one data-point" suggesting blood pressure had risen and repeat checks - which the Health Ministry had indicated it was planning - were needed to confirm a trend.
"When you put it in the context of the increase in other important risk factors like the increase in the prevalence of diabetes and impaired glucose tolerance and increased prevalence of obesity ... it is quite alarming."
The research paper cites 2006 projections by Heart Foundation medical director Professor Norman Sharpe and others which suggested the heart attack death rate, despite its downwards trend since the late 1960s, may increase for men born after 1956 and women born after 1961.
Professor Sharpe said the projection was for the rates to plateau by 2015 and he expected they might then rise. The blood-pressure reversal, linked to the obesity epidemic, was "a really bad mix. This provides justification, if we needed it, for stronger preventive measures particularly for heart health and diabetes checks".
Dr McLean said the blood pressure results demonstrated the need for a return to healthy-eating policies discarded by the National Government, a reduction in GST on fruit and vegetables and the British-style publication of targets to encourage the food industry to reduce salt content.
In 2008/9 Mew Zealand adults ate 9g a day, unchanged from a decade earlier and well above the recommended maximum intake of 5.8g.
Under pressure
31 per cent of adults have abnormally high blood pressure
15 per cent report taking drugs to reduce blood pressure
35-54 year-old NZ Europeans and others - average blood pressure up since 2002
35-74 year-old Maori - average blood pressure up since 2002
Source: Otago University and 2008/9 Adult Nutrition Survey
By Martin Johnston Email Martin