THURSDAY, March 9, 2006 (HealthDay News) -- Levels of unhealthy blood pressure are on the decline worldwide, a new study shows, but experts aren't sure why.
In a large population-based study encompassing 38 populations in 21 countries across four continents, including the United States, researchers have found that overall blood pressure has fallen by more than 2 mm/Hg over a 10-year period.
However, the finding is not due to an increased use of antihypertensive medications, the experts said.
"There is a lot more to health than popping pills," said study author Dr. Hugh Tunstall-Pedoe, a professor of cardiology and epidemiology at Ninewells Hospital & Medical School, in Dundee, Scotland. "There is a greater dimension to blood pressure and its control than simply a prescription of medication."
The results, culled from a World Health Organization study, appear in the March 9 online edition of the British Medical Journal.
The researchers wanted to find out if this overall drop in blood pressure was due to the use of blood pressure medications. Since blood pressure dropped across the spectrum of blood pressure levels, they concluded that the decline could not be caused by blood-pressure-lowering medications, which are usually only taken by patients with dangerously elevated readings.
"We showed that low blood pressure and mid-blood-pressure readings came down as much as high blood pressure readings in these populations," Tunstall-Pedoe explained.
In data collected from the mid-1980s to mid-1990s, the researchers found that, on average, blood pressures dropped by 2.26 mm/Hg. Declines were more pronounced in women than in men.
The trend "appears to be due to a mass population effect rather than physician interference," Tunstall-Pedoe said. "We cannot hang our hat on any particular explanation."
One expert is puzzled by the findings, but speculated that blood pressures are dropping because of better diets and medical care.
"Those of us who engage in lifestyle counseling might be inclined to pat ourselves on the back over these findings," said Dr. David L. Katz, an associate professor of public health and director of the Prevention Research Center at the Yale University School of Medicine.
Perhaps attention to diet and physical activity is paying off, he said. On the other hand, "if it were, we might be seeing declines in obesity and insulin resistance," Katz said. However, "the trends there are clearly going the other way," he noted.
He suspects that other public health interventions, such as increasing consumption of foods fortified with folate, calcium and other key nutrients, may be partly responsible. In addition, agricultural trends that make fruits and vegetables available year-round may be contributing as well.
"In some populations, increasing restrictions on tobacco use may be another factor," Katz said. "And while the overall trend cannot be explained by medication use, certainly the declines in the elevated blood pressure values are partly due to better medical care."
The good news is that blood pressure levels appear to be declining in many countries, which should mean reduced risks for heart attack and stroke, Katz said. "But, we don't really yet know how to explain the good news," he said.
For more on preventing and controlling high blood pressure, head to the American Heart Association.