Losing weight and cutting salt consumption could keep thousands of Americans from developing high blood pressure or its potentially fatal complications, scientists said yesterday. But reducing stress appeared to have no effect on blood pressure.
Scientists finishing the nation's largest study into non-drug methods of blood pressure control said people don't have to make drastic changes in what they eat to realize profound benefits.
In a study involving 2,182 men and women at the Johns Hopkins School of Hygiene and Public Health and 10 other medical centers, volunteers significantly reduced their blood pressure simply by losing an average of 8 1/2 pounds and exercising, or by shaving 2 1/2 grams of salt off their average daily intake of 9 1/2 grams.
"We're talking about really modest changes in weight, modest ++ changes in sodium intake," said Dr. Paul Whelton, the chief investigator who is a professor of epidemiology at the Johns Hopkins School of Hygiene and Public Health.
Other studies had suggested that stress reduction might not help people reduce lower their blood pressure, Dr. Whelton said. But the notion remained popular among the public.
This study, described in today's Journal of the American Medical Association, may settle the issue.
"We all think we're stressed out and that's the cause of a lot of disease, and maybe it is," Dr. Whelton said. But he said volunteers assigned to a stress-reduction program received regular counseling from leading experts in relaxation techniques. And while they may have felt more at ease, their blood pressure didn't dip at all.
But Dr. W. Gordon Walker, a professor of medicine at the Johns Hopkins School of Medicine, said it is still possible that a small segment of the population -- a segment that has yet to be identified -- can lower their blood pressure through relaxation.
The 18-month study focused solely on people with "high-normal" blood pressure: those who are not considered hypertensive but are on the verge of becoming so. The aim was to see if such people could lower their blood pressure without taking the traditional drugs used for this purpose.
An estimated 80 million to 89 million adults fall into the "high-normal" range.
Hypertension is considered one of America's most serious health problems, afflicting an estimated 20 percent to 35 percent of the adult population. It is a major risk factor in heart disease, kidney disease and stroke.
Volunteers in the study were all healthy, with diastolic blood pressures (the second number in a blood pressure reading) between 80 and 89. Readings of between 90 and 115 signify "borderline" hypertension, while readings above 115 signal true hypertension.
Many of the volunteers were assigned to different groups in which they were counseled to reduce their stress, weight or salt. Others were asked to take dietary supplements of calcium, magnesium, potassium or fish oil -- supplements that have won popularity among some physicians.
Others were asked to make no changes at all.
Only two groups saw significant reductions in their blood pressure: People in the weight-loss group lowered their blood pressure by an average of 2.3 points, while those in the salt-reduction group saw their pressure dip by about one point.
While the pressure changes may seem paltry, a two-point reduction across the general population could bring significant benefits. "We could expect about a 6 percent reduction in stroke mortality each year, and 4 percent reduction in coronary heart disease mortality," Dr. Whelton said.
"Those are big changes. Much disease comes from people at the lower levels of blood pressure, the high-normals. But they're not truly normal. They're inappropriately high."
In a subsequent study, just under way, scientists will see what happens if people can keep their weight and salt intake down over a longer period of time -- three years or more. Results of the two studies may prompt the National Heart Lung and Blood Institute, which sponsored the study, to issue new health recommendations to the American public.
If the advice is to lower salt consumption, Americans may need help from the food industry. Avoidance of the obvious offenders like potato chips, pickles and processed meats isn't enough, said Dr. W. Gordon Walker, a professor of medicine at the Johns Hopkins School of Medicine.
Breads and cereals carry hefty doses of sodium -- not just in added table salt, but also in the baking powders used to make dough rise.
Lower blood pressure without drugs
A major, new study compared these non-drug ways of lowering the blood pressure of people in the high-normal* "range:
Produced 'significant' improvement
Modest weight reduction
Losing about 8lbs. lowered diastolic blood pressure an average of 2.3 points; recommended exercise was 45 min. of brisk
walking, four or five times a week.
Eating, drinking less sodium
A diet with moderately reduced salt lowered diastolic blood pressure an average of 0.9 points
'Little evidence' of effect
No Significant improvement after weekly relaxation and stress management sessions, even in people who followed program carefully
No significant improvement from daily doses of calcium, magnesium, potassium and fish oil.
* Diastolic pressure of 80-89 (the diastolic is the second of the two numbers in a blood pressure reading, for example "140 over 82")