SUNDAY, Jan. 29 (HealthDay News) -- People whose systolic blood pressure -- the upper number in their reading -- is different in their left and right arms may be suffering from a vascular disease that could increase their risk of death, British researchers report.

The arteries under the collarbone supply blood to the arms, legs and brain. Blockage can lead to stroke and other problems, the researchers noted, and measuring blood pressure in both arms should be routine.

"This is an important [finding] for the general public and for primary care doctors," said Dr. William O'Neill, a professor of cardiology and executive dean of clinical affairs at the University of Miami Miller School of Medicine.

"Traditionally, most people just check blood pressure in one arm, but if there is a difference, then one of the arteries has disease in it," he said.

The arteries that run under the collarbone can get blocked, especially in smokers and diabetics, he noted. "If one artery is more blocked than the other, then there is a difference in blood pressure in the arms," O'Neill explained.

"Doctors should, for adults -- especially adult smokers and diabetics -- at some point check the blood pressure in both arms," he said. "If there is a difference it should be looked into further."

The report appears in the Jan. 30 online edition of The Lancet.

For the study, a team led by Dr. Christopher Clark, from the Peninsula College of Medicine and Dentistry at the University of Exeter in Devon, England, reviewed 28 studies that looked at differences in systolic blood pressure between arms.

This process is called a meta-analysis. It uses data from previously published studies to find trends that may not have surfaced in the original data.

This analysis found that a difference of 15 millimeters of mercury (mm Hg) or more between readings was linked with an increased risk of narrowing or hardening of the arteries supplying the lower limbs, called peripheral vascular disease.

The risk of reduced blood flow to the legs and feet was increased 2.5 times and the risk of decreased blood flow to the brain was increased 1.6 times, the researchers found.

The difference in blood pressure was also associated with a 70 percent increased risk of dying from cardiovascular disease and a 60 percent increased risk of death from any cause, the authors added.

The risk of having peripheral vascular disease was also increased with a 10 mm Hg difference in blood pressure between arms, the researchers noted.

It makes no difference which arm has the higher or lower pressure, it's the difference between them that matters, the study authors said.

Finding peripheral vascular disease early and treating it by lowering blood pressure and cholesterol as well as giving up smoking can help reduce the risk of death, Clark's group said.

"Our findings suggest that a difference in [systolic blood pressure] of 10 mm Hg or more, or 15 mm Hg or more, between arms could identify patients at high risk of asymptomatic peripheral vascular disease and mortality who might benefit from further assessment," the researchers concluded.

"Findings from our study should be incorporated into future guidelines for hypertension [high blood pressure] and blood pressure measurement," they added.

Another expert agreed that when it comes to blood pressure monitoring, both arms matter.

"These findings further reinforce blood pressure measurement guidelines of the American Heart Association, World Health Organization, International Society of Hypertension and European Society of Hypertension, which recommend that blood pressure should be measured in both arms at initial assessment," said Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, and spokesman for the American Heart Association.

He believes that, "individuals found to have differences in systolic blood pressure in between arms of greater than 10 or 15 mm Hg should undergo further vascular assessment."

More information

For more information on high blood pressure, visit the American Heart Association.