Diabetes and hypertension combo invite silent stroke

American Heart Association
Friday, 19 September 2003

Having diabetes along with high blood pressure dramatically raises the risk of brain lesions known as "silent strokes," researchers report in today's rapid access issue of Stroke: Journal of the American Heart Association.

Silent strokes occur when smaller blood vessels in the brain become blocked. Although they don't cause classic stroke symptoms, such as sudden headache, dizziness or loss of motor skills, multiple silent strokes – also called silent cerebral infarcts (SCIs) – increase the risk for a future stroke.

"Silent cerebral infarcts are markers of hypertension-related brain damage and asymptomatic stroke," said lead author Kazuo Eguchi, M.D., of the department of cardiology at Jichi Medical School in Tochigi, Japan. "In addition to the stroke risk, there is increasing evidence that multiple SCIs are closely associated with cognitive problems, vascular dementia and partly associated with Alzheimer's disease," Eguchi explained.

Researchers performed brain magnetic resonance imaging (MRI) and 24-hour blood pressure monitoring on 360 Japanese patients (134 men and 226 women, average age 67) with high blood pressure (hypertension) but no symptoms. Of these, 159 also had diabetes. None of the patients had been diagnosed with other cardiovascular diseases.

The researchers monitored each patient's blood pressure for 24 hours while they were off medication and taking part in normal weekday activities. Patients wore a blood pressure cuff that automatically inflated and recorded blood pressure and pulse every 30 minutes.

Brain MRIs were examined for the presence of silent cerebral infarcts, visible as blockages in small arteries leading to deep white matter in the brain.

Evidence of silent strokes was detected in 82 percent of patients with diabetes and hypertension and in 58 percent of those with hypertension alone. Three or more SCIs were found in 62 percent of patients with diabetes and hypertension and in 35 percent of those with hypertension alone.

Participants were significantly more likely to have one or more SCIs if they were older, had diabetes, and had suffered hypertension for 10 years or more. In addition, being male, or having a higher systolic blood pressure during monitoring made participants significantly more likely to have multiple SCIs.

"If a patient is found to have multiple SCIs, aggressive blood pressure control is essential and the patient should be treated as if they have already had a clinical stroke," Eguchi said. This may include taking anti-platelet medications (such as aspirin) or anti-coagulants (such as warfarin) to interfere with the blood's ability to clot, as well as monitoring for blockage in the large carotid neck arteries that carry blood to the brain.

The researchers also investigated the silent stroke risk in patients with "white-coat" hypertension – those with elevated blood pressure readings in the doctor's office (greater than 140/90 millimeters of mercury [mmHg]) but blood pressure of less than 135/80 mmHg during ambulatory blood pressure monitoring.

Participants with diabetes and white-coat hypertension had more silent cerebral infarcts (an average of 2.8 per person), while those with sustained high-blood pressure but no diabetes had fewer (an average of 2.3).

Patients with diabetes and sustained high blood pressure had the most SCIs (an average of 5.2). Patients with white-coat hypertension and no diabetes had the fewest (an average of 1.4).

"Hypertension-related organ damage was more advanced in diabetic patients. This means that blood pressure control is very important for diabetic patients, even those who just have white-coat hypertension," said Eguchi.

When treating hypertension in people with diabetes, the goal is a blood pressure less than 130/80 mmHg, suggests the American Heart Association and the Joint National Committee Report on the Treatment of High Blood Pressure, issued in May 2003. Between 40 percent and 60 percent of people with diabetes have high blood pressure, according to the American Heart Association.

People with high blood pressure who don't already have diabetes should be vigilant in taking steps to avoid it, such as controlling weight, eating a healthy diet and exercising regularly, Eguchi said.

"I recommend that all hypertensive patients take an oral glucose tolerance test at least once a year to check for impaired glucose tolerance or insulin resistance," he said.

Co-authors are Kazuomi Kario, M.D., and Kazuyuki Shimada, M.D.

For more information, or to contact American Heart Association, see their website at: www.americanheart.org