Do Narrowed Blood Vessels Lead to Hypertension?

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The summary below is from the full report titled "Retinal Arteriolar Diameter and Risk for Hypertension." It is in the 17 February 2004 issue of Annals of Internal Medicine (volume 140, pages 248-255). The authors are T.Y. Wong, R. Klein, A.R. Sharrett, B.B. Duncan, D.J. Couper, B.E.K. Klein, L.D. Hubbard, and F.J. Nieto, for the Atherosclerosis in Communities Study.

What is the problem and what is known about it so far?

Hypertension is persistent high blood pressure. It is one of the most common chronic conditions in adults in the United States. Persistent high blood pressure strains the heart and harms arteries (vessels that carry blood away from the heart). It increases the risk for blindness, heart attack, heart failure, kidney problems, and stroke. The underlying cause is unknown in most patients, but most people with hypertension have narrowed arteries. Some researchers think that narrowing of small arteries (arterioles) may cause high blood pressure. Others think that the high blood pressure itself causes narrowing of small arteries.

Why did the researchers do this particular study?

To see if narrowing of the small arterioles in the retina (the layer of tissue covering the back inside wall of the eye) precedes the development of high blood pressure.

Who was studied?

5628 adults 49 to 73 years of age. None met criteria for high blood pressure (blood pressure 140/90 mm Hg) when they were first examined.

How was the study done?

Researchers examined middle-aged adults from 4 locations in the United States from 1987 to 1989. They measured blood pressure carefully, took blood samples for cholesterol levels, and asked questions about medical history and health behaviors. The researchers repeated these assessments at 3-year intervals 3 times (total of 4 assessments). At the third assessment, they took digital pictures of the retinas of the patients and measured the size of the vessels on the photographs. They then looked at people who developed high blood pressure between the third and fourth assessments to see how often people with and without narrowed retinal vessels developed high blood pressure. These analyses "controlled for" other factors, such as age, sex, smoking status, diabetes, cholesterol level, and blood pressure level, that might be associated with increased risk for developing high blood pressure.

What did the researchers find?

About 14% of the adults developed hypertension between the third and fourth visits. More of the adults with narrowed arterioles developed high blood pressure than did those without any narrowed arterioles.

What were the limitations of the study?

None of the participants met criteria for hypertension when they had their eye photographs. However, several had had borderline high blood pressure readings in the past. It is difficult to determine whether some of these people actually already had early hypertension.

What are the implications of the study?

Narrowed arterioles may precede the development of hypertension. However, whether the narrowed arteries mark elevated blood pressure in persons not yet meeting criteria for hypertension rather than cause the hypertension is still unclear.