By David Douglas

NEW YORK (Reuters Health) - White-coat hypertension is considered harmless in most people, but it appears to increase the risk of microvascular complications in patients with type 2 diabetes, Brazilian researchers report in Diabetes Care.

White-coat hypertension refers to the tendency for some patients who normally don't have high blood pressure to have a temporary increase in pressure while they are in their doctor's office.

Lead investigator Dr. Caroline B. Kramer told Reuters Health: "We believe that blood pressure levels are a strong predictor of chronic complications, and blood pressure should not be categorized only as normal or abnormal." Subtle changes such as white-coat hypertension or high-normal blood pressure should also be taken into account.

To examine the influence of white-coat hypertension, Kramer and her colleagues at Hospital de Clinicas de Porto Alegre identified 46 diabetic patients with blood pressures in the normal range during normal activity, but had elevated pressure in the office. These patients were compared with 117 patients who had normal blood pressure under both circumstances. None of the patients was taking antihypertensive medications.

While the groups did not differ in clinical characteristics or laboratory findings, the investigators report, the white-coat hypertensives had a higher average systolic blood pressure (the top number of a blood pressure reading) during daytime monitoring (126.6 versus 123.2 mm Hg) and during 24-hour ambulatory monitoring (124.7 versus 121.0 mm Hg).

After further analysis, they found that white-coat hypertension was associated with traces of protein in the urine and a nearly three-fold increased risk of developing diabetic retinopathy.

"Therefore," the investigators say, "white-coat hypertension should not be considered a harmless condition and treatment should be considered."

Kramer added that randomly assigned, double-blind studies are "needed to clarify a possible role of treating such conditions in type 2 diabetes mellitus."

SOURCE: Diabetes Care, December 2008.

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