White-coat and masked hypertension significantly increased the risk of having sustained high blood pressure 10 years later, according to a study published in Hypertension: Journal of the American Heart Association.

In white-coat hypertension, a patient's blood pressure is high at the doctor's office but normal in everyday life. Masked hypertension refers to blood pressure that is normal when tested in medical settings but sporadically high when patients are out in the community.

Researchers followed 1,412 people, ages 25-74, who were part of the larger Pressioni Arteriose Monitorate e Loro Associazioni (PAMELA) study. PAMELA is the first study in which researchers took office blood pressure readings and used two different kinds of out-of-office testing: 1) ambulatory monitoring, in which the patient wears an automated blood pressure monitor that takes blood pressure at 20-minute intervals throughout a 24-hour period; and 2) home blood pressure monitoring, using portable home monitors to check blood pressure sporadically at home.

For the study, which was conducted at University Milan-Bicocca in Milan, Italy, researchers took one morning and one evening blood pressure reading. After the initial round of blood pressure testing, they re-tested subjects 10 years later to see how many patients from the normal blood pressure, white-coat hypertension and masked hypertension groups later developed sustained high blood pressure.

At the 10-year follow up, 42.6 percent of those who originally had white-coat hypertension and 47.1 percent of those in the masked hypertension group had developed sustained high blood pressure, compared to a much lower 18.2 percent in the group that had normal blood pressure in all settings at the study's start.

"After adjusting for age and gender, we found that compared to those who were normotensive at the start of the study, the risk of developing sustained hypertension was 2.51 times higher in patients with white-coat hypertension and 1.78 times higher in those with masked hypertension," said Giuseppe Mancia, M.D., lead author of the study and professor of medicine and chairman of the Department of Medicine at University Milan-Bicocca, S. Gerardo Hospital, Monza.
Doctors have long debated whether white-coat hypertension or masked hypertension are harmless or potentially dangerous.

"Earlier studies, all with shorter follow-up than this one, have been inconclusive," Mancia said. "This study is the first demonstration that white-coat hypertension and masked hypertension result in greater long-term risk of developing sustained hypertension, a major risk factor for heart attack and stroke. This means that these conditions are by no means clinically innocent, as they have often been thought to be."

Dan Jones, M.D., hypertension expert, past president of the American Heart Association and Vice Chancellor for Health Affairs and Dean of the School of Medicine at the University of Mississippi Medical Center in Jackson, said the study helped shed more light on a complex subject.

"This is a very well-designed study and very strong evidence that we need to pay attention to these various abnormal blood pressure patterns," Jones said. "I think this adds more weight to the understanding that people with intermittent elevations of blood pressure are more likely to become people with sustained hypertension."

Jones and Mancia said the study also indicates a role for home blood pressure monitors, which are cheaper than ambulatory monitoring and can provide information on blood pressure over long periods rather than for only 24 hours.

In an editorial published simultaneously, Franz H. Messerli, M.D. and Harikrishna Makani, M.D. said, "Mancia and colleagues have shown that over a 10-year period many patients relentlessly marched toward a more severe category of hypertension. However, for unknown reasons some patients are able to shake the spell and remain in the same blood pressure category or even go back to a category that confers a lesser morbidity and mortality. Our next challenge will be to identify clinical clues helping to predict in which direction our patients are prone to march."

Mancia's co-authors are Michele Bombelli, M.D.; Rita Facchetti, M.Sc.; Fabiana Madotto, M.Sc.; Fosca Quarti-Trevano, M.D.; Hernan Polo Friz, M.D.; Guido Grassi, M.D.; and Roberto Sega, M.D.

European Community, Sixth Framework program "InGenious HyperCare," partially funded the Mancia study.

GlaxoSmithKline, Novartis, Forest, Daiichi Sankyo and Boehringer Ingelheim funded the editorial.