Many of us are familiar with the condition called white coat hypertension in which people experience high blood pressure in the doctor's office because of anxiety or stress – but do not actually have hypertension. The reverse of white coat hypertension is masked hypertension. And it is dangerous condition.

Masked hypertension -- blood pressure that's normal at the doctor's office but elevated out of the office -- is just as dangerous as regular hypertension, according to a study in the American Journal of Hypertension (volume 20, page 385).

The study looked at 282 people who were not taking antihypertensive medication but who had at least one risk factor for cardiovascular disease, for example, hypertension, diabetes, high cholesterol, kidney disease, or smoking.

The researchers found that participants with masked hypertension had signs of damage to their arteries. For example, they had more thickening of the carotid artery than people with sustained hypertension (high blood pressure at the doctor's office and at home), white coat hypertension (high blood pressure at the doctor's office but not at home), or normal blood pressure (both at the doctor's office and at home). They also had stiffer arteries than people with white coat hypertension or normal blood pressure. Thus, masked hypertension is not a benign condition.

Your doctor will suspect masked hypertension if your blood pressure is normal or high-normal at the doctor's office but you have multiple cardiovascular risk factors. There's not yet evidence that medication will reduce the risks of masked hypertension, so aggressive lifestyle measures -- restricting alcohol, losing weight, exercising, quitting smoking, and reducing salt intake -- are the best approach.