Common causes of hypertension
Stress, white-coat hypertension, and white-coat effect Emotional and physical stress is a common entity with associated health effects, specically in causing hypertension and cardiovascular disease. An interesting study that illustrates this compares the health of nuns in a secluded order with that of women in their local community. Lower blood pressure and decreased incidence of cardiovascular disease in the secluded nuns was noted,1 likely in part due to their comparatively peaceful lifestyle. Another study showed blood pressure in four population centers in the United States to be signicantly elevated in the months following the 9/11 terrorist attacks,2 again an effect associated with heightened anxiety and stress. Job strain3 and a sense of time urgency and hostility4 also have been associated with the development of hypertension and cardiovascular disease. The mechanism whereby stress causes hypertension is primarily due to enhancement of the sympathetic nervous system, although activation of the renin-angiotensin-aldosterone system (RAAS),5 salt retention,6 and endothelial dysfunction7 also occur. The degree of responsiveness to an acute stressor is also an important factor. Responsivity to stress is measured by the degree of blood pressure and heart rate increase, and the amount of time needed for these parameters to return to their respective baselines. Prolonged responsivity is strongly associated with future development of hypertension.8 Stress responsivity is also associated with white-coat effect and white-coat hypertension.9 The denition of white-coat effect is an increase in blood pressure that occurs during an exam by a physician-hence the term “white coat”—that can manifest in people with or without hypertension, whereas white-coat hypertension is dened as an elevated ofce blood pressure but a normal 24-hour ambulatory or home blood pressure. The precise denition of white-coat hypertension differs slightly depending on the guideline. For example, the European Society of Hypertension requires an ofce blood pressure of 140/90 mm Hg or greater, a normal 24-hour mean ambulatory blood pressure of <125-130/80 mm Hg, and a normal mean daytime blood pressure of <130-135/85 mm Hg.10 A normal mean home blood pressure of <135/85 mm Hg also can be used. White-coat effect is nicely
illustrated in an Italian study that showed an increase in blood pressure of 22/16 mm Hg when initially measured by a male physician.11 After 10 minutes, repeat blood pressure decreased to a plateau level but was still 12/8 mmHg above baseline. White-coat hypertension is more prevalent in certain populations, occurring in 38% of Finnish hypertensive people,12 whereas 20% is typical in Western society.13 As many studies suggest only a minimal increase in cardiovascular risk from white-coat hypertension,14 most guidelines do not recommend treatment with drug therapy unless there is evidence of organ damage or other signicant cardiovascular risk factors. Lifestyle changes such as a low-salt diet and weight loss are recommended rst. However, there is evidence suggesting a less benign nature as white-coat hypertension may be associated with cardiac hypertrophy,15 cardiovascular disease,16 and stroke.17 There also is a signicant risk of progressing from white-coat hypertension to overt hypertension.18 Perhaps, it is best to view white-coat hypertension as an intermediate hypertensive state that needs careful monitoring.