Thomas Kahan    瑞典卡罗琳斯卡医学院
　　High blood pressure is globally the most important risk factor for premature death， both in the developing countries and in the developed parts of the world. Furthermore， the number of hypertensive subjects will increase， due an increasing global population and due to an increasing global rate of hypertension. Thus， it is estimated that there will be some 1.56 billion hypertensive subjects by the year 2025 globally.
　　The future risk for cardiovascular complications and death associated with hypertension (usually a blood pressure 140/90  mm  Hg or more) is well established. However， a blood pressure level of 130~139/80~89  mm  Hg， termed high-normal blood pressure or prehypertension or borderline hypertension， has also been demonstrated to confer an approximately two fold increased risk for future cardiovascular events. Of note， the blood pressure measured already during adolescence predicts future mortality. Furthermore， blood pressure tracking is strong， and childhood blood pressure is associated with blood pressure in adult life， suggesting that early intervention may be of importance.
　　Given this information， can early antihypertensive treatment actually prevent hypertension? Animal experiments have shown that early brief treatment with drugs that inhibit the renin-angiotensin-aldosterone system can prevent the development of high blood pressure later in life. In man， antihypertensive drugs given as secondary prevention following a cardiovascular event to patients with a high-normal blood pressure can reduce future cardiovascular mortality and all cause mortality.However， few studies have examined if antihypertensive drug treatment can prevent hypertension. There is some evidence to suggest that drug therapy given to subjects with a blood pressure of 130-140/80-90 mm Hg could delay the onset of hypertension， but no study to show that a brief period of drug treatment has any major effect in the prevention of  later development of hypertension.
　　In man， drugs blocking the renin-angiotensin-aldosterone system may delay incident hypertension. Properly designed studies to determine the efficacy of drug therapy in high-normal blood pressure on clinical outcome are needed. Lifestyle intervention is recommended as it improves cardiovascular risk profile， but drugs are more convenient and more likely to be adhered to than lifestyle modifications. Safety issues and cost effectiveness of long-term treatment in high-normal blood pressure need to be addressed. Until further evidence is revealed， assessment of global absolute risk should guide the decision to use antihypertensive drugs in subjects with high-normal blood pressure levels.