Screening for Hypertension

Hypertension ranks among the most important of conditions to screen for in adult primary care practice, given its prevalence, ease of detection, associated cardiovascular morbidity and mortality, and effectiveness of treatment. The size of the affected population is staggering—according to the latest National Health and Nutrition Examination Survey (NHANES), 29.0% of adults in the United States have hypertension. Among those over the age of 60 years, the prevalence rises to over 66%. National health policy programs such as the U.S. Healthy People initiative include hypertension control as a prime target. Over the last 40 years, efforts to educate both physicians and the general public about the importance of identifying and treating high blood pressure and the improved options for treatment have resulted according to the NHANES data in improved awareness (80.7%, up from 69.1%), improved blood pressure control (50.1%, up from 27.3%), and a significant decrease in morbidity and mortality from cardiovascular disease and stroke. Despite this progress, there is still much room for improvement, given the absolute number of persons affected and suboptimal rates of control, especially among youngeraged aged persons (18 to 39 years), the elderly (>60 years), and selected populations such as Hispanics. Interestingly, lack of access to health care has not been identified as a prime factor in suboptimal control; in most instances it occurs, as one observer noted, “under the watchful eye of the health care system.” It behooves all primary care health professionals to be versed in well-screening for hypertension. This chapter focuses on screening for hypertension (see also Chapters 19 and 26 for evaluation and management, respectively).

EPIDEMIOLOGY AND RISK FACTORS FOR THE DEVELOPMENT OF HYPERTENSION (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15)

Epidemiology

As noted, prevalence of hypertension among US adults is currently estimated at 29.0%, rising with age to 66% in those greater than 60 years old. With increasing age, systolic hypertension becomes increasingly prevalent, accounting for the majority of cases by age 50. Diastolic hypertension is the more common form in patients under the age of 40 years. Approximately 70% fall into stage 1 (diastolic blood pressure [DBP] 90 to 99, systolic blood pressure 140 to 159 mm Hg), as defined by the Joint National Committee on Prevention, Detection, Evaluation, and Management of High Blood Pressure.

Major Risk Factors

Age

Systolic and DBPs rise steadily with age into the fifth and sixth decades, when the rate of increase levels off. By then, the prevalence of hypertension approaches 50%. The lifetime risk for developing hypertension in individuals older than 55 years is 90%. The cardiovascular event risk associated with hypertension rises steadily with age. For individuals older than 50 years of age, the systolic pressure is the better predictor of such risk; under the age of 50, diastolic pressure best correlates with the risk. In the elderly, pulse pressure (the difference between systolic and diastolic pressures) is an independent predictor of cardiovascular disease.

Gender

Men in all age groups have a higher prevalence of hypertension than women. In the third and fourth decades, it is more than twice as common among men as among women. The ratio decreases with advancing age, so that by age 60 years, there is only a slight male predominance. Men have substantially higher complication rates than women until 5 to 10 years after menopause, when the rates become similar. The Framingham Study demonstrated that for the major complications of hypertension, the risk of developing cardiovascular complications in mildly hypertensive women approximately equals that of normotensive men. The postulated mechanisms for this reduced risk in women include the beneficial effects of estrogen on vasculature and the different hemodynamic profile of premenopausal hypertensive women, which includes a lower peripheral resistance and higher cardiac output. After menopause, estrogen levels fall, the hemodynamic profile shifts to one of high peripheral resistance and normal cardiac output, and by age 70 years, the incidences of stroke and coronary disease in women approach those of men.

Race

There is a marked increase in the prevalence of hypertension among African Americans. Compared with whites, the overall prevalence ratio is 2:1. It is higher in young adults and lower in the elderly. Severe hypertension occurs nearly five times more often than in whites. In addition, the complication rate for any given blood pressure is significantly higher. For example, compared with white hypertensive patients, African Americans have an 80% higher mortality from stroke, a 50% higher mortality from heart disease, and a 320% higher incidence of endstage renal failure. Whether this represents as-yet undefined differences in the underlying pathophysiology of hypertension in African Americans or inadequate access to medical care is unclear, although it is likely that both factors play a role.

Obesity

The prevalence increases in obese patients, as does the prevalence of hyperlipidemia and type 2 diabetes mellitus. The association of these three conditions has been attributed to the presence of relative insulin resistance, which may cause hypertension in some patients (see Chapter 19). Data from the Nurses’ Health Study demonstrated that women who gained more than 20 lb after age 18 years had a fivefold increase in the risk of developing hypertension compared with those who did not gain weight. Conversely, women who were at higher body mass index levels at age 18 years and lost 5 to 10 lb had about half of the risk of developing hypertension. In a recent study of short-term predictors of increases in blood pressure, a weight gain of 5% or an increase in waist circumference of 1 inch or more was associated with a significant increase in blood pressure. In addition, obesity is associated with the development of obstructive sleep apnea, another independent risk factor for the development of hypertension.

Other Risk Factors

Hypertension is much more likely to occur in patients with a positive family history. It is increasingly clear that hypertension may be caused by a variety of genetic mutations. In addition, environmental factors affect the onset and severity of hypertension. Increased salt intake correlates with increased prevalence in large populations, although not in individuals. An individual’s prior or current salt intake per se is not a predictor of blood pressure level. Alcohol intake in excess of 2 oz/d is linked to hypertension. This appears to be related to alcohol’s ability to stimulate the release of corticotropin-releasing factor from the hypothalamus, which increases central nervous system sympathetic activity, causing a rise in blood pressure. Caffeine intake may cause an acute increase in blood pressure but does not appear to affect the prevalence of hypertension generally. Sedentary lifestyle has been associated with an increase in the risk of developing hypertension. The role of psychological stress and its concomitant sympathetic stimulation appears to be variable and possibly a function of underlying differences in susceptibility. Cigarette smoking, an important risk factor in its own right, is not positively associated with increased blood pressure, but hypertensive smokers are at significantly greater risk of developing cardiovascular complications than are hypertensive nonsmokers.

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