Q: How important is control of obesity in the treatment of hypertension?
A: I suspect that this question often arises in discussions of hypertension management because of the frequent failure of clinicians' efforts to encourage obese patients with hypertension to lose weight--and the resulting frustration. The age-adjusted prevalence of obesity (body mass index [BMI], 30 kg/m2 or higher) has increased to 31% in the United States. The percentage of overweight persons (BMI, 25 to 29) and obese persons has increased to 65%. Half of African Americans are obese and more than 80% are overweight. Obesity is an increasingly prevalent risk factor for hypertension.1
The prevention of hypertension in persons at increased risk because of genetic or adverse environmental factors (such as smoking, progressive weight gain/obesity, and excessive alcohol use) has not been clearly documented in major clinical trials. However, a number of smaller studies have reported that targeted nonpharmacologic strategies--including weight loss--can prevent the progression from prehypertension (120 to 129 mm Hg systolic and 80 to 99 mm Hg diastolic) to overt hypertension (above 140/90 mm Hg).2,3 These strategies are outlined in the most recent report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) (Table).1
Other consequences of obesity. In addition to hypertension, obesity is associated with an increased prevalence of stroke, coronary artery disease, chronic respiratory diseases, gallbladder disease, and renal insufficiency. The 10-year risk of hypertension, heart disease, or stroke in persons with a BMI of 30 or higher is 3.8, 2.2, and 2.1 times, respectively, that of persons with a BMI below 22. The odds that diabetes mellitus will develop are 18 times greater in persons whose BMI is higher than 30, and 51 times greater in those with a BMI above 35.4
The metabolic syndrome. As the BMI increases, there is also clear evidence of a clustering of cardiovascular risk factors, known as the metabolic syndrome. According to the World Health Organization, this syndrome consists of hyperinsulinemia or a fasting plasma glucose level of 110 mg/dL or higher, plus 2 or more of the following:
•A waist-to-hip ratio greater than 0.9, or a BMI of 30 or higher.
•A triglyceride level of 150 mg/dL or higher.
•A high-density lipoprotein cholesterol level lower than 35 g/dL.
•Blood pressure (BP) of 140/90 mm Hg or higher.5
Advantages of weight loss. Depending on the degree of overweight or obesity, it is possible to control BP to below 140/90 mm Hg in some patients who do not lose weight. However, this will likely require an increased number of medications and/or increased dosages. Studies of weight loss have shown some reduction in BP even when the absolute weight loss is small--that is, as little as 10 to 12 lb. (This is an important point to stress to patients.) The greater the weight loss, the greater the reduction in BP, which translates into fewer antihypertensive medications and/or lower dosages.
Even more important, obese patients or those with the metabolic syndrome have other risk factors that must also be aggressively managed to reduce the potential for morbidity and mortality. Significant weight reduction helps control insulin resistance and diabetes mellitus; lower BP; normalize lipid levels; and reduce the risk or the severity of osteoarthritis, gout, and biliary disease. Multiple risk factor control can also inhibit the progression of accelerated atherosclerosis to prevent future cardiovascular morbidity and mortality.
Obstructive sleep apnea, obesity, and hypertension. More than 50% of patients with hypertension have some evidence of obstructive breathing, particularly during sleep. Obstructive sleep apnea (OSA) independently increases the risk of hypertension, insulin resistance, and cardiovascular morbidity. Nevertheless, OSA remains undetected in up to 80% to 90% of patients with obesity and hypertension. OSA is even more prevalent in obese persons who have hypertension that is refractory to treatment and in those with evidence of loss of the nocturnal dipper effect on 24-hour ambulatory BP monitoring.
A high index of suspicion for OSA is required in the evaluation of an obese patient with hypertension. Several simple questions may suggest the diagnosis: Does the patient snore at night? Does he or she complain of daytime drowsiness? Has a spouse or other family member noted apneic episodes when the patient is asleep?
Polysomnography is now widely available to help establish the diagnosis. Most studies suggest that treatment with continuous positive airway pressure lowers BP in obese hypertensive patients with OSA and usually reestablishes the nocturnal dipper effect. Significant weight loss represents a critical component of treatment; it reduces the frequency of apneic episodes and may improve hypertension, lipid metabolism, and insulin resistance.6
1. Chobanian AV, Bakris GL, Black HR, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report. JAMA. 2003;289: 2560-2571.
2. Greenlund KJ, Croft JB, Mensah GB. Prevention of heart disease and stroke risk factors in persons with prehypertension in the United States, 1999-2000. Arch Intern Med. 2004;164:2113-2118.
3.Russell LB, Valiyeva E, Carson JL. Effects of prehypertension on admissions and deaths: a simulation. Arch Intern Med. 2004;164:2119-2124.
4. Field AE, Coakley EH, Must A, et al. Impact of overweight on the risk of developing common chronic diseases during a 10-year period. Arch Intern Med. 2001;161:1581-1586.
5. World Health Organization. Definition, Diagnosis, and Classification of Diabetes Mellitus and Its Complications: Report of a WHO Consultation. Part 1: Diagnosis and Classification of Diabetes Mellitus. Geneva: World Health Organization; 1999.
6.Vidt DG. When snoring has more ominous consequences than a sleepless spouse. Consultant. 2003;43: 1410-1412.
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