Obesity Epidemic Fueling Spike in Hypertension
In December 2012, the Obesity Society and the American Society of Hypertension Issued a Position Paper titled "Obesity-Related Hypertension: Pathogenesis, Cardiovascular Risk, and Treatment," which was published in both society journals, Obesity and The Journal of Clinical Hypertension. [Landsberg et al, 2012; Landsberg et al, 2013] The paper grew out of increasing concern about the "very real obesity epidemic" currently facing the United States. According to the most recent National Health and Nutrition Examination Survey (NHANES), approximately 149.3 U.S. adults can be classified as either overweight or obese (BMI >25), [AHA, 2012] and a third of U.S. adults are obese (BMI >30). [Ogden et al, 2012] The frequent co-occurrence of obesity and hypertension suggests that rising obesity rates are related to rising rates of hypertension; indeed, at least 75 percent of hypertension incidence is estimated to be directly associated with obesity. [Landsberg et al, 2013]
Below, Lewis Landsberg, MD, Irving S. Cutter Professor of Medicine and Director of the Northwestern Comprehensive Center on Obesity at the Feinberg School of Medicine, Northwestern University, Chicago, IL, and lead author of the position paper, comments on its salient teaching points.
What motivated the Obesity Society and the American Society of Hypertension to commission a position paper on obesity and hypertension?
Our goal was to raise awareness among members of both societies as well as other clinicians regarding the urgency of understanding and addressing the relationship between weight and blood pressure (BP) and the constellation of cardiovascular risk factors that travel together with obesity. Obesity and hypertension each independently increases the risk of cardiovascular and renal disease as well as type 2 diabetes. Coexisting obesity and hypertension present an even greater risk of both morbidity and mortality. We wanted clinicians to understand that it is not sufficient to treat hypertension without treating obesity as well.
What accounts for the high comorbidity of obesity and hypertension?
There are several purported mechanisms of the pathogenesis of obesity-related hypertension. Obesity is associated with hyperinsulinemia, and insulin plays a role in hypertension via its stimulation of the sympathetic nervous system. Increased levels of circulating leptin, a polypeptide produced in adipocytes and secreted into plasma, also stimulates the SNS. The renin-angiotension-aldosterone system (RAAS) is activated in obesity and contributes to hypertension. Additionally, obese hypertensive individuals display increased salt sensitivity, due to the impact of obesity on the kidneys' sodium reabsorption patterns.
How does pharmacologic treatment of hypertension in obese patients differ from its treatment in the non-obese?
In obese patients, more attention must be paid to the impact of antihypertensives on metabolic abnormalities. For example, diuretics and b-blockers have potentially adverse eff ects on insulin resistance and lipid metabolism and should be avoided if possible, or at least should be used with caution and under very specific circumstances. Instead, angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), which target the RAAS system, should be used as first-line agents, since this system is over-expressed in obesity. ACE inhibitors and ARBs are not associated with weight gain or insulin resistance, and may provide renal protection as well. Calcium channel blockers are effective and metabolically neutral, so they are viable options with no contraindications.
Bariatric agents may have utility in inducing weight loss. Orlistat, which inhibits gastrointestinal lipases, thereby decreasing the absorption of dietary fat, has been associated with statistically significant weight loss. However, studies have not shown it to have significantly direct impact on hypertension. Phentermine, which is approved by the Food and Drug Administration (FDA) for very short-term treatment of obesity, may be contraindicated in hypertension, due to its potential for elevating BP.
Obese hypertensive patients with diabetes may benefit from several FDA-approved medications such as metformin and the incretins, which have been associated with weight loss as well as reduced BP.