Obesity Raises Prehypertensives' Risk

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Obese patients with prehypertension are increased risk of progressing to end-stage renal disease (ESRD) and death from CKD, according to researchers in Norway.

John Munkhaugen, MD, a research fellow at the Norwegian University of Science and Technology in Trondheim, and colleagues linked data on 74,986 adults participating in the first Health Study in Nord-Trøndelag (HUNT I) to the Norwegian Renal Registry and Cause of Death Registry. The main outcome measure was treated ESRD or CKD-related death.

At baseline, the cohort had a mean systolic BP of 136.8 mm Hg and a mean BMI of 25.2 kg/m2; 49% had hypertension (BP higher than 140/90 or treated BP) and 35% had prehypertension (systolic BP of 120-139 mm Hg or diastolic BP of 80-89 mm Hg).

During a median follow-up of 21 years, 507 men (1.4%) and 319 women (0.8%) initiated renal replacement therapy (157 subjects) or died from CKD (669 subjects). The risk associated with body weight started to increase from a BMI of 25. In subjects with BP less than 120/80 mm Hg, risk did not increase with rising BMI, the investigators reported in the American Journal of Kidney Diseases (2009;54:638-646).

Among prehypertensive subjects, those with a BMI of 30-34.9 and 35 or greater had a 2.66 and 5.94 times increased risk of the main outcome compared with subjects whose BP was less than 120/80 and who had a BMI of 18.5-24.9, after adjusting for numerous potential confounders. For prehypertensive subjects with a BMI of 18.5-24.9 and 25-29.9, the risk increased nonsignificantly by 21% and 10%, respectively.

Among hypertensive subjects, those with a BMI of 18.5-24.9, 25-29.9, 30-34.9, and 35 and greater had a 2.1, 2.4, 3.3, and 5.5 times increased risk compared with participants who had a BP less than 120/80 and BMI of 18.5-24.9.

“Our results for the joint effect of BP and BMI on kidney dysfunction might have important clinical implications regarding the debate about treatment of people with increased risk of kidney disease,” the authors wrote.

The finding that the future risk of treated ESRD or CKD-related death increased substantially among individuals with near-normal BP with increasing body weight can be important for guiding treatment of patients with prehypertension, the researchers noted.

They suggest that obese prehypertensive individuals should be considered for a stricter BP goal, as with patients with diabetes and CKD.

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