Obesity Makes Kidneys More Vulnerable to Blood Pressure

With all the talk about obesity as a risk factor for diabetes and heart disease, we may often forget that excess weight affects all organ systems.

One set of organs that appears particularly sensitive to the ill-effects of excess weight are the kidneys.

This is nicely illustrated in a study just published in the American Journal of Kidney Disease by John Munkhaugen and colleagues from the Norwegian University of Science and Technology, Trondheim, Norway.

The researchers examined the combined effect of blood pressure (BP) and body weight on the risk for end-stage renal disease or chronic kidney disease (CKD)-related death.

Participants included data from 74,986 adults of the first Health Study in Nord-Trøndelag (88% participation rate), which were linked to the Norwegian Renal Registry and Cause of Death Registry.

During a median follow-up of 21 years (1,345,882 person-years), 507 men (1.4%) and 319 women (0.8%) initiated renal replacement therapy (n = 157) or died of CKD (n = 669).

The risk associated with body weight started to increase from a BMI of 25.0, but this increased risk was not seen in participants with BP less than 120/80 mm Hg.

In contrast, in participants with even moderately increased BP (pre-hypertension or hypertension), there was a progressive increase in the risk for kidney disease with increasing BMI suggesting an almost 6-fold increased risk in participants with a BMI greater than 35.

The study strongly suggests that individuals with a BMI greater than 30 are increasingly vulnerable to kidney disease even with a modest increase in blood pressure.

This finding has several important clinical implications:

1) Blood pressure should be carefully monitored in all individuals with BMI greater than 30.

2) Even moderately elevated blood pressure (pre-hypertension) should be addressed with lifestyle and, if necessary, pharmacological treatment in obese individuals.

3) Blood pressure treatment targets in obese patients may need to be similar to targets in patients with diabetes (i.e. below 130/80 mm Hg).

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