Hypertension Affects Kidneys Too, Not Just Heart

A new study finds that increases in blood pressure and body mass were associated with greater risks of kidney cancer in U.S. men and women.

Researchers from the University of Pittsburgh studied data from 2 large U.S. cohorts, evaluating kidney cancer incidence in 156,774 women participating in the Women’s Health Initiative (WHI) clinical trials and observational studies, as well as fatal kidney cancer in 353,340 men who were screened as part of the Multiple Risk Factor Intervention Trial (MRFIT). Participants were followed for 15 to 25 years.
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While further research is needed “to determine the pathophysiologic basis of relationships between both higher blood pressure and the risk of kidney cancer, and whether specific drug therapies for hypertension can reduce kidney cancer risk,” according to the authors, they note that obesity and hypertension may to some extent represent a shared causal mechanism in the development of kidney cancer.

Among patients in the WHI, kidney cancer rates were increased in all categories of systolic blood pressure at or above 140 mm Hg, compared with rates of 120 mm Hg or lower. According to the authors, findings were similar across body mass index (BMI) categories, although statistical significance was seen only above 30 kg/m².

Among men that participated in the MRFIT, 0.26 percent of patients died from cancer during follow-up, and the risk increased along with systolic blood pressure, even within the normotensive range, report the authors. The hazard ratio for kidney cancer death was 1.29 for those with a blood pressure of 120 to 129 mm Hg, and 1.87 for those with a pressure greater than 160 mm Hg, compared with those with a systolic pressure less than 120 mm Hg. Death from kidney cancer was also associated with smoking with an adjusted HR of 1.75. The effects of smoking and systolic blood pressure on risk of death from kidney cancer were additive.

“Obesity is associated with increased glomerular filtration rate and increased renal plasma flow, which may render the kidneys more susceptible to kidney damage and carcinogenesis. Furthermore, patients with hypertension and chronic renal hypoxia caused by the upregulation of hypoxia-inducible factors that may in turn play a role in oncogenesis,” the authors wrote.

"Both obesity and hypertension have also been associated with oxidative stress and lipid peroxidation, which is hypothesized to play a role in kidney cancer pathogenesis," they continued. "In addition, obesity could increase cancer risk through increased levels of insulin and insulin-like growth factor I."

—Mark McGraw

Reference

Sanfilippo K, McTigue K, et al. Hypertension and Obesity and the Risk of Kidney Cancer in 2 Large Cohorts of US Men and Women. Hypertension. 2014.