Obesity, High Blood Pressure Linked to Type of Kidney Cancer
What Chow and colleagues found was that men with the highest body mass had nearly double the risk for developing kidney cancer, compared with men who had the lowest body mass. There also was a direct association between higher blood pressures and higher risk of kidney cancer, she reports.
In addition, six years after the beginning of the study, subjects were checked for weight and blood pressure, a strategy that led the researchers to a crucial discovery: Regardless of the original measure of blood pressure or body mass, increases in either measure contributed to a risk for later disease.
What the study does not demonstrate conclusively are the reasons for why high blood pressure and obesity lead to renal cell cancer. But Chow and colleagues suggest some hypotheses about what those mechanisms may be: Obese persons have high concentrations in the blood of an agent known as insulin-like growth factor I, which is believed to affect the growth of cells. As for high blood pressure, changes in kidney function that accompany high blood pressure may render the organ susceptible to carcinogens and tumor growth, they suggest.
David L. Katz, MD, MPH, associate professor of medicine at Yale University School of Medicine, says the report "provides compelling evidence linking obesity and hypertension to renal cell cancer."
Katz, who reviewed the report for WebMD, says the strength of the study is the large number of patients who were followed. "What is most impressive is the volume of data collected and the extensive follow-up," Katz tells WebMD. "One hopes in epidemiology that if you look at enough people for long enough time, the patterns that emerge approximate the truth."
Katz says a possible shortcoming in the report is the fact that the men in the study were construction workers; it is not clear whether the incidence of cancer among that group was markedly different than the general population, or whether the incidence of cancer in the group was related to occupational exposures, he says.
But he says that obesity has been implicated in a host of conditions. Though there is a "worsening epidemic" of obesity in the U.S., there is as yet no clearly defined strategy for intervening and treating the problem, he says.