By Linda Carroll, NBC News
Couch potatoes may have an increased risk of chronic kidney disease, even if they take time out from sitting to exercise vigorously, a new study suggests.
British researchers found that people who spent the least amount of time sitting were also the least likely to have chronic kidney disease. And that was especially true for women who spent less than three hours a day seated, according to the study published in the American Journal of Kidney Disease.
It's not clear how sedentary behavior could lead to kidney disease, said study co-author Thomas Yates, a researcher at the University of Leicester and the University Hospitals of Leicester NHS Trust.
But, sitting has also been linked to other chronic diseases, such as type II diabetes, Yates said.
"Sitting jobs need to be broken up with periods of standing," Yates said. "As these findings start trickling down to the public consciousness, it is hoped it will affect occupational health considerations."
Yates and his colleagues surveyed 5,650 Britons, asking about lifestyle factors such as smoking, exercise and sitting time. They also examined the study volunteers for signs of kidney disease. The researchers found a link between hours spent sitting and kidney disease, even after they took into account factors such as smoking, age, gender, ethnicity, body-mass index, blood pressure, medications and hours spent exercising.
The researchers divided the volunteers into three groups: people who sat 8 to 24 hours a day were categorized as "high," those who sat 3.2 to 7.8 hours a day were considered "moderate," and those who sat 0 to 3 hours a day were categorized as "low."
Women with low amounts of sitting time had a 30 percent reduction in risk of kidney disease compared to those in the high category. Men who spent little time sitting got a 20 percent reduction in risk compared to those who sat the most.
Exercise seemed to reduce, but not eliminate, the heightened risk in men who were couch potatoes. Exercise did not appear to ameliorate the effects of sitting in women, though.
Does that mean we should all give up our office jobs and find something that requires more activity?
No, said kidney expert Dr. Jeffrey S. Berns, a professor of medicine at the University of Pennsylvania School of Medicine.
The researchers found an association between long hours sitting and a greater likelihood of having kidney disease, Berns explained. That doesn't prove that sitting actually caused the kidneys to become diseased.
"Someone who sits around and doesn't have risk factors for kidney disease shouldn't worry," Berns said. "While it's certainly plausible to think that sitting may contribute to diabetes, obesity, and high blood pressure, it's much harder to come up with a way that inactivity could be a direct cause of kidney disease. The flip side of this is that people with chronic kidney disease are known to be less active. And my suspicion is that these results are confounded by that."