03/01/2012 06:44 EST | Updated 05/01/2012 05:12 EDT

Kidney donors not at higher risk of heart disease, study suggests

TORONTO - Donating a kidney doesn't appear to put the people who do it at greater risk of developing heart disease, new Canadian research suggests.

It is known that people with reduced kidney function due to disease are more likely to develop cardiovascular conditions. So an international team of researchers, led by Dr. Amit Garg at the University of Western Ontario in London, set out to see if that risk carries through to healthy people who reduce their renal mass by donating a kidney.

The question has important health implications for the people stepping forward to give a loved one — or sometimes a stranger — a life-saving kidney. And it has important ethical implications for the medical teams assessing and advising would-be donors, the study suggests.

"We're very gratified that we don't see a signal," of cardiovascular disease, Garg, a kidney specialist at London Health Sciences Centre, said in an interview.

He said the fact that donors didn't seem to develop heart disease at greater rates than non-donors may suggest that reducing one's kidney mass in this way has a different effect on the body than if one loses kidney function as a result of damage done by a condition such as diabetes.

"Maybe it does speak to the fact that if you lose a kidney through a non-disease process ... and you're otherwise healthy, that may not have the same concerns as someone who loses half their kidney function from a disease," Garg said.

The study was published in the British journal BMJ. It is one of a series of studies that Garg and colleagues from across Canada and parts of the United States and Australia have undertaken to look at the health implications of donating a kidney.

In this work the group studied the medical records of 2,028 Ontario residents who were living kidney donors between 1992 and 2009, and compared them to 20,280 healthy non-donors from the province matched for age and gender.

In fact, for the non-donor group the researchers looked at only the healthiest people they could find, because they were likely to be most similar to the people approved as kidney donors. There is a stringent selection process in order to donate a kidney and typically only very healthy people are approved as donors.

Researchers found that in the first decade after donating a kidney, donors did not develop heart disease more frequently than healthy people who had not been donors. They followed people for a median period of 6.5 years, but in some cases the follow-up was as long as nearly 17.7 years.

The donors ranged in age from 34 to 50, with a median age of 43. Heart disease often doesn't manifest itself till later than this in the general population. Garg said decades of follow up will be needed to ensure that donors don't develop heart disease at higher rates when they hit the stage in life when it is more common.

But he said studies have shown that people who lose kidney function because of disease and who go on to develop heart disease do so within about eight years of the function loss. So if donating a kidney were to trigger heart disease, one might expect to see it in the near term, he suggested.

An editorial published in the same issue of the journal praised the paper, saying it makes an important contribution to the understanding of the long-term consequences of donating a kidney.

But authors Sarah White and Alan Leichtman of the University of Michigan warned that these results may not be true for all donors, noting that in recent years there has been a trend towards accepting living donors who are not the healthiest of the healthy, for instance a person with well controlled hypertension.

"Our study does not say one way or another whether that's an appropriate practice," Garg said. "Our study is saying that for the traditional types of donors we've seen, the results are very encouraging and reassuring that we aren't causing any undue harm in the donors, in supporting them in their wish to give the gift of life to a loved one."

White and Leichtman suggested additional studies should be done to see if the same results would be found in donors whose starting bill of health isn't as clean as the people typically approved for donation. Garg agreed, saying his group is looking at this question.