Another Danger for Smokers: Kidney Disease

Oct. 16, 2000 -- Doctors have known for a while now that smoking may increase the risk of kidney disease in people with diabetes. Now, a study shows that smoking may lead to potentially dangerous changes in kidney function even in otherwise healthy people.

For the study, which appears in the Annals of Internal Medicine, a group of researchers from the Netherlands studied urine and blood samples from more than 7,000 people ages 28 to 75. The participants were divided into three groups: nonsmokers, current smokers, and former smokers (defined as those who had not smoked for more than a year).

Compared with nonsmokers, the current and former smokers had higher levels in their urine of a substance called albumin, and their bodies were slower to excrete another substance called creatinine. Higher albumin in urine and delayed creatinine excretion are early signs of abnormal kidney function, but since these conditions don't usually cause symptoms, most people don't know they may be starting to have kidney problems.

Other studies have shown that people with diabetes have similar changes in their kidney function if they smoke, but the study authors say their research is the first to demonstrate that smoking can have bad effects on your kidneys even if you have no other diseases. They suggest that certain toxic substances in tobacco smoke may be to blame.

The study was conducted by Sara-Joan Pinto-Sietsma, MD, and colleagues from University Hospital Groningen and Groningen University Institute for Drug Exploration in Groningen, Netherlands. The researchers point out that while they found a link between smoking and changes in kidney function, none of the study participants actually developed kidney disease. So the results must be confirmed in larger studies, in which people are followed for longer periods of time, to see if the changes seen in blood and urine tests amount to anything.

The one bit of good news is that former smokers had fewer kidney abnormalities than current smokers, suggesting that smoking-induced changes are temporary and may be reversed if a person stops smoking.

A member of the National Kidney Foundation's public education committee tells WebMD that studies in diabetics show that it takes about a year from the time someone stops smoking until their level of albumin drops to normal. If it continues to rise, a serious situation called microalbuminuria will develop.

"We now know that microalbuminuria is the earliest manifestation of diabetic injury to the kidney that we can find," says Les Spry, MD. "And we know that that will forecast ultimate destruction of the kidney." If that happens, dialysis and/or a kidney transplant will be needed.

In people with diabetes who are found to have microalbuminuria, it usually takes five to 10 years before serious kidney disease develops, Spry says. Taking a "leap of faith," he theorizes that it should take longer for nondiabetics who develop microalbuminuria to become seriously ill with kidney disease.

The study, he says, is yet another warning to smokers that continuing their habit is hazardous to their health.