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Patients with kidney disease who need dialysis do markedly better if they undergo the procedure overnight, while they sleep, than they do with the traditional method that requires them to go regularly to a hospital clinic for treatment, a new Canadian study shows.

"Being in the home improves quality of life," Bruce Culleton, a nephrologist and co-author of the study, said in an interview.

"It also results in some positive medical outcomes like improved heart function, lower blood pressure and a reduced need for medication."

The research, published in today's edition of the Journal of the American Medical Association, shows that nocturnal hemodialysis reduced left ventricular mass (a swelling of the heart that is a leading cause of heart failure) by an average of 13.8 grams during the six-month study period.

By contrast, patients undergoing traditional hemodialysis saw their LV mass increase, on average, by 1.5 grams during the same time frame.

"From a medical perspective, this 15-gram reduction in LV mass is quite significant," said Dr. Culleton, who formerly practised at Foothills Medical Centre in Calgary and is now medical director of the renal division of Baxter Healthcare Corp. in Deerfield, Ill.

A heavier heart is often an indication that it is not pumping properly.

But patients, he said, are more likely to notice that they no longer require blood pressure medication, and that their quality of life is improved.

The 52 patients who participated in the study were randomly assigned to either conventional or nocturnal hemodialysis.

Dialysis is a procedure used to treat kidney failure. Blood is removed from the body and cleansed of toxic material that would normally be cleaned out by the kidneys.

In traditional hemodialysis, patients undergo the procedure at a clinic three times weekly for periods of about four hours at a time. With nocturnal hemodialysis, they are hooked up to a machine six nights a week, for about seven hours at a stretch, while they sleep.

"Because you get your treatment at night in your home, you have your days to yourself, you have your freedom," said Catherine O'Meara of Calgary, who participated in the study.

Nocturnal dialysis also allows her to work as a cardiovascular nurse and to take part in hobbies such as golfing and camping. (When she camps, she takes a couple of nights off dialysis.)

Ms. O'Meara said even though she is a nurse, learning how to set up the equipment was a bit daunting at first. But she encourages kidney-failure patients to choose the overnight option.

"If you can learn a cake recipe - just follow all the steps - then you can do this," she said.

Dr. Culleton said nocturnal dialysis is not for everyone; it is appropriate for about 10 to 20 per cent of kidney-failure patients, in particular those who are independent and not daunted by the technology or fearful of needles.

He said the reason for the better outcomes is not entirely clear, but researchers have some theories.

Conventional hemodialysis patients receive 12 hours of treatment weekly, while nocturnal hemodialysis patients get a minimum of 36 hours.

The additional time does not appear to be the key factor - rather, it is the pace of treatment.

In conventional hemodialysis, blood is pumped in and out of the body quickly, which can wreak havoc on blood pressure and the heart. In nocturnal dialysis, blood is pumped and cleansed more slowly.

Braden Manns, an associate professor of medicine and community health sciences at the University of Calgary and co-author of the study, said the improvements in the health of patients undergoing nocturnal dialysis were remarkable, and it should be offered as a treatment option.

"The boost to people's quality of life was similar in magnitude to having a kidney transplant," he said.

Ms. O'Meara said that's true, at least in the short-term, but she is still anxiously awaiting her kidney transplant. (She has been on a waiting list for 2½years.) "Nocturnal hemodialysis allows me to survive; it doesn't quite allow me to live," she said.

"I still want a transplant."