TUESDAY, Dec. 4, 2001 (HealthDayNews) -- Older people undergoing dialysis -- artificial treatment for kidney failure -- lived longer if they had their sessions in the morning rather than the afternoon, finds a new study of patients in Georgia.
The study of 242 kidney-failure patients, aged 60 and older, found that morning-session patients survived an average of 941 days, compared with 470 days for afternoon-shift patients, reports the Dec. 5 issue of the Journal of the American Medical Association.
Kathy P. Parker, the professor of nursing at Emory University, in Atlanta, who initiated the study, says the difference might be due to the way the body reacts to medical treatment at different times of the day.
Kidneys fail when the organs cannot concentrate urine and rid the body of wastes. Dialysis machines do the jobs for them. About 300,000 Americans are treated for this ailment each year. In the study, the morning shift ran from 6 a.m. to 11 a.m., while the afternoon shift was from 11:30 a.m. to 4 p.m.
"Treatment may interact with sleeping and waking cycles. Certain times are particularly bad in terms of sleep," says Parker.
For instance, she says the effectiveness of chemotherapy for certain kinds of cancer varies with the time of day that the drugs are administered. "This study raises an interesting question of the interaction of medical treatment with the circadian [sleep and wake] system," Parker says.
But Dr. Leslie Spry, medical director of the Dialysis Center of Lincoln, in Nebraska, and a member of the public education committee of the National Kidney Foundation, has a more prosaic set of explanations.
To start with, Spry says, "My guess is that it has to do with desirability. The morning shift is the most desirable because everybody likes to come in, get the dialysis done and go home. The next most desirable is the evening shift, because people work. Nobody likes the afternoon shift. You get the most desirable patients on the other two shifts."
And Spry says there are major differences in two important characteristics, body mass index (BMI) and ethnicity, among morning and afternoon patients in the Georgia study. Black people are known to do better on dialysis than whites, and the same is true of persons with a high BMI, a measure of obesity.
In the Georgia study, 65.3 percent of the morning-shift patients were black, compared with 41.3 percent of those on the afternoon shift. And the average BMI on the morning shift was much higher than on the afternoon shift.
"I would say that the time-of-day-survival-benefit statistics they cite in this particular study could be explained by the black population and BMI," Spry says.
More studies are needed about the possible time-of-day effect, Parker says. For example, it's not clear whether such an effect would apply to younger patients, because sleep patterns change with age, she says. "Older people are more phase-advanced -- they go to bed earlier and get up earlier. It may not be that one size fits all. In younger patients it may be different."
Ultimately, the report says, "Randomized trials may be required to determine definitively whether morning shift is protective for any age group."
What To Do
"We certainly are not advocating that everyone should be dialyzed in the morning," Parker says. And Spry says patients will continue to seek morning or evening dialysis sessions on the grounds of convenience alone.
For information about kidney disease and dialysis, consult the National Kidney Foundation or The Nephron Information Center.
