March 24, 2003

Daytime sleepiness trouble for dialysis patients

By Tia Webster

Clinicians long have noted that hemodialysis patients sleep during treatment, a phenomenon that often has been attributed to fatigue. But during her clinical work as a nurse practitioner, Emory researcher Kathy Parker began to suspect this problem might really be excessive daytime sleepiness—the inability to maintain an alert, awake state.

Parker conducted a study designed to establish the presence or absence of daytime sleepiness in these patients and to identify associated demographic, metabolic and sleep-related correlates. Her results were published in the February issue of the American Journal of Kidney Diseases.

Parker and her Emory colleagues studied a sample of 46 otherwise healthy hemodialysis patients on a nondialysis day so they could assess the prevalence and severity of daytime sleepiness independent of the effects of treatment. Sub-jects underwent a laboratory-based polysomnogram to measure nocturnal sleep.

Using conventional criteria, the researchers manually scored the sleep stages, apneas and hypopneas, periodic leg movements, and brief arousals. Sleep variables were calculated and included total sleep time, sleep efficiency and percentage of total sleep time spent in the stages of non-rapid eye movement (REM) sleep and REM sleep.

The next day, subjects took a Multiple Sleep Latency Test (MSLT), a laboratory-based daytime nap study that measures how quickly an individual falls asleep in a dark, quiet room (physiologic sleepiness). Subjective sleepiness, an assessment of an individual’s chance of dozing during the day, was measured via the Epworth Sleepiness Scale.

One-third of the subjects had MSLT scores that suggested abnormal levels of physiological daytime sleepiness, and 13 percent had scores consistent with severe, pathological sleepiness. More than 30 percent exhibited significant subjective daytime sleepiness. Subjects with greater physiologic sleepiness had greater numbers of apneas and brief arousals in their sleep at night. No correlation between physiological and subjective sleepiness was found, suggesting that hemodialysis patients may physiologically be very sleepy but have little insight into the severity of the problem.

“The results indicate that daytime sleepiness is common in hemodialysis patients and may be severe despite the absence of obvious clinical risk factors for the condition,” Parker and her colleagues wrote. “Thus, research designed to identify cost-effective indicators of daytime sleepiness and evaluate the detrimental effects of sleepiness on clinical outcomes in hemodialysis patients is warranted.”

The study was funded by the National Institute of Nursing Research. Parker’s research team included colleagues from the Department of Neurology (Sleep Disorders Center) and the Renal Division.