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
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
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.