Daytime sleepiness in stable hemodialysis patients

Background. Patients frequently sleep during hemodialysis (HD), a behavior often attributed to treatment-related fatigue and/or simple boredom. The possibility that this behavior reflects a more pervasive underlying increase in daytime sleepiness has never been systematically examined. Thus, we studied a sample of HD patients on an off-dialysis day to establish the presence or absence of daytime sleepiness independent of effects of treatment, quantify its severity, and identify associated demographic, metabolic, and sleep-related variables. Methods: Forty-six stable HD patients underwent polysomnography, followed the next day (a nondialysis day) by the Multiple Sleep Latency Test (MSLT; low score = greater sleepiness), a measure of physiological daytime sleepiness. Subjects also completed the Epworth Sleepiness Scale (ESS; high score = greater sleepiness), a measure of subjective daytime sleepiness. Results: One third (n = 15) of subjects had MSLT scores suggesting abnormal levels of physiological daytime sleepiness, and six subjects had scores consistent with severe, pathological sleepiness. Thirty percent (n = 14) had significant subjective daytime sleepiness as measured by the ESS. However, MSLT and ESS scores were unrelated. Higher indices of sleep apnea (r = -0.324; P = 0.028) and brief arousals (r = -0.370; P = 0.009) correlated significantly with increased physiological, but not subjective, sleepiness. Longer nocturnal sleep latencies (r = 0.350; P = 0.017) and greater percentage of rapid-eye-movement sleep (r = 0.302; P = 0.042) were associated with decreased physiological sleepiness. Other major demographic, metabolic, and sleep-related variables did not correlate with MSLT scores, and none of the variables examined were related to ESS scores. Conclusion: Daytime sleepiness is common in HD patients and may be severe despite the absence of obvious clinical risk factors for the condition. Thus, research designed to identify cost-effective indicators of daytime sleepiness and evaluate the detrimental effects of sleepiness on clinical outcomes in HD patients is warranted.