Strong feelings of being sleepy during daytime hours are much more common in amyotrophic lateral sclerosis (ALS) patients than the general public, and appear to be associated with poorer cognitive skills and greater behavioral problems, a study from China reports.
Its researchers suggested that their findings, if confirmed in larger studies, could merit listing excessive daytime sleepiness as a “severe complication of ALS.”
The study, “Excessive daytime sleepiness in Chinese patients with sporadic amyotrophic lateral sclerosis and its association with cognitive and behavioural impairments,” was published in the Journal of Neurology, Neurosurgery & Psychiatry.
ALS affects several brain regions, causing not only motor dysfunction, but also cognitive impairment, behavioral changes, and sleep disturbances. Evidence suggests that about half of ALS patients have difficulties with cognitive and/or behavior.
Excessive daytime sleepiness (EDS) is estimated to affect between 2.5 and 9.0 percent of adults worldwide. It is characterized by persistent sleepiness and feeling of overwhelming fatigue in daytime hours, even with apparently adequate nighttime sleep.
EDS often interferes with work, school, and relationships, and can impair quality of life and cognitive function. While its underlying mechanisms are unclear, EDS has been associated with such psychiatric and neurodegenerative disorders as Alzheimer’s and Parkinson’s disease. But it has not been studied widely in ALS.
Researchers in Beijing decide to assess EDS frequency and its potential association with cognitive or behavioral problems in ALS. They recruited 121 patients and 121 age- and sex-matched healthy individuals, and assessed EDS using the Epworth Sleepiness Scale (ESS), a self-administered questionnaire that measures daytime sleepiness.
Patients (71 men and 50 women) had a mean age of 53, and disease severity was evaluated through the revised ALS Functional Rating Scale (ALSFRS-R).
Evidence of other sleep disorders was assessed through face-to-face interviews; cognition, behavior, depression, and anxiety were evaluated using validated tests.
Patients were found to have a significantly higher frequency of EDS (26.4%) than healthy individuals (8.3%), as well as significantly more severe EDS symptoms, suggesting an association between the two conditions.
Further analysis revealed ALS patients were at a four times increased risk of developing EDS, compared with healthy people.
EDS was diagnosed in 32 ALS patients, and they showed significantly worse overall ALS severity, including physical limitations like greater difficulties in moving in bed and adjusting bedclothes, compared to the 89 patients without an EDS diagnosis.
But ALS patients with EDS showed no significant differences in lung function to other patients, supporting evidence that suggests sleep disturbances are not dependent on lung health in ALS.
“The higher frequency of EDS symptoms in patients with ALS is not entirely due to nocturnal sleep quality and respiratory issues; rather, the neurodegenerative process itself seems to be involved,” the researchers wrote.
ALS patients with EDS also showed significantly worse cognitive abilities — particularly in memory — and behavioral changes than those without EDS, suggesting EDS may promote progression in these symptoms.
The researchers noted that larger studies are needed to confirm these associations, and — if confirmed — EDS could be “considered a severe complication of ALS,” as it appears to be linked to more severe overall dysfunction and a wider range of affected brain areas.
They also pointed out that EDS symptoms in ALS patients remain under-diagnosed and untreated. More timely diagnosis of EDS, as well as better treatment, might help to improve quality of life for these people.