IH and Cognition: The Scope of the Problem
In the Real-World Idiopathic Hypersomnia Outcomes Study (ARISE), 63% of participants reported moderate to severe cognitive complaints.1 Severe cognitive complaints were reported by 35.1% and 18.4% of participants with and without long sleep time (LST), respectively. These results are consistent with several prior studies indicating that over 1/2 of the patients with IH experience cognitive dysfunction.
Memory and Attention Concerns
Generally, cognitive difficulties include such areas as memory problems, forgetfulness, attention deficit, mind going blank, and inability to remember the beginning of an activity—all of which have been demonstrated in patients with IH at higher rates than controls.2 In a study using a 30-minute sustained attention task (Perception and Attention Functions test battery–Vigilance; WAFV), people with IH showed longer response times and more response omissions compared with subjects without IH, especially during the second half of the test.3 This result demonstrates a lower ability to maintain attention over time in the absence of a stimulating environment.
Brain Fog
Brain fog can be defined as an inability to think clearly or concentrate at any time throughout the day. In the real-world Hypersomnia Foundation registry study, brain fog was reported by roughly 80% of participants—the most common symptom after excessive daytime sleepiness.4 Interestingly, brain fog was also reported by 54% of participants currently receiving treatment, reinforcing the need for more comprehensive treatment and more effective therapies for these patients. While brain fog is a significant cognitive complaint of people with IH, it is often an underutilized criterion for diagnosis. Indeed, despite its prominence in patients with IH, it is not included as a feature of IH in the ICSD-3, which can hinder recognition of the disorder.
Depression
In the ARISE study, over 1/3 of patients with IH reported moderately severe to severe levels of depressive symptoms.1 Another study from the Cleveland Clinic reported even higher levels: 58% scored their depressive symptoms as moderate to severe.5Â Other studies have corroborated these data, underscoring the problem of depression and other psychiatric comorbidities (eg, anxiety) in patients with IH.
Notably, patients with IH also report high levels of absenteeism, presenteeism, and overall activity impairment due to idiopathic hypersomnia. However, this is not surprising given that the more common symptoms of IH—excessive daytime sleepiness, cognitive difficulties, brain fog, depression—could all interfere heavily with work responsibilities.
