Neuropsychological functioning of insomnia patients and normally sleeping persons

Diagnostic criteria for insomnia, as well as patient complaints, imply that insomnia patients demonstrate cognitive difficulties. However, current research presents considerable inconsistencies regarding this matter. This study aimed to identify the neurocognitive profile of insomnia by potentially uncovering neuropsychological deficits in subjective insomnia. Thirty-six insomnia patients (15 males, 21 females) were very closely matched for gender, age, years of education, and ethnicity to a control group of 36 (14 males, 22 females) normally sleeping community contacts. Participant age ranged from 18 to 67, with the average age being close to 50 years old. The present study made use of formal diagnostic criteria, the Research Diagnostic Criteria for Insomnia Disorder by the American Academy of Sleep Medicine. All participants completed a valid, reliable and standardized insomnia questionnaire, the Insomnia Severity Index. They also completed a neuropsychological testing battery, which included measures of executive functioning, working memory, processing speed, attention, and reaction time. Results of this study point toward a mild executive functioning and working memory deficit in insomnia. Results also indicated enhanced performance on simple tasks of visual scanning and motor speed for the insomnia group, which can be potentially linked to the physiological hyperarousal characteristic of insomnia patients. As hypothesized, the control group did not perform significantly better than the insomnia group on measures of attention, verbal fluency, and reaction time. This hyperarousal characteristic of insomnia can be interpreted within the framework of compensatory effort ; in some tasks it may help compensate for deficits, resulting in normal performance. However, tasks of increased mental load , such as the working memory and some executive functioning tasks used in the present study may be more suitable for revealing cognitive difficulties in insomnia