The study demonstrated increased thalamic DAT (dopamine transporter) uptake in people with EDS , which further correlates with the severity of EDS, suggesting that increased dopaminergic function may be associated with EDS in humans. By using non-invasive SPECT molecular imaging , found no other changes related to DAT in DAT-rich areas such as the striatum, substantia nigra or globus pallidus.

The lead author Ms. Tayyabah Yousaf said, "The most important finding of our study is that increased thalamic DAT uptake is associated with the presence and severity of EDS in the general population, suggesting that it may be implicated in the underlying underlying daytime sleepiness. " The study findings were published in Sleep Medicine .

Yousaf and colleagues investigated whether thalamic dopaminergic function would be altered in people with EDS by assessing DAT with (123I) FP-CIT single photon emission CT ( SPECT ). For their case-control study, the first identified people over age 30 who were registered as healthy subjects in the Parkinson's Progression Markers Initiative ( PPMI ) database.

None had significant neurological dysfunction or first-degree family members with Parkinson's disease. All had a Montreal Cognitive Assessment ( MoCA ) score over 26 and a Geriatric Depression Scale (GDS) score under 5. Using the Epworth Sleepiness Scale, the authors set a score of 10 or higher as a cutoff for EDS.

Each of 21 people who made the EDS cutoff was matched with a healthy control without EDS, using age, gender, years of education, and rapid-eye-movement sleep behavior disorder questionnaire scores. No EDS participants or controls had dementia, depression, or other neurological or psychiatric conditions.

Depressive features and anxiety were assessed by the short version of the GDS and State Trait Anxiety Index total score. Global cognitive status was measured using MoCA. The authors found no significant differences in neuropsychiatric, autonomic, or cognitive assessments between the EDS and control groups.

The mean thalamic (123I) FP-CIT specific binding ratio (SBR) was significantly higher in participants with EDS than in those without EDS (1.78 vs. 1.64). In linear regression analyses, increased thalamic SBRs correlated significantly with worse EDS scores, even after adjustment for age and gender in people with EDS. No other associations were found between clinical / imaging data and EDS on univariate analysis.

"Considering the significant negative impact EDS has on daily activities, general health and quality of life, it is important that we try to unravel the pathophysiology of daytime sleepiness in order to understand how best to treat it in the general population," Ms. Yousaf advised.

"Given the complexity of sleep and the small sample size of our cohort, these findings can not definitively declare that thalamic dopaminergic function solely EDS, but we can postulate that it is likely to contribute, alongside non-dopaminergic systems, to the pathophysiology of EDS , "he noted.

"Gaining a deeper understanding of the neurophysiological alterations associated with daytime sleepiness will equip clinicians with tools to tailor treatment on a patient-specific basis, with reduced side effects and maximum benefit for the patient," Ms. Yousaf said.