Circulating Ghrelin as a Biomarker for Dementia (GDEM3)

The primary objective of this study will explore whether circulating acyl-ghrelin (AG) and unacylated-ghrelin (UAG) are reduced in neurodegenerative disease associated with cognitive impairment. It will focus on validating pilot data generated following the analysis of Parkinson's disease (PD), Parkinson's disease dementia (PDD) and healthy cohorts (IRAS project ID: 250933). In addition to the advantages of study replication we will extend the analysis to include two further patient groups that are associated with cognitive impairments, namely, Alzheimer's dementia (AD) and dementia with Lewy bodies (DLB). This study will increase confidence in the replication of our findings. This will be a cross-sectional study using peripheral venous blood.

Participants will undergo venous blood collection following an overnight fast and 5, 60 and 180 minutes following food intake.

Inclusion Criteria: Age > 60 years Subject or carer / legal representative is willing to sign consent document Specific criteria for each group; Parkinson's Disease PD diagnosed by a movement disorder specialist and meets the diagnosis of PD MoCA > 26/30 No evidence of cognitive symptoms causing functional impairment Parkinson's Disease Dementia PD diagnosed by a movement disorder specialist Duration of motor symptoms > 1 year Meets MDS task force criteria for PDD MoCA < 21/30 Dementia with Lewy Bodies Meets criteria for probable DLB as defined by the 4th report of the DLB consortium Alzheimer's Disease Meets criteria for probable AD dementia (consistent with NIA/AA core clinical criteria for probable AD dementia) Exclusion Criteria: Age < 60 years Current major depression Use of anti-psychotic medication Type I or Type II diabetes mellitus (DM) (excluding diet-controlled DM) Tobacco use BMI <15.0 kg/m2 BMI > 30 kg/m2 Comorbid gastrointestinal disease i.e. includes Coeliac, active Inflammatory Bowel Disease (Colitis), evidence for active gastric ulcers within the last 12 months, but excludes gastroesophageal reflux and hiatus hernia. >5 kg weight change over the preceding 3 months (determined by researcher from previous clinic visit and discussion with partner/carer) Significant active comorbidity Difficult venous access Vagotomy Additional disease specific exclusions; Parkinson's Disease exclusion criteria Evidence of dementia or mild cognitive impairment Deep brain stimulation (DBS) Use of Duodopa Parkinson's Disease Dementia exclusion criteria Dementia within 12 months of diagnosis of PD DBS Dementia with Lewy bodies exclusion criteria Onset of motor Parkinsonism symptoms greater than 12 months prior to dementia diagnosis Alzheimer's dementia exclusion criteria Presence of PD, PDD, DLB, or Frontotemporal Dementia (FTD) Controls exclusion criteria Evidence of parkinsonism Evidence of dementia or mild cognitive impairment MoCA <26/30