Test of early warning signs and RT-QuIC in patients with idiopathic olfactory dysfunction

Background. The number of persons living with dementia is increasing in Denmark and worldwide because the population is generally growing older. Dementia with Lewy bodies (DLB) is the second most prevalent etiology among the neurodegenerative diseases that give rise to dementia.

DLB is characterized by many prodromal symptoms years before dementia is evident. Currently, little is known about the course of symptoms in the prodromal phase, and furthermore, the diagnosis of DLB can be clinically challenging, especially in the early stages. DLB is like Parkinson's disease (PD), characterized by the accumulation of alpha-synuclein, which misfolds and aggregates within neurons in so-called Lewy Bodies; this assumably drives the neurodegeneration. A novel technique for the measurement of misfolded alpha-synuclein is Real-Time Quaking-Induced Conversion (RT-QuIC), which may be able to support the diagnostic process as well as aid in identifying patients with prodromal DLB. This would enable earlier symptomatic relief and care and potentially promote the search for disease-modifying therapies, which is currently absent.

Objectives. The overarching objective of this project is to identify early clinical warning signs and biomarkers in prodromal DLB.

Method. Study 1: Exploratory cross-sectional case-control study of patients with olfactory dysfunction versus individuals without olfactory dysfunction assessing pathological alpha-synuclein by RT-QuIC and prodromal symptoms of DLB and Parkinson's Disease.

Study 2: Longitudinal follow-up in Danish registries on diagnosing PD and dementia.

Inclusion criteria with patients iOD:

• Age 55 -75 years of age
• Slowly progressing and non-fluctuating iOD
• Able to give informed consent and to cooperate as evaluated by the PI

Exclusion criteria with patients iOD:

• Diagnosed with a neurodegenerative disease or major neurological/psychiatric condition.
• Anosmia/hyposmia caused by sino-nasal disease (including chronic rhinitis and allergy), after trauma, infection, congenial, olfactory dysfunction due to surgery, or toxins/drugs affecting the olfactory function.
• Olfactory dysfunction with response to systemic or local corticosteroids if tried
• Severe nasal cavity abnormalities or infections.
• Overt signs of dementia or PD
• Current alcohol or drug abuse
• Terminal illness
• Diagnosed with neurodegenerative disease or major neurological/psychiatric condition.

Inclusion criteria controls:

• Age 55 -75 years of age
• Able to give informed consent
• Able to cooperate as evaluated by the PI

Exclusion criteria controls:

• Olfactory dysfunction on clinical test
• Overt signs of dementia or PD
• Severe nasal cavity abnormalities or infections.
• Current alcohol or drug abuse
• Diagnosed with neurodegenerative disease or major neurological/psychiatric condition.

Fifty patients with idiopathic olfactory dysfunction (iOD) will be recruited from an anosmia clinic and community with posters in relevant newspapers and clinics. Also, 50 controls will be recruited from the community with posters in relevant newspapers and clinics.