Smell loss (anosmia) is a common finding in people with PD, although it is also quite common in older age (Ross 2008). Population studies assessing the prodromal phase of PD have therefore included individuals with smell loss. However, the differential diagnosis of anosmia is broad, and it is likely that only a subset are linked to neurodegeneration. Some evidence suggests that people with the anosmic prodrome have a different phenotype to other forms of prodromal PD (Rees 2019).

Methods We assessed neurologically healthy patients aged 60–80y from two specialist ENT clinics (James Paget Hospital, Norfolk; RNTNE, London). All participants had a diagnosis of idiopathic anosmia after comprehensive investigation. Participants completed online PREDICT-PD testing (www.predictpd.com) followed by an in-person assessment with standardised physical, cognitive and autonomic tests.

Results We recruited 28 participants (17 women) mean age 69.9y (SD 4.9y). Participants had a mean of 14.4 years of education (SD 3.1). Adjusted MoCA scores had a mean of 25.9/30 (SD 2.6). There was a range of subtle motor impairment, median MDS-UPDRS III 4.5 (IQR 1.0- 8.0, max 20) and median 3m up-&-go time 8.5s (IQR 7.8–9.6). Those with the highest risk had higher tremor scores in the MDS-UPDRS

Conclusions There is a correlation between risk of PD and cognition. There is no significant gross motor or autonomic dysfunction in these patients, but the highest risk participants had higher tremor subscores. Further recruitment will allow clear delineation of the anosmic prodrome of PD.