Unawareness of Hyposmia in Elderly People With and Without Parkinson's Disease

Hyposmia is common in Parkinson's disease (PD) and is also observed with normal aging. It can be ascertained through objective testing, but it is unclear whether patients are aware of deficits and whether this has implications for cognitive status.

Subjects in the Arizona Study of Aging and Neurodegenerative Disorders were studied with annual motor and cognitive testing with objective smell testing (University of Pennsylvania Smell Identification Test; UPSIT) done every third year beginning in 2002. Those with a baseline UPSIT <25th percentile (hyposmia) were studied for presence of unawareness of hyposmia and cognitive status.

There were 75 subjects with PD and 143 nonparkinsonian controls with hyposmia. Lack of awareness of hyposmia was present in 16% of PD subjects and 47% of those without PD. In PD, there was no increase in unawareness in PD with dementia. In non-PD controls, unawareness was correlated with presence of dementia. Unawareness of hyposmia correlated most strongly with the neuropsychiatric tests of learning and memory. In controls without dementia or PD, 48% were unaware.

Querying patients about anosmia might be useful in parkinsonian disorders without objective testing. However, in elderly controls, it should be followed by objective testing and lack of awareness has implications for worsened cognitive status.