Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2024 Oct 15;14(7):1877718X241298708.
doi: 10.1177/1877718X241298708. Epub 2024 Nov 1.

Decline of olfactory function in Parkinson's disease: A ten-year longitudinal study

Dareia S Roos  1   2 , Martin Klein  3 , Richard L Doty  4 , Henk W Berendse  1   2
Affiliations
Free article

Decline of olfactory function in Parkinson's disease: A ten-year longitudinal study

Dareia S Roos et al. J Parkinsons Dis. .
Free article

Erratum in

Abstract

BackgroundOlfactory dysfunction is a prodromal sign of Parkinson's disease (PD) present in up to 90% of patients. However, it is unclear whether or not olfactory function worsens over the course of the disease.ObjectiveIn this study we examined whether the rate of decline of olfactory function in PD patients exceeds the expected age-related decline.MethodsOlfactory function was tested in 90 PD patients at baseline (age at baseline 58.3 years, 68.9% males) and an average 10 years later using the 40-item University of Pennsylvania Smell Identification Test (UPSIT). To screen for concomitant cognitive deficits as a potential confounder, the Mini-Mental State Examination (MMSE) was used.ResultsAt baseline, the mean UPSIT score was 22 points. Over the average 10-year follow-up period olfactory function decreased in 81.1% of PD patients, even in the youngest patients in whom no age-related decline was expected. The mean decrease was six UPSIT points (p < 0.001), which exceeds the expected age-related decline derived from a previous study. When excluding patients with an MMSE score below 24, reflecting cognitive deficits that might interfere with olfactory test performance, UPSIT score still decreased by almost 7 points over the follow-up period.ConclusionsOlfactory function in PD declines more rapidly with increasing disease duration than can be explained by aging or cognitive decline alone. As such, olfactory function appears to be a clinical marker of disease progression in PD that can be measured non-invasively and deserves consideration as part of multimodal phenotyping to monitor disease progression.

Keywords: Parkinson disease; cognition; disease progression; smell.

Plain language summary

Up to nine out of ten patients with Parkinson's disease (PD) experience olfactory loss. We wanted to find out if this loss further declines with disease progression. We tested the sense of smell in 90 PD patients at the start of study and again about ten years later using the University of Pennsylvania Smell Identification Test (UPSIT). Patients were around 58 years old at study entry and most were men. We also tested their cognitive functioning to make sure it did not affect the smell test results. We found that the sense of smell got worse in eight out of ten PD patients over the ten years of follow-up. Also this was found in younger patients who wouldn’t normally lose that much of their sense of smell due to aging. On average, the smell test scores dropped by six points (out of a total of 40 points), which is more than expected in normal aging. Even after excluding patients with cognitive problems, the drop in UPSIT score was still about seven points. This shows that the sense of smell worsens faster in people with PD than would be expected from aging or cognitive decline alone. Therefore, testing olfactory function could be a useful way to monitor the progression of PD in a non-invasive way.

PubMed Disclaimer

Conflict of interest statement

Declaration of conflicting interestsRL Doty is President of, and major shareholder in, Sensonics International, the manufacturer and distributor of smell and taste tests, including the test employed in this study.

References

Publication types

LinkOut - more resources