Olfactory Impairment Can Precede Development of Parkinson's Disease

During the course of follow-up, 35 men developed the disease. The study was performed at Kuakini Medical Center (Honolulu, Hawaii, USA).

Decreased odor identification was associated with older age, smoking, more coffee consumption, less frequent bowel movements, lower cognitive function, and excessive daytime sleepiness, but even after adjusting for these factors, those with the lowest olfactory scores, meaning they had the poorest odor identification, had a five times greater risk of developing PD than those with the highest scores.

The pathology of smell impairment in PD is not completely understood, but nerve loss and the formation of Lewy bodies, abnormal clumps of proteins inside nerves cells that are thought to be a marker of PD, are known to take place in the olfactory structures of patients with the disease. A study involving brain dissection of deceased patients with neurologic disease found that olfactory structures are the earliest brain regions affected by Lewy degeneration, which supports the idea that an impaired sense of smell could be one of the earliest signs of the disease.

The study was published in the March 21, 2008, Annals of Neurology, the official journal of the American Neurological Association.


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