Impaired sense of smell may be early indicator of Parkinson...( Impaired sense of smell occurs in th...),Health

Impaired sense of smell occurs in the earliest stages of Parkinsons disease (PD) and there is mounting evidence that it may precede motor symptoms by several years, although no large-scale studies had confirmed this. In the first study involving the general population, researchers found that smell impairment can precede the development of PD in men by at least four years. The study is published in the Annals of Neurology (http://www.interscience.wiley.com/journal/ana), the official journal of the American Neurological Association.

Led by G. Webster Ross of the VA Pacific Islands Health Care System and the Pacific Health Research Institute in Honolulu, Hawaii, the study included 2,267 men from the Honolulu-Asia Aging Study who received olfactory testing at least once, either between 1991 and 1993 or between 1994 and 1996, and were followed for up to eight years to find out if they developed PD. During the course of follow-up, 35 men developed the disease.

The results showed that an odor identification deficit can predate the development of PD by at least four years, although it was not a strong predictor beyond this time period. 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.

One interpretation of this finding is that the relationship of olfactory deficits to higher risk of future PD begins to weaken beyond a threshold of approximately four years between testing and diagnosis, the authors state. The fact that the time from olfactory testing to diagnosis was shortest among those with the lowest olfactory scores supports this. In
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