HONOLULU –– A team of local researchers found that loss of the sense of smell is linked to the development of Parkinson's disease in men. Moreover, the loss of this sense could precede the onset of Parkinson's by at least four years, a finding with potential clinical impact, according to a news release.

The findings were published in the February 2008 issue of Annals of Neurology, the official journal of the American Neurological Association. The research team is from the VA Pacific Islands Health Care System, Pacific Health Research Institute and the John A. Burns School of Medicine

"The connection between loss of smell and Parkinson's disease is not completely understood, but nerve loss is known to take place in the olfactory structures of patients with the disease. Although there is no known cure for Parkinson's disease, our findings offer an important early indicator for treatment before more advanced symptoms develop," said Dr. G. Webster Ross, lead author of the study.

The study group included 2,267 Japanese-American men from the Honolulu-Asia Aging Study, an outgrowth of the original Honolulu Heart Program based at Kuakini Medical Center that has made major contributions to research in cardiovascular disease, dementia, and Parkinson's disease over the past 40 years.

Research participants received olfactory testing at least once between 1991 and 1996, and were followed for up to eight years to find out if they developed Parkinson's disease. During the course of follow-up, 35 men developed the disease.

The results showed that an odor identification deficit could predate the development of Parkinson's disease by at least four years. Decreased odor identification was also associated with older age, smoking, more coffee consumption, lower cognitive function, excessive daytime sleepiness and other factors. Even after adjusting for these factors, those with the lowest olfactory scores had a five times greater risk of developing the disease than those with the highest scores.

The authors conclude: "Olfactory testing along with screening for other potential early indicators of Parkinson's could provide a simple and relatively economic means of identifying individuals at high risk for developing Parkinson's disease who could participate in trials of medications designed to prevent or slow disease progression." The study is located at Kuakini Medical Center in Honolulu.