Isle team finds loss of smell is early signal of Parkinson’s
Isle researchers say the change precedes classic symptoms
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Hawaii researchers have discovered that the loss of smell is one of the first signs of Parkinson's disease, occurring before classic signs and symptoms.
"Our findings offer an important early indicator for treatment before more advanced symptoms develop," said Dr. G. Webster Ross, who led the research team from the Veterans Administration Pacific Islands Health Care System, Pacific Health Research Institute and John A. Burns School of Medicine.
The study was based on smell-testing of about 4,000 men from the Honolulu Heart Study.
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The loss of smell is one of the first signs of Parkinson's disease, occurring at least four years before classic signs and symptoms, Hawaii researchers have found.
"It's been known for 30 to 40 years now that smell is impaired in Parkinson's disease," Dr. G. Webster Ross said in an interview. What was not known until the Hawaii study is that impaired smell predates classic signs of rigidity, tremors and slowness of movement, he said.
"Our findings offer an important early indicator for treatment before more advanced symptoms develop," said Ross, who led a research team from the Veterans Administration Pacific Islands Health Care System, Pacific Health Research Institute and John A. Burns School of Medicine.
The study was based at Kuakini Hospital using data from the Honolulu Heart Study that began in 1965 with 8,006 Japanese-American men on Oahu born between 1900 and 1919. The research continued with a Honolulu-Asia Aging study in 1991.
Researchers studying the men over the years have increased understanding of heart disease and stroke, Alzheimer's and Parkinson's diseases, dementia and other diseases of the aging.
About 900 of the participants are still living, with the oldest about 104, Ross said. "They are delightful guys. Most are in their 90s, and many are still as sharp as can be. They're still very active, into all kinds of different projects."
Besides examining the men still living, they are doing as many autopsies as possible, he said. With clinical information available on the participants back to 1965, he pointed out, "It is extremely valuable to go back and correlate the findings during life with pathological lesions found after death."
The researchers hope to enroll children of the 1965 cohort in a new study which would provide valuable genetic information, Ross said.
Using a scratch-and-sniff smell identification test, researchers examined a little fewer than 4,000 men between 1991 and 1996, Ross said.
Twelve odors were on the cards, and participants had a choice of four odors to identify them after scratching and sniffing, he said. Men who did not have Parkinson's disease were followed by the researchers for up to eight years. In that time, 35 men developed the disease.
Older age, smoking, coffee consumption, lower cognitive function, excessive daytime sleepiness and other factors were associated with reduced smell, the researchers found.
But adjusting for those factors, Ross said, "Those with the worst olfactory function in 1991 had five times the risk of developing Parkinson's as those with the highest olfactory function."
The findings were published in the American Neurological Association's February journal, Annals of Neurology.
Ross said the connection between loss of smell and Parkinson's is not completely understood, but "nerve loss is known to take place in the olfactory structures of patients with the disease."
Smell could possibly be used as a screening test to identify people who would be at higher risk of Parkinson's disease, he said. They could then be enrolled in clinical trials to test medications that would prevent or slow progression of the disease, he said.
Other researchers are developing a battery of screening tests looking at loss of smell and other symptoms that occur before the classic features of Parkinson's, Ross said.
One, reported earlier by the Hawaii researchers, is constipation.
