People from families prone to Parkinson's who drink coffee or smoke are less likely to develop the disease, researchers said on Monday in a finding that reinforces earlier observations and offers potential paths to treatment.
The researchers doubt that smoking and caffeine protect from Parkinson's, but say the information offers clues about how environment works with genes to cause disease.
Dr. William Scott of the University of Miami school of medicine, who led the study, said the findings point clearly to dopamine -- a message-carrying chemical in the brain that falls to low levels in Parkinson's.
"Dopamine is important because both smoking and drinking caffeine affect dopamine in the brain," Scott said in a telephone interview. Other researchers had noted that both smoking and drinking coffee seemed to reduce the risk of Parkinson's, but no one had tracked it in families prone to Parkinson's.
When a disease runs in families, it suggests that certain genes are causing it. "We need to consider these environmental associations while looking for genes that are involved in Parkinson's," Scott said.
Writing in the Archives of Neurology, Scott and colleagues said they studied 356 Parkinson's disease patients and 317 family members without the disease. "Based on this paper we find that people who had Parkinson's disease were 40 percent less likely to say that they had ever smoked 100 cigarettes than their unaffected family members.
A similar reduction was seen in the likelihood with coffee," Scott added. "It seems that people with Parkinson's are less likely to have done these things over their lives -- to have smoked or to have consumed fairly large amounts of caffeine."
Possible Protection: The researchers say they cannot yet say with certainty what effects coffee and cigarettes may have on the brain. Mark Stacy of Duke University in North Carolina, who worked on the study, said it remains possible that coffee or cigarettes protect the brain. But it is also likely, his colleagues said, that something else is going on. Perhaps people who later develop Parkinson's respond differently to the effects of caffeine and cigarettes.
"There is this notion, and it makes a lot of sense, that folks who are going to have have Parkinson's disease have lower levels of dopamine," said Duke neurologist Dr. Burton Scott, who also worked on the study. "Those with higher levels of dopamine may be more likely to enjoy caffeine," he added. The same team is now trying to pin down more of the genes associated with Parkinson's.
"I wouldn't make any lifestyle changes based on this, but I'd also think that with drinking my morning cup of coffee this morning that, hey there's at least one good thing that comes from this," William Scott said. Parkinson's disease is caused when brain cells that produce dopamine die. The disease is progressive, affecting about 1 per cent of people older than 65.
Symptoms start out with shaking and can progress to paralysis. There is no cure, although a number of drugs can make symptoms better for a time. Exposure to pesticides is strongly linked with disease risk.