Earlier studies have found a surprising link between smoking and reduced Parkinson's risk. However these studies were not conducted in related family members. Parkinson's patients are more likely to be non-smokers and drink scanty amounts of coffee. However researchers stressed the negative effects of smoking were far more lethal than just conferring a protective effect against Parkinson's disease.

Parkinson's is a condition that causes progressive loss of nerve cell function in a part of the brain responsible for controlling muscle movements. The exact cause of Parkinson's disease remains unknown, but a strong link to the neurotransmitter dopamine does exist.

Dopamine normally sends signals that help coordinate movements. In Parkinson's, the neurons that make dopamine die or do not function properly. Exposure to pesticides is also strongly linked with the disease.

Patients suffering from Parkinson's disease are generally over 60. The condition leads to a progressive loss of coordination and dementia. Other signs include depression, sleep problems or trouble chewing, swallowing or speaking. Parkinson's can also lead to an early death. Some studies have found a genetic link to Parkinson's prompting researchers to postulate that family members face a greater risk of developing the disease.

Previous studies included participants who were unrelated and thus genetically different from the patients. Lead researcher William Scott, currently of the University of Miami and formerly from Duke, recruited 356 Parkinson's sufferers and 317 of their close relatives. Around 235 Parkinson's patients were male, while 139 healthy relatives were also of the same gender.

The average age of the patients with Parkinson's disease was 66 years. All family members had surpassed the age at which their relative had first shown signs of Parkinson's disease. The details of the study appear in the April issue of Archives of Neurology.

On comparing smoking and coffee consumption among Parkinson's patients and their relatives, researchers said:
* Parkinson's patients were 40 percent less likely to have ever smoked than their healthy relatives.

* They were also 50 percent less likely to be long-term smokers. Only 10 percent had smoked over the last three decades, while 15 percent of the healthy participants were regular smokers.

* Parkinson's patients were 42 percent less likely to be high-level coffee drinkers, while 40 percent of their healthy relatives consumed three or more cups of coffee a day over their lifetime.

* No link was found between nonsteroidal anti-inflammatory drugs (NSAIDs) use and Parkinson's disease.

The researchers were also unable to specify exactly why smoking and consuming coffee lowered the risk of Parkinson's in family members.

One theory is that both smoking and drinking coffee can raise levels of dopamine in the brain. This chemical is deficient in Parkinson's sufferers because the nerve cells that produce it are defective. Researchers have earlier found a substance in tobacco smoke boosts dopamine levels in the brain.

"Our findings represent the first examination of the association between Parkinson's disease and caffeine in a case-family control setting, where cases were well matched to family controls on many unmeasured genetic and environmental factors," the researchers write.

Dr Scott says the new study is further evidence of the multi-factorial nature of Parkinson's disease. "Given the complexity of Parkinson's disease, these environmental factors likely do not exert their effects in isolation, thus highlighting the importance of gene-environment interactions in determining Parkinson's disease susceptibility," he said.

It is likely that smoking and caffeine might modify the genetic factors involved in Parkinson’s disease and exert a protective effect among family members of Parkinson's sufferers.

Researchers caution that consumers must not tank up on cigarettes and coffee simply to avert Parkinson's disease. The adverse effects of these two habits far outweigh any potential benefits attributed to them. As Dr Scott says, "Relative to lung disease and heart disease, Parkinson's disease is far less common.”

Parkinson's disease affects 1.5 million Americans with 60,000 new cases diagnosed each year.There is no cure for the disease although medicines improve the quality of life.