People with Parkinson鈥檚 disease are less likely to be smokers and coffee drinkers than their healthy siblings, according to a study of family members. The finding adds to a growing body of evidence that some substance in tobacco might protect the brain against this devastating neurological disorder and sheds new light on coffee鈥檚 effects on the disease.
Researchers say the study provides new evidence that the causes of Parkinson鈥檚 vary. They also stress that the negative health effects of smoking far outweigh any protective effect the substance might have against this neurodegenerative disease.
Parkinson鈥檚 disease, which generally strikes people over the age of 50, leads to a loss of coordination, dementia and may result in early death.
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For decades, scientists have found evidence suggesting that smokers are less likely to develop this illness than non-smokers. But experts believe that genes can influence one鈥檚 risk of developing Parkinson鈥檚, and the vast majority of these studies involved participants who were unrelated and therefore genetically dissimilar.
To control for this genetic variability, William Scott of the University of Miami in Florida, US, and his colleagues studied the smoking and coffee-drinking habits of Parkinson鈥檚 patients and their family members.
Close relatives
They recruited 356 Parkinson鈥檚 patients and 317 of their close relatives, such as siblings. All of the relatives had passed the age at which their family member with Parkinson鈥檚 had first shown signs of the disease.
The team found that the Parkinson鈥檚 patients were about 40% less likely to have ever smoked than their healthy relatives, and 50% less likely to be long-term smokers, with roughly 10% smoking for more than 30 years, compared with 15% of their healthy counterparts.
Of the healthy relatives, about 40% consumed an average of three or more cups of coffee a day over their lifetime. By contrast, those with Parkinson鈥檚 were about 40% less likely to report drinking this much coffee.
Exactly why smoking and consuming coffee had an inverse association with Parkinson鈥檚 disease remains largely unclear.
Dopamine link
One possible mechanism involves a signalling chemical in the brain called dopamine. The death of dopamine-producing cells in the brain appears to drive the progression of Parkinson鈥檚 disease, and both smoking and drinking coffee can raise levels of the chemical.
快猫短视频s have also found some evidence that a substance in tobacco smoke may boost dopamine levels by blocking the production of toxins that poison dopamine-producing cells (see Why the wicked weed wards off Parkinson鈥檚).
But Scott cautions that the relationship between Parkinson鈥檚 and smoking may not be a simple one of cause and effect. The biology of certain people鈥檚 brains who develop Parkinson鈥檚 disease may simply make them less likely to become addicted to cigarettes, he says.
Smoking risks
Scott says the new research lends support to the idea that there are multiple ways that Parkinson鈥檚 can strike.
A variety of different genetic mutations are associated with Parkinson鈥檚, and only some of them may have any kind of smoking link. For example, a Parkinson鈥檚-related gene mutation called NOS2A does not appear linked to the habit 鈥� patients with the mutation were just as likely as their close relatives to report regularly smoking and drinking coffee.
Scott emphasises that the results of his study should not give anyone an excuse to start smoking. He says that the well-established risks of smoking 鈥� such as developing lung cancer or having a heart attack 鈥� 鈥渁bsolutely鈥� outweigh any potential protection it might offer against Parkinson鈥檚.
鈥淎nd relative to lung disease and heart disease, Parkinson鈥檚 disease is far less common,鈥� he adds.
Journal reference: Archives of Neurology (vol 64, p 576-580)
