What the study found
The study was carried out across 8 countries, including the UK, in one of the largest studies of its type. It recorded the smoking status of 220,494 individuals aged 37-70 and whether they went on to develop Parkinson's. The information collected included the duration and intensity of smoking, and exposure to second hand smoke.
The researchers found that:
- former smokers were 20% less likely to develop Parkinson's, and this increased to 50% in current smokers
- both an increased frequency and duration of smoking was linked to a decreased risk of Parkinson's
- passive smoking was also shown to reduce risk
Despite the link with reduced risk, the researchers were clear that they wouldn't advise smoking due to the known adverse effects on general health.
Further research is still needed to better understand how smoking can reduce risk, with the hope that this may lead to future better treatments.
Dr Beckie Port, Research Manager at Parkinson's UK, comments:
"While this and many previous studies have presented evidence pointing towards smoking decreasing the risk of Parkinson's, this does not outweigh the fact that smoking increases the risk of other conditions, such as lung and mouth cancer, by a far greater extent.
"It is still unclear what chemical may be responsible, but it is interesting to note that nicotine-containing vegetables from the same botanical family as tobacco may also have protective effects. In one small study, these vegetables – which include tomatoes, potatoes, and peppers – were associated with a reduced the risk of Parkinson's compared to other vegetables.
"There is, however, a lack of evidence that nicotine replacement therapies, such as patches or gum, have the same effects on reducing Parkinson's risk."
The results were available online on 20 November in the International Journal of Epidemiology.