This association was first observed in a 1959 study by the U.S. Public Health Service on tobacco smoking and mortality. After analyzing almost 200,000 veterans, researchers found that smokers had a 64% reduced risk of dying from Parkinson’s compared to non-smokers[4].
While epidemiological studies can’t demonstrate that smoking is indeed the cause of the reduced risk, additional evidence supports a causal link.
For example, the apparent protection of smoking increases with the dose and the years the person has been smoking[5]. Conversely, people who quit smoking have a higher risk of Parkinson’s than active smokers, although still lower than that of people who never smoked. Some research has shown that passive smokers show a risk reduction similar to that of active smokers[6], although the evidence in this regard is conflicting.
3 – Mappin-Kasirer et al. (2020) Tobacco smoking and the risk of Parkinson disease: A 65-year follow-up of 30,000 male British doctors. Neurology.
https://www.sciencedirect.com/science/a ... 2216302307
4 – Harold F. Dorn (1959) Tobacco consumption and mortality from cancer and other diseases. Public Health Reports.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1929281/
5 – Chen et al. (2010) Smoking duration, intensity, and risk of Parkinson disease. Neurology.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2836869/
6 – Nielsen et al. (2012) Environmental tobacco smoke and Parkinson disease. Movement Disorders.
https://www.ncbi.nlm.nih.gov/pmc/articl ... 329721.pdf