UK
A six-decade follow-up study of nearly 30,000 British male doctors found that those who smoked tobacco when the study began in 1951 had a 30% lower risk of death from Parkinson’s disease (PD), while those who continued to smoke had 40% lower risk, according to a report published in the May 5 online edition of Neurology.
The cohort study, which was followed up for 65 years, does not prove cause and effect — that smoking tobacco protects against PD – but it adds to previous findings that suggest that tobacco smoking is beneficial when it comes to the risk of developing PD. Researchers suspect that the nicotine found in tobacco may have a protective effect.
The authors noted that a 2015 meta-analysis of observational studies reported that current smoking was associated with 60% lower risk of PD, but cautioned “there is substantial uncertainty about the causal relevance of this inverse association.”
The new analysis was based on information on 29,737 doctors. After the researchers did statistical adjustments for age-at-risk, current smokers at baseline had a 30% lower risk of PD, and the current smokers had a 40% lower risk of PD compared with doctors who never smoked.
The investigators concluded “in contrast with previous suggestions, the present report demonstrates a causally protective effect of current smoking on risk of PD.”
A high response rate to the repeated surveys, and the fact that they used several statistical models to account for changes in smoking habits, reverse causality, and age-at-risk of PD — each of which yielded consistent results.