We would like to thank Melgoza et al. (1) for their interest in our article (2) and for suggesting the need for more analysis of the relationship of smoking and Parkinson disease (PD). They also suggested the importance of the cholinergic system in protection from PD and also stressed the need for discovery of novel drugs that target the cholinergic pathway to treat patients with PD and diabetes.
Although we did not analyze the relationship between smoking and PD, meta-analysis has reported that smoking is protective against PD, unlike in other chronic diseases (3). This could be because nicotine (one of the major components of tobacco) activates the anti-inflammatory cholinergic pathway, causing anti-inflammatory reactions by inhibiting the action of proinflammatory mediators (4). However, we have not yet reached a definitive conclusion about the protective role of smoking on PD and its mechanism.
In Korea, a result of investigating the effect of smoking on the risk of PD using data from the National Health Insurance system was recently reported (5). In this study, the authors investigated whether the influence of smoking and alcohol consumption on PD risk differs according to sex. They found that smoking and alcohol consumption independently reduced the risk of PD in both sexes.
Finally, it is necessary to consider the possibility of a reverse causality or selective mortality bias due to the clinical characteristics between smokers and nonsmokers. In the future, we hope that stronger evidence that will provide answers to these important issues will deepen our understanding of this relationship.
Duality of Interest. No potential conflicts of interest relevant to this article were reported.