Influence of current and previous smoking on current phenotype in Parkinson's disease

Although an inverse correlation between smoking and Parkinson's disease (PD) has been reported, research into the effect of smoking on current clinical progression remains limited for PD patients. Elucidation of a specific PD population who would benefit from smoking is challenging.

We evaluated 110 consecutive PD patients (mean age; 71.0 ± 8.0 years) at a single neurology clinic between 2010 and 2018. The association with smoking status was evaluated in sex- and age-matched controls (non-PD). This study assessed the impact of previous smoking exposure on the outcome of current PD-related parameters, along with any confounders, in addition to assessing fluctuation of parkinsonism induced by smoking exposure.

The current smoking rate was significantly lower in PD versus non-PD (5.5% vs. 15.5%, P = 0.026), while there were similar rates between former and never smokers. Among the former smokers, most PD patients (97.3%) quit smoking prior to the onset of PD. There were no differences between PD patients with and without a history of smoking for current clinical parameters. Three PD patients with the mean onset age of 51.0 ± 5.3 y reported transient deterioration of their parkinsonism when smoking. Negative mood during cigarette smoke exposure was significantly increased over the entire life in PD patients with a history of smoking than those without (p < 0.001).

Although previous smoking history reportedly had a neuroprotective effect prior to onset, the association between the previous history and current phenotype in PD was not visible in the present study. However, the possibility that current nicotine intake might modify the parkinsonism deterioration will need to be further evaluated, especially in non-elderly patients. Cigarette smoke-related negative mood could be a confounder for quitting smoking in PD patients.