Risk of lung cancer in Parkinson's disease

Recently, growing evidence has revealed the significant association between Parkinson's disease (PD) and cancer. However, controversy still exists concerning the association between PD and lung cancer. A comprehensive article search for relevant studies published was performed using the following online databases: PubMed, Web of Science and Embase up to August 31, 2016. The pooled risk ratio (RR) and their 95 % confidence intervals (CI) were calculated using the method of inverse variance with the random-effects model. Fifteen studies comprising 348,780 PD patients were included in this study. The pooled result indicated that patients with PD were significantly associated with a decreased risk of lung cancer (RR: 0.53, 95% CI: 0.41-0.70, P < 0.001). In addition, subgroup analyses performed in Western population also confirmed the significant inverse relationship between PD and risk of lung cancer (RR: 0.48, 95% CI: 0.39-0.60, P < 0.001). In the subgroup analysis, a reduced risk of lung cancer in PD patients from Western population was consistent regardless of study design, gender, or study quality. In conclusion, PD patients were significantly associated with a reduced risk of lung cancer in Western population. The relationship between them in Asian population needs to be confirmed by future studies.