Anemia and the risk of Parkinson's disease in Korean older adults: A nationwide population-based study.

Evidence of the association between anemia and risk of PD (Parkinson's disease) have been accumulating. This study aimed to examine the relationship between anemia and risk of PD in Korean older adults. Korean adults aged 50 years or older who participated in the Korean National Screening Program (n = 12,342,278) between 2009 and 2013 were followed until 2015. Cox proportional hazards regression models were used to calculate the hazard ratio (HR) of PD, and participants were followed for a mean period of 5.0 years. At the end of follow-up, 3,844 adults were diagnosed with PD. After adjusting for potential confounders, participants with anemia had decreased risk of PD compared to adults without anemia (adjusted HR (aHR) 0.894, 95% CI: 0.809-0.989). Furthermore, aHR of PD was 0.698 (95% CI: 0.546-0.891) in moderate to severe anemia and 0.938 (95% CI: 0.843-1.044) in mild anemia. The protective effect of anemia was also more profound in men (aHR 0.888, 95% CI: 0.774-1.02) than in women (aHR 0.905, 95% CI: 0.782-1.048). In conclusion, anemia was associated with lower risk of PD, particularly for patients with moderate to severe anemia. Our study suggests that further studies may be needed to clarify the relationship between anemia and PD.