Older patients with IBD might have higher risk of Parkinson’s disease

We read with interest the study by Villumsen et al 1 which reported that patients with IBD had a 22% increased risk of Parkinson’s disease (PD) compared with non-IBD individuals. The study supported the theory that intestinal environment could influence the function of central nervous system which was also called the gut–brain axis. Recently, a meta-analysis by Zhu et al 2 suggested that the overall risk of PD in patients with IBD was significantly higher than controls (OR 1.41; 95% CI 1.19 to 1.66). However, only four studies were included in the meta-analysis. We also noticed a case–control study by Camacho-Soto et al 3 reporting that the risk of PD was inversely associated with IBD (OR 0.85; 95% CI 0.80 to 0.91), which was not …