GI infections are associated with an increased risk of Parkinson’s disease

We have read with interest the recent publication of Perez-Pardo and colleagues1 reporting the role of the TLR4 in the gut–brain axis in Parkinson’s disease (PD). These findings prompted us to investigate the role of common GI infections (GIIs) in the pathogenesis of PD. In this prospective cohort study, we assessed the risk of PD in patients who previously suffered from GIIs compared with the control group not exposed to GIIs (table 1). At study entry (1 January 2005), the analysis sample from health claims data of the largest German health insurer consisted of2 28 485 individuals aged 50 years and older, which were followed for a mean time of 8.6 years (median=11.0 years; IQR=7.6 years). PD and GIIs were defined by ICD-10 codes as described in the supplementary material. Overall, 6195 individuals (2.7%) developed PD and 50 492 individuals (22.1%) were affected by any GII during the observation period between 2005 and 2015. The most frequent GIIs were those that caused infectious gastroenteritis and colitis of unspecified origin (IGCUs; 39 093 individuals, 17.1%), followed by viral intestinal infections (VIIs; 9328 individuals, 4.1%) and bacterial …