Figure 3: Analyses of subgroups relating IBD to PD. Subgroup analyses by temporal relationship revealed that IBD occurrence was significantly higher before or after PD diagnosis. Crohn’s disease and ulcerative colitis were both linked to elevated PD risk. There was no significant difference in risk in the sex-specific analysis, but older adult patients with IBD had a possibly increased PD risk compared with younger adult patients. IBD patients who were never exposed to anti-tumor necrosis factor-α (TNF-α) or thiopurines also had a possibly higher risk of developing PD compared with those who were exposed to these treatments. aHR: Adjusted hazard ratio; aRR: adjusted risk ratio; cRR: crude risk ratio; IBD: inflammatory bowel diseases; PD: Parkinson’s disease..