Investigating the causal effect of calcium level on motor, cognitive, composite symptoms of PD, and PD itself using Mendelian Randomization

Parkinson’s Disease (PD), the second-most common neurodegenerative disorder, is increasing in prevalence worldwide with the phenomenon of world population ageing. Common symptoms of PD including rest tumor, dementia, and Lewy bodies can severely deteriorate patients physically and mentally; however, factors causing PD and the treatment to cure PD is still under investigation. Calcium, which is a chemical responsible for muscle contractions, has been associated with some PD symptoms such as formation of Lewy bodies and muscle rigidity. While studies that show association between calcium and PD are abundant, there is no study that specifically focuses on the causal relationship between them: hence, in this study, we aimed to examine the causal relationship between calcium level in patients and motor, cognitive, composite symptoms of PD, and PD itself using the Mendelian Randomization (MR) method. Other studies that used calcium-blocking drugs such as isradipine, mitochondrial calcium inhibitors, and MUC blockers to demonstrate the impact of calcium-blocking treatment on PD patients led us to take calcium as an exposure in our study as well. After constructing MR under both highly stringent and less stringent conditions using different p-values, we were able to observe whether there is a causal relationship identified. The result of our study reveals that there is no direct causal relationship between calcium and PD or PD symptoms, even though there might be a possibility that calcium indirectly induces PD.