Effect of vitamin D and other indicators of phosphorus-calcium metabolism on cognitive functions and quality of life in patients with Parkinson's disease

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Parkinson’s disease (PD) is a multifactorial neurodegenerative disease. Consequently, there has been growing interest in identifying early preclinical disease symptoms and searching for their laboratory markers in recent decades.Objective: to studythe relationship between vitamin D levels, phosphorus-calcium metabolism and clinical manifestations of PD.Patients and methods. Serum levels of total vitamin D (VD), as well as total calcium, ionized calcium, alkaline phosphatase (AP), inorganic phosphorus, and parathyroid hormone (PTH) were assessed in 138 patients with PD. The severity of the disease was verified according to the Hoehn-Yar criteria, the clinical symptoms of the disease were verified using the Unified PD Rating Scale (UPDRS), the evaluation also included the quality of life (QoL) scales for patients with PD (PDQ-39), anxiety and depression (HADS), and Beck depression inventory, assessment of cognitive functions (CF) according to MoCA. Then, we analyzed the effect of vitamin D levels and other indicators of phosphorus-calcium metabolism on the severity of PD clinical symptoms.Results and discussion. Patients with PD had a significant impact of phosphorus-calcium metabolism on CF, assessed by MoCA scale and the PDQ-39 subscale “Cognitive functions”. A joint direct impact of vitamin D levels (β=0.111; p=0.002), PTH (β=0.02; p=0.037) and the indirect effect of AP (β=-0.028; p=0.027) on CF was revealed. A direct effect of the level of inorganic phosphorus (β=5.932; p=0.001) and AP (β=0.055; p=0.025) on the QoL of patients with PD was observed.Conclusion. Cognitive decline in PD patients is directly related to vitamin D and PTH levels. At the same time, the lower the QoL of patients with PD, the lower the serum vitamin D level was, serving as an early predictor of cognitive decline in patients with PD.