Impact of type 2 diabetes mellitus on severity of Parkinson's disease: a cross-sectional study

Background and objectives. Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms that significantly impact quality of life. This study aimed to investigate whether the presence of type 2 diabetes mellitus (T2DM) influences the clinical severity and manifestations of PD across motor and non-motor domains. Materials and methods. This cross-sectional study compared 80 PD patients (40 with T2DM and 40 without) at the Neurology Department of Mansoura University Hospital, Egypt. Demographic and clinical characteristics were documented. The Unified Parkinson's Disease Rating Scale (UPDRS), Montreal Cognitive Assessment (MoCA), Hamilton Anxiety and Depression Scales, and Schwab and England Activities of Daily Living Scale were assessed in all participants. Results. PD patients with T2DM exhibited significantly more severe motor impairments, including substantial gait problems (p = 0.003) and reduced independence (p < 0.001). The T2DM group showed higher scores across UPDRS components: non-motor experiences (p < 0.001), motor experiences (p = 0.001), and motor examination (p = 0.003). While cognitive function was comparable, T2DM patients demonstrated significantly higher anxiety levels (p = 0.014) and more advanced disease with higher Hoehn and Yahr staging (p = 0.004), despite similar disease duration and levodopa equivalent daily doses. Conclusions. T2DM is associated with more severe manifestations of PD across multiple domains, suggesting significant interaction between the two conditions. These findings emphasize the importance of early screening and aggressive management of T2DM in PD patients to optimize clinical outcomes.