Importance: Type 2 diabetes (T2DM) is an established risk factor for developing Parkinson's disease (PD) but its effect on disease progression is not well understood.
Objective: To examine the effects of co-morbid T2DM on Parkinson's disease progression and quality of life.
Design: We analysed data from the Tracking Parkinson's study, a large multi-centre prospective study in the UK.
Participants: The study included 1930 adults with recent onset PD, recruited between February 2012 and May 2014, and followed up regularly thereafter.
Exposure: A diagnosis of pre-existing T2DM was based on self-report at baseline. After controlling for confounders, an evaluation of how T2DM affects PD was performed by comparing symptom severity scores; and analyses using multivariable mixed models was used to determine the effects of T2DM on Parkinson's disease progression.
Main Outcomes and Measures: The impact of T2DM on Parkinsons disease severity was derived from scores collected using the Movement Disorders Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Non-Motor Symptoms Scale (NMSS), Montreal Cognitive Assessment (MoCA), Questionnaire for impulsive-compulsive disorders in PD (QUIP), Leeds Anxiety and Depression Scale (LADS), and Schwab and England ADL scale.
Results: We identified 167 (8.7%) patients with PD and T2DM (PD+T2DM) and 1763 (91.3%) with PD without T2DM (PD). Patients with T2DM had more severe motor symptoms, as assessed by MDS-UPDS III 25.8 (0.9) vs 22.5 (0.3) p=0.002, had significantly faster motor symptom progression over time (p=0.012), and T2DM was an independent predictor for the development of substantial gait impairment (HR 1.55, CI 1.07-2.23, p=0.020). Patients were more likely to have loss of independence (OR 2.08, CI 1.34-3.25, p=0.001); and depression (OR 1.62, CI 1.10-2.39, p=0.015), and developed worsening mood (p=0.041) over time compared to the PD group. T2DM was also an independent predictor for the development mild cognitive impairment (HR 1.7, CI 1.24-2.51, p=0.002) over time
Conclusions and relevance: T2DM is associated with faster disease progression in PD, highlighting an interaction between these two diseases. As it is a potentially modifiable, metabolic state, with multiple peripheral and central targets for intervention, it may represent a target for ameliorating parkinsonian symptoms, and progression to disability and dementia.
The Impact of Type 2 Diabetes in Parkinson's Disease
