Type 2 Diabetes Worsens Parkinson's Disease

Mitchel L. Zoler, PhD, for Medscape

November 08, 2021

Key Takeaways

  • Among adults with recently diagnosed Parkinson's disease, those with concomitant type 2 diabetes had at study entry more severe motor symptoms and a greater overall burden of nonmotor symptoms compared with patients without type 2 diabetes.

  • Patients with both Parkinson's disease and type 2 diabetes compared with those without type 2 diabetes had at baseline higher rates of depression and gait impairment, worse scores on measures of quality of life, and increased dependency.  

  • During an average follow-up of almost 38 months, patients with both Parkinson's disease and type 2 diabetes had, compared with those without type 2 diabetes, significantly increased progression of motor symptoms and a higher risk for developing gait impairment and mild cognitive impairment.

Why This Matters

  • The findings suggest that the presence of type 2 diabetes results in more severe symptoms in patients with Parkinson's disease and worsens long-term outcomes of these patients.

  • This is the first study to report the impact of type 2 diabetes on nonmotor symptoms in people with Parkinson's disease.

  • The findings suggest that insulin resistance — a potentially modifiable state with multiple possibilities for intervention — is a novel target for mitigating parkinsonian symptoms, neurodegeneration, and progression to disability and dementia.

Study Design

  • The study included 1930 adults with recent-onset Parkinson's disease (enrolled within 3.5 years of first diagnosis) entered into a UK-based prospective registry, Tracking Parkinson's. 

  • Comparison of 167 of these patients (9%) who also had a diagnosis of type 2 diabetes and the 1763 (91%) without type 2 diabetes.

Key Results

  • Patients with type 2 diabetes had been diagnosed with Parkinson's disease for an average of about 16 months prior to entering the registry, similar to those without type 2 diabetes, but had consistently more severe symptoms of Parkinson's disease.

  • Average scores on the Movement Disorders Society Unified Parkinson's Disease Rating Scale and the Non-Motor Symptoms Scale were significantly worse among patients with type 2 diabetes.

  • Concurrent type 2 diabetes was significantly and independently associated with greater gait impairment (odds ratio [OR] 2.91; P = .002), depression (OR, 1.62; P = .015), and loss of independence (OR, 2.08; P = .001) relative to the PD only group, after adjustment for confounding variables.


  • Biases introduced by patient dropouts.

  • Type 2 diabetes identified by self-reports and medication data.

  • No detailed data on type 2 diabetes such as duration, severity, and comorbidities.

  • Hard to account for medication changes during follow-up.


  • Tracking Parkinson's is primarily funded by Parkinson's UK.

  • Dilan Athauda, PhD, has received honoraria from Bial Pharma.

  • Several of the co-authors have received honoraria and grants from various pharmaceutical companies.

This is a summary of a preprint research study written by Dilan Athauda, PhD, from University College London, and co-authors on MedRxiv provided to you by Medscape. This study has not yet been peer-reviewed. The full text of the study can be found on MedRxiv.org.

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