Dementia is associated with insulin resistance in patients with Parkinson's disease

Parkinson's disease is a neurodegenerative disorder involving the basal ganglia. Type-2 Diabetes Mellitus is an important risk factor for Alzheimer disease and vascular dementia. However, the association between Parkinson's disease and Diabetes Mellitus is controversial.

To investigate glucose metabolism abnormalities in 110 Parkinson's disease patients with and without dementia.

We evaluated Insulin Resistance, glucose and insulin levels after a 2-h-oral-glucose-tolerance-test in 53 Parkinson's disease with dementia and 57 with Parkinson's disease without dementia, with normal fasting glucose.

BMI, waist circumference, fasting glucose and insulin values, HbA1c, triglycerides, blood lipid profile, depression rating, educational levels, levodopa-dosage and antipsychotic use were similar in both groups. Disease duration and motor impairment were higher in patients with Parkinson's disease and dementia group. After 2-h-oral-glucose-tolerance-test, the prevalence of glucose metabolism abnormalities was significantly higher in group with Parkinson's disease and dementia group (p=0.03). The insulin resistance was present in 62% patients with Parkinson's disease with dementia, of whom 30% had also impaired glucose tolerance, 5,6% newly diagnosed Diabetes Mellitus and 26% only Insulin Resistance. These percentages were significantly higher in group with Parkinson's disease and dementia, also after adjustment for disease duration and motor disability.

Our study suggests that PD patients with dementia are two times more likely to have insulin resistance than patients with PD.