Clinical features of Parkinson disease when onset of diabetes came first: A case-control study

Recent literature suggests that diabetes is a risk factor for Parkinson disease (PD). We investigated the clinical features of patients with idiopathic PD (IPD) in whom the onset of diabetes came first.

We designed a case-control study. From the cohort of all new patients with IPD free of vascular disease (n = 783) admitted and evaluated at our institute over a 3-year period (2007-2010), we included all the patients with a diagnosis of diabetes prior to PD onset (n = 89) and a control group (n = 89) matched (1:1) for gender, body mass index (± 1 kg/m(2)), and duration of PD (± 1 year). The Unified Parkinson's Disease Rating Scale (UPDRS) motor score was the primary endpoint.

At study entry, patients with diabetes were similar to controls in terms of most demographic, lifestyle, and general medical features with exception of statins (18% vs 3.4%; p = 0.003). However, diabetes was associated with higher UPDRS motor (22.3 ± 9.0 vs 19.3 ± 7.9; p = 0.019) and activities of daily living (9.7 ± 5.1 vs 8.3 ± 4.3; p = 0.049) scores, more severe Hoehn & Yahr staging (p = 0.009), and higher treatment doses of levodopa (mg/day, 448 ± 265 vs 300 ± 213; p < 0.0001; mg/kg/day, 5.8 ± 4.0 vs 3.8 ± 2.9; p < 0.0001).

Onset of diabetes before the onset of PD appears to be a risk factor for more severe PD symptoms. These findings support the hypothesis that diabetes has a role in the etiopathogenesis of PD. Neurologists should be aware of the potential impact of diabetes on overall PD management.