In recent years, an emerging body of evidence has forged links between Parkinson's disease (PD) and type 2 diabetes mellitus (T2DM). In observational studies, those with T2DM appear to be at increased risk of developing PD, as well as experiencing faster progression and a more severe phenotype of PD, with the effects being potentially mediated by several common cellular pathways. The insulin signalling pathway, for example, may be responsible for neurodegeneration via insulin dysregulation, aggregation of amyloids, neuroinflammation, mitochondrial dysfunction and altered synaptic plasticity. In light of these potential shared disease mechanisms, clinical trials are now investigating the use of established diabetes drugs targeting insulin resistance in the management of PD. This review will discuss the epidemiological links between T2DM and PD, the potential shared cellular mechanisms, and assess the relevant treatment options for disease modification of PD.

Background: Many countries have implemented drastic measures to fight the COVID-19 pandemic. Restrictions and diversion of resources may have negatively affected patients with Parkinson's disease (PD). Our aim was to examine whether COVID-19 had an impact on access to PD medication by region and income. Methods: This study was conducted as part of a survey sent to members of the Movement Disorders Society focusing on access to PD medication globally. Results: Of 346 responses, 157 (45.4%) agreed that COVID-19 had affected access to PD medication, while 189 (54.6%) disagreed. 22.8% of high-income and 88.9% of low-income countries' respondents agreed that access to PD medication was affected by COVID-19. 59% of all 'yes' respondents reported increased disability of patients as an impact. Conclusions: Access to PD medication is likely to have been affected by COVID-19 and result in deterioration of patients' symptomatic control. Resource-poor countries appear to be disproportionately affected compared to more affluent countries.