A recent population-based cohort study offers more insight into the link between glycemic status and the risk for Parkinson’s Disease.
Uncontrolled diabetes is associated with many widely known comorbidities; however, several studies have additionally found a potential association between hyperglycemia and conditions such as Parkinson‘s disease (PD). These have suggested that insulin resistance and glycemic status may significantly affect the development and progression of PD. Although a clear link between these conditions has not been established, focusing on how they are related is imperative due to the lack of curative therapies available for PD and its detrimental effects on quality of life.
A recently published population-based cohort study aimed to determine whether glucose tolerance, diabetes duration, and comorbidities increased the risk of PD, using data from the National Health Insurance Service database in Korea. The analysis included patients 40 years or older without a previous history of PD who were part of the NHIS health examinations between January 2009 and December 2010. A total of 8,443,351 participants were included in the study and divided into groups based on glycemic status. The study included 5,025,010 participants without diabetes (FG < 100 mg/dL), 2,110,252 participants with impaired fasting glucose (FG 100-125 mg/dL), 753,796 patients with a history of diabetes for less than five years, and 554,293 patients with long-standing diabetes for five years or more. Researchers followed participants until December of 2016, and the mean observation period was 6.3 years.
Baseline characteristics among the groups were noted to be different. Participants in the impaired fasting glucose (IFG) and diabetes groups had a higher mean age, larger waist circumference, higher fasting blood glucose levels, a higher proportion were men, and a higher percentage had comorbidities, compared to the non-diabetes group. However, other characteristics like BMI were similar among all groups. This study found that the incidence of PD was higher in patients with diabetes than in non-diabetic participants (1.134 per 1000 person-years compared to 0.558 per 1000 person-years, respectively). Additionally, when comparing all subgroups in the study, those with a diabetes duration of five years or more showed a higher incidence of PD than other groups (p=0.001). Analysis of the cumulative prevalence of PD using the Kaplan-Meier curve showed that the incidence of PD increased as glucose intolerance and diabetes duration increased. The prevalence of PD was higher among participants with diabetes for five years or more, followed by those who had diabetes for less than five years and those with IFG. The log-rank test also showed that the incidence of PD among the subgroups was significantly different (p=0.001).
Evaluation of the unadjusted and adjusted hazard ratio (HR) also showed similar results. Compared to participants without diabetes, people with diabetes had a higher risk of developing PD (HR= 2.036). Further adjusting for age and sex (model 2) and BMI, smoking, alcohol use, and physical activity (model 3) in these two groups showed a higher risk of PD in patients with diabetes (aHR model 2= 1.389; aHR model 3= 1.372). A comparison of the four subgroups included in the study further exposed that the risk of PD was higher as hyperglycemia and diabetes duration increased. The unadjusted and adjusted HR for those with a diabetes duration of five years or more was much higher compared to other groups (HR= 2.933, aHR model 2= 1.646, aHR model 3= 1.618). Participants with diabetes for less than five years had the next highest risk (HR=1.657), followed by those with impaired fasting glucose (HR= 1.214). These results were also consistent when assessing for the competing risk of death. Further analysis on the effect of comorbidities showed that although CVD, cerebrovascular disease and CKD increased the risk of Parkinson‘s disease, the presence of diabetes itself was an independent risk factor for the development of PD since a higher risk was seen in patients with diabetes even in the absence of comorbidities.
This study provides further evidence that diabetes increases the risk of Parkinson‘s disease, but more importantly, it conveys new evidence on how impaired fasting glucose may have a similar effect. Even though there is still no cure for this condition, this study highlights the importance of glycemic control and its potential role in reducing the risk of Parkinson‘s disease. Further studies should evaluate the causal association between these two conditions and how glycemic control improves these patients‘ outcomes.
- Diabetes and prediabetes were both shown to increase the risk of PD, with prolonged exposure to hyperglycemia showing the most significant effect.
- Comorbidities such as CVD, cerebrovascular disease, and CKD were shown to increase the risk of PD; however, diabetes was found to be an independent risk factor.
- Glycemic control and diabetes prevention may play an essential role in decreasing the risk of developing PD.
Rhee, Sang Youl, et al. “Association Between Glycemic Status and the Risk of Parkinson Disease: A Nationwide Population-Based Study.“ Diabetes Care, [Publish Ahead of Print, July 2020], doi: 10.2337/dc19-0760
Leyany Feijoo Ramos, PharmD. Candidate, LECOM School of Pharmacy