Both type 2 diabetes and neurodegenerative diseases are common in the elderly population. Growing evidence indicates a strong link between type 2 diabetes and neurodegenerative diseases such as Alzheimer's disease.

A population-based 10-year follow-up study was conducted using the Korean National Health Information Database for 2002–2015. We used a retrospective cohort study design to investigate the association of type 2 diabetes with incidence of neurodegenerative diseases. The study cohort included the type 2 diabetes group (n=155,459) and the control group (n=155,459), aged 65 years or over, who were matched similarly for age, sex, and comorbidities. Cox proportional hazards models were used to obtain multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) for incidence of neurodegenerative diseases.

At the end of the follow-up period, the frequency of neurodegenerative diseases occurrence was significantly higher in the type 2 diabetes group (32.9%) than in the control group (28.7%) (χ²=622.53, p<0.001). The incidence rate of neurodegenerative diseases in the type 2 diabetes and control groups was 44.68 (95% CI: 44.29–45.07) and 36.89 (95% CI: 36.55 to 37.24) cases per 1,000 person-years at risk, respectively. The overall incidence of neurodegenerative diseases was higher in the type 2 diabetes group than in the control group (HR: 1.23, 95% CI: 1.22–1.25, p<0.001).

Our data showed that increased incidence of neurodegenerative diseases in subjects with type 2 diabetes and a positive association between type 2 diabetes and neurodegenerative diseases. These results suggest that type 2 diabetes is associated with an increased risk of neurodegenerative diseases in elderly Koreans.