Korean researchers of diabetes have scientifically confirmed that people with type 2 diabetes mellitus have a higher risk of suffering from dementia, based on the National Health Insurance Service data.
Various global researches have confirmed that diabetes mellitus is associated with an increased risk of dementia. However, there have been few researches on how high the risk is in patients with type 2 diabetes mellitus.
To obtain a scientific result based on data, the team, led by Professors Kim Nah-hee at Korea University Ansan Hospital and Kim Seon-mee at Korea University Guro Hospital, aimed to analyze the incidence and risk factors for dementia and young-onset dementia among diabetic patients in Korea comprehensively.
Young-onset dementia is a term used to describe any form of dementia diagnosed in people under the age of 65.
The team used the NHIS data on a total of 1,917,702 participants with diabetes diagnosed between Jan. 1, 2009, and Dec. 31, 2012. They followed the participants until the date of dementia diagnosis or until Dec. 31, 2015.
The team evaluated the incidence and risk factors for all dementia, Alzheimer's dementia and vascular dementia by using the Cox proportional hazards analyses and compared the impact of risk factors on the occurrence of young-onset dementia and late-onset dementia.
As a result, during an average of 5.1 years of follow-up, the incidence of all dementia, Alzheimer's disease, or vascular dementia was 9.5, 6.8, and 1.3 per 1,000 people per year, respectively.
Young-onset dementia comprised 4.8 percent of all dementia occurrences, and the ratio of Alzheimer's disease or vascular dementia was 2.1 for young-onset dementia compared with 5.5 for late-onset dementia.
The team also found that smokers and subjects with lower income and body mass index (BMI), hypertension, dyslipidemia, vascular complications, depression, and insulin treatment developed dementia more frequently.
Vascular risk factors such as smoking, hypertension, and previous cardiovascular diseases were more associated with the development of vascular dementia than Alzheimer's disease, while low BMI and a history of stroke or depression had a stronger influence on the development of young-onset dementia than late-onset dementia.
In a related development, a separate study has found that patients with a history of hypoglycemia have a higher risk of dementia.
While type 2 diabetes mellitus is well known to be associated with an increased risk for dementia, the effects of hypoglycemia on dementia is still controversial.
Thus, the research team, led by Professor Han Seung-jin at Ajou University Hospital, evaluated whether hypoglycemia increases the risk for dementia in senior patients with type 2 diabetes mellitus.
The team used the Korean National Health Insurance Service Senior cohort, which includes 10 percent or more of the entire senior population of South Korea.
The team matched a total of 5,966 patients, who had ever experienced at least one episode of hypoglycemia, to those who had not experienced hypoglycemia. They assessed the risk of dementia through a survival analysis of matched pairs.
Patients with underlying hypoglycemic events had an increased risk for all-cause dementia, Alzheimer's dementia, and vascular dementia compared with those who had not experienced a hypoglycemic event.
According to the number of hypoglycemic episodes, the hazard ratio of dementia was 1.170 in patients with one hypoglycemic episode, 1.201 for those with two or three episodes, and 1.358 for those with more than three episodes.
In the subgroup analysis, hypoglycemia was associated with an increased risk for dementia in both sexes with or without type 2 diabetes mellitus microvascular or macrovascular complications.
"Our findings suggest that patients with a history of hypoglycemia have a higher risk for dementia," the team said. "This trend was similar for Alzheimer's dementia and vascular dementia, which are the two most important subtypes of dementia."
The first research was published under the title, “Incidence and Risk Factors for Dementia in Type 2 Diabetes Mellitus: A Nationwide Population-Based Study in Korea,” in the Diabetes & Metabolism Journal, while the second research was published under the title, “Hypoglycemia and Dementia Risk in Older Patients with Type 2 Diabetes Mellitus: A Propensity-Score Matched Analysis of a Population-Based Cohort Study,” in the same Journal