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Study links younger age of onset of type 2 diabetes to increased risk of dementia

People who develop type 2 diabetes at a younger age have an increased risk of dementia, according to a new study funded in part by NIA and published in JAMA on April 27.An older adult checks their blood glucose level with a home glucose meter.

Type 2 diabetes is a serious chronic condition that affects many older adults. This disease is becoming more common and is occurring at younger ages. Previous studies have shown that diabetes is associated with an increased risk of dementia. However, these studies did not address whether the age at which a person is diagnosed with type 2 diabetes influences this risk.

For this new research, scientists led by a team at the Université de Paris explored the link between age of onset of type 2 diabetes and the risk of dementia. They examined data from the Whitehall II Study, a long-term longitudinal study of health in British government employees. Participants were between the ages of 35 and 55 when they enrolled. The researchers used results from blood tests conducted every four to five years and electronic health records (EHRs) spanning about 32 years to identify participants who had type 2 diabetes or were taking medicine to treat this condition. The team used EHRs to determine which participants were later diagnosed with dementia.

Out of 10,308 participants, a total of 639 were later diagnosed with dementia. Of the 1,710 diagnosed with type 2 diabetes, 153 were later diagnosed with dementia. The researchers found that, people who were diagnosed with diabetes between 65 and 70 years old were 24% more likely to have dementia than people who did not have type 2 diabetes at age 70. Likewise, people who were diagnosed with diabetes between ages 60 and 64 and before age 60 were each 24% more likely to have dementia than people who were diagnosed with diabetes five years later. Participants who were diagnosed with diabetes after age 70 did not have an increased risk of dementia. Interestingly, people who had pre-diabetes, a condition in which a person has high blood sugar levels but not high enough to be diagnosed with diabetes, did not have a higher risk of dementia.

Results showed that participants who were diagnosed with type 2 diabetes at a younger age also had dementia at a younger age. Participants with diabetes and cardiovascular diseases such as coronary heart disease, heart failure, or stroke had an even higher risk of dementia. Because the EHRs did not indicate which type of dementia the participants had, the researchers could not determine whether type 2 diabetes was more strongly linked to specific types of dementia.

The researchers believe that in people with type 2 diabetes, insulin resistance, problems with a person’s blood vessels, and frequent changes in blood sugar levels over several years might cause problems with blood flow and metabolism in the brain. Signs of dementia usually start more than a decade before diagnosis, and further research is needed to understand how type 2 diabetes affects dementia progression.

This research was supported in part by NIA grants R01AG056477 and RF1AG062553.

These activities relate to NIH’s AD+ADRD Research Implementation Milestone 2.S, “Determine interrelationships among cerebro- and cardiovascular disease, VCID risk factors, aging, resilience, genetics, amyloid, tau, and neurodegeneration including along the life course.”

Reference: Barbiellini Amidei C, et al. Association between age at diabetes onset and subsequent risk of dementia. JAMA. 2021 Apr 27;325(16):1640-1649. doi: 10.1001/jama.2021.4001.