Earlier Age at Diabetes Onset Confers Greater Risk of Dementia Later in Life

Elizabeth Selvin, PhD, MPH
Credit: Johns Hopkins Medicine

The younger a person is at disease onset, the greater risk of developing dementia later in life for people with type 2 diabetes, according to a new study of more than 13,000 people.

An analysis of the Atherosclerosis Risk in Communities (ARIC) study, results suggest diagnosis of type 2 diabetes was associated with increased risk of dementia and this association increased in strength as age of onset decreased, with those diagnosed before 60 years of age at a nearly 3-fold increase in risk of dementia.

“Our study confirms the strong link between diabetes and dementia risk but we found strong modification of this association depending on the age of onset of diabetes,” wrote investigators. “Diabetes that was diagnosed earlier in adulthood (age <60 years) was strongly associated with dementia risk whereas old-age onset diabetes (age >80 years) did not contribute to an excess risk of dementia.”

The world of diabetes management has experienced an onslaught of advances in therapeutics, management, and research in recent decades. Among the plethora of new topics and discoveries has been the potential increase in risk of dementia associated with a diagnosis of diabetes. In 2021, a study leveraging data from the UK concluded earlier onset of diabetes was associated with increased risk of dementia. In the current study, Elizabeth Selvin, PhD, MPH, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, sought to examine associations between prediabetes and dementia among a cohort of patients in the US.

With this in mind, investigators designed the current study as an analysis of the ARIC study. The landmark ARIC study enrolled patients aged 45-64 years of age in 1987-1989 from counties in North Carolina, Mississippi, Minnesota, and Maryland. For the current study, the baseline period was visit 2 of the ARIC study, which occurred from 1990-1992 and was the first time HbA1c and cognitive function were measured as part of study protocol.

From the study, investigators obtained information related to 11,656 participants without diabetes at baseline and 2330 participants with prediabetes. The overall study cohort had a mean age of 56.8 (SD, 5.7) years and 55.3% were female. Investigators noted the portion of the cohort with prediabetes had a greater burden of lifestyle and clinical risk factors, were more likely to be Black, and more likely to have lower than a high school education.

For the purpose of analysis, investigators defined baseline predicates as an HbA1c of 5.7-6.4% and incident diabetes was defined as a self-reported physician diagnosis or use of diabetes medication. Investigators expressed a specific interest in examining associations of prediabetes with dementia risk both before and after accounting for development of diabetes.

Before adjusting for incident diabetes, results suggested prediabetes was significantly associated with increased risk of dementia (Hazard ratio [HR], 1.12 [95% CI, 1.01-1.24]; P < .05), but this increase in risk was attenuated and became nonsignificant (HR, 1.05 [95% CI, 0.94-1.16]). Analysis assessing the effect of age at onset of diabetes suggested earlier age was associated with increased risk, with those with disease onset before 60 years at the greatest risk of dementia followed by those with onset at 60-69 years (HR, 1.73 [95% CI, 1.47-2.04]) and those with onset at 70-79 years (HR, 1.23 [95% CI, 1.08-1.40]).

“Prediabetes is associated with dementia risk, but this risk is explained by the development of diabetes. Diabetes onset at early age is most strongly related to dementia. Thus, preventing or delaying the progression of prediabetes to diabetes will substantially reduce the future burden of dementia,” wrote investigators.