Analysis of data from the ARIC (Atherosclerosis Risk in Communities) study reveals that adults diagnosed with diabetes before the age of 60 years have an increased risk of developing dementia, while for those diagnosed at 80 years or older the risk was not increased.
Researchers collected data from participants enrolled at four sites in the US (mean age, 56.8 years; 55.3% women). Amongst 11,656 adults without diabetes at baseline (1990–1992), 2300 (20.0%) had prediabetes (defined as an HbA1c of 39–46 mmol/mol). Subsequent incident diabetes was defined by a formal diagnosis or use of antidiabetes medication. Incident dementia was determined via active surveillance. Follow-up continued until first diagnosis of dementia, death, loss to follow-up or the end of the study (2019).
During a median follow-up of 15.9 years, 3143 participants developed diabetes. More adults with prediabetes (44.6%) developed diabetes than those without prediabetes (22.5%).
Of the cohort, 2247 participants developed dementia during a median follow-up of 24.7 years. More adults with diabetes (23.9%) developed dementia than those without diabetes (20.5%).
Before accounting for incident diabetes and other covariates, prediabetes was significantly associated with the risk of dementia (HR, 1.12). After adjustment, however, the association was attenuated and non-significant (HR, 1.05).
Earlier age of onset of diabetes had the strongest association with dementia. Adults who were diagnosed with diabetes when ≤60 years had a higher risk for dementia than those without diabetes (aHR, 2.92), while the risks for those who developed it from 60 to 69 years (aHR, 1.73) and 70 to 79 years (aHR, 1.23) were also higher than for those without diabetes. There was no increased risk for dementia for those diagnosed at ≥80 years.
The researchers conclude that the association of prediabetes with dementia risk is explained by the subsequent development of diabetes. Preventing or delaying the progression of prediabetes to diabetes, especially in younger adults, is important in reducing the dementia burden. Modest weight loss through referral to initiatives such as the NHS Diabetes Prevention Program can be effective in achieving this goal.
The study results can be read in full here.