What is the association between long-term glycemic control and developing dementia in adults with type 2 diabetes mellitus?
In this large population-based cohort, older adults with T2DM whose cumulative glycemic control was greater 9% were at increased risk of developing dementia. (LOE = 2b)
Overuse alert:This POEM aligns with the Canadian Geriatric Society’s Choosing Wisely Canada recommendation: Avoid using medications known to cause hypoglycemia to achieve hemoglobin A1c <7.5% in many adults age 65 and older; moderate control is generally better.
These researchers used a diabetes registry from Kaiser Permanente Northern California and identified 253,211 adults with type 2 diabetes (T2DM) who were at least 50 years of age, had at least 2 glycated hemoglobin (HbA1c) readings and at least 3 years of follow-up, and did not have dementia at baseline. The registry included pharmacy and laboratory information, hospitalization records, and outpatient diagnoses. The authors grouped the HbA1c values into 6 groups (< 6%; 6% to < 7%; 7% to < 8%; 8% to < 9%; 9% to < 10%; 10% or more). Among the cohort, the researchers had more than 4.6 million HbA1c measurements and a median 5.9 years of follow-up. Half the patients were White (50.6%), 9.9% were Black, 14.6% were Hispanic, and 17.5% were Asian. During the study time frame, 39,266 (15.5%) died and 21,139 (8.3%) received a diagnosis of dementia. After multiple adjustments for factors potentially related to developing dementia or to degrees of glycemic control, the authors found a J-shaped relationship between glycemic control and the risk of developing dementia. The patients with cumulative HbA1cs of 9 to < 9.9% and those with cumulative HbA1cs greater than 10% had the greatest adjusted risk of dementia (hazard ratios [HRs] 1.31 and 1.74, respectively). This study only shows associations, and many other factors the authors could not statistically manipulate could plausibly explain the association. To their credit, the authors state that their data support “relaxed glycemic targets for older people with type 2 diabetes.”
Henry C. Barry, MD, MS
Michigan State University
East Lansing, MI