Background As the ageing population grows, it is important to identify strategies to moderate cognitive ageing.
Objective We examined glycated haemoglobin (HbA1c) and diabetes in relation to level and change in episodic memory in older adults with and without diabetes.
Methods Data from 4419 older adults with (n=950) and without (n=3469) diabetes participating in a nationally representative longitudinal panel study (the Health and Retirement Study) were examined. Average baseline age was 72.66 years and 58% were women. HbA1c was measured in 2006 and episodic memory was measured using immediate and delayed list recall over 4 biennial waves between 2006 and 2012. Growth curve models were used to assess trajectories of episodic memory change.
Results In growth curve models adjusted for age, sex, education, race, depressive symptoms and waist circumference, higher HbA1c levels and having diabetes were associated with poorer baseline episodic memory (p=0.036 and <0.001, respectively) and greater episodic memory decline (p=0.006 and 0.004, respectively). The effect of HbA1c on episodic memory decline was smaller than the effect of age. The results were stronger for women than men and were not modified by age or race. When the main analyses were estimated for those with and without diabetes separately, HbA1c was significantly linked to change in episodic memory only among those with diabetes.
Conclusions Higher HbA1c and diabetes were both associated with declines in episodic memory, with this relationship further exacerbated by having diabetes and elevated HbA1c. HbA1c appeared more important for episodic memory performance among women than men.
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Contributors CP planned the study, conducted the analyses and prepared the manuscript. RA planned the study, conducted the analyses and prepared the manuscript. FJI acquired the data, and prepared and edited the manuscript. SS prepared and edited the manuscript.
Funding The HRS is sponsored by the National Institute on Aging (grant number NIA U01AG009740) and is conducted by the University of Michigan.
Competing interests None declared.
Ethics approval University of Michigan and National Institute on Aging.
Provenance and peer review Not commissioned; externally peer reviewed.