Objectives: There is a widespread consensus that diabetes impairs cognitive functioning. However, some recent findings have shown that many health conditions generally thought to be detrimental to cognitive functioning are in fact linked to pre-morbid cognitive ability, suggesting reverse causation. To better understand the causality in diabetes-cognition relationship, this study investigates the association of older-age diabetes with concurrent and childhood cognitive functioning.
Methods: Lothian Birth Cohort 1936 participants (N=1017) completed the same general cognitive ability test at ages 11 and 70 years. Scores were compared between those with and without diabetes at age 70. Diabetes status was based on self-reports and haemoglobin A1c levels.
Results: People with diabetes had lower mean cognitive ability scores at ages 11 and 70 when compared with those without diabetes. The effect size was roughly similar at both ages (Cohen's d≈0.32). When adjusted for age-11 cognitive ability, diabetes status was not associated with cognitive ability at age 70. The association between childhood cognitive ability and older-age diabetes was partly accounted for by body mass index and cholesterol level in older-age.
Conclusion: In this sample, diabetes was associated with poorer cognitive ability in old age but this was because of life-long lower cognitive ability in people with diabetes instead of diabetes impairing cognitive functioning.
Keywords: Cognition; Cognitive ability; Diabetes; HbA1c; Metabolism.