Losing the Protective Effect of Cognitive Aging in Mexican American Diabetics

Background: Diabetes is a serious health issue, affecting nearly 29 million people in the US. Mexican Americans (MA) have higher rates of diabetes, a risk factor for Alzheimer’s disease and mild cognitive impairment. Normal cognitive aging is associated with decline, not impairment, in some areas of cognition (processing speed, memory, etc). Diabetes may contribute to age associated cognitive decline and to the development of cognitive impairment. This study examines the effect of age on memory and executive functioning (EF) among diabetic and nondiabetic MA. Methods: Data from 415 MA subjects from the Health and Aging Brain among Latino Elders study (HABLE) were analyzed. Participants were classified as diabetic (n=171) or non-diabetic (n=244) and young (50 to 64, n=326) or old (65 and older, n=89). All participants were classified as normal controls (i.e., no diagnosis of dementia or MCI). Each participant underwent an interview (i.e., medical history and medications), cognitive testing, blood tests, and medical examination, as well as informant interviews. Memory was assessed by the Ravens Auditory Verbal Learning Test (RAVLT) Recognition and Delayed Recall, while EF was measured by Trail Making Test (TMT) Parts A&B and CLOX Part 1&2. Analyses were split by diabetes status (diabetic, non-diabetic) and age group (young, old), using independent t-tests. Results: Younger non-diabetic subjects scored significantly better than older non-diabetic subjects on measures of memory: RAVLT-Delayed Recall, t (3)=3.109, p=.002 , and executive functioning: TMT-A, t(56.450)=-3.529, p=.001, TMT-B, t(206)=-2.09, p=.004, and CLOX Part 2. Younger diabetic subjects scored significantly better than older diabetic subjects on measures of memory: RAVLT-Delayed Recall, t (109)=2.57, p=.012, and EF: TMT-A, t(44.177)=-2.257, p=.03, TMT-B, t(138)= -2.250, p=.026, and CLOX Part 2. Conclusion: It was expected that younger participants would perform better than older participants on all cognitive tests, regardless of diabetic status. However, the results indicated that younger and older diabetics demonstrated a similar pattern of performance on measures of memory and executive functioning, suggesting that younger age may no longer be a protective for diabetics. This study was limited by small sample size and cross sectional nature of the data. Further research is needed to understand the impact of health risks on normal cognitive aging.