BY SAM BAKER
Researchers have found people diagnosed with diabetes in their 50s are significantly more likely than others to suffer mental decline by their 70s.
In this week’s Vital Signs, Dr. Angela Bentle, a geriatrics and internal medicine specialist with Methodist Charlton Medical Center, explains why this seems to occur in middle age than with younger people.
Why this affects people in their 50s rather than younger: I think it’s a progression of a process that’s been going on in the diabetic patient. You have deterioration of kidney function, you have loss of vision in advanced cases. You have damage to the nerves in the feet, which causes ulcers and, sometimes, amputations. So it stands to reason if there’s nerve damage in other areas, that there would nerve damage or central nervous system damage, whether it’s through vasculature or the nerve cells themselves in the brain, and I think that’s a toxic effect of prolonged elevated blood sugar.
How does diabetes affect memory loss? I think that, just like in other organs – the kidneys, the nervous system, the eyes, that it’s a toxic effect. You know elevated blood sugar with a lack of insulin or insulin resistance, the blood sugar isn’t getting where it needs to be to do what it needs to do, all of your cells need glucose, but the insulin or the defective insulin isn’t help the blood sugar to get there to be utilized. And it causes damage by floating around in the system. Elevated sugar in the bloodstream is toxic wherever it is, and it seems to affect other end organs, so why not the brain? It stands to reason that the brain will be affected. And yes for at least ten to 20 years, it’s been noted that there is dementia or cognitive decline associated with the prolonged diabetes.
Are there symptoms to watch out for? Drinking more, going to the bathroom more, and being fatigued all of the time, and you can’t explain why that is, because diabetes persists - especially Type 2, for a number of years before its diagnosed, unlike Type 1, where there’s an absolute deficiency or the body’s not making the insulin. With Type 2, it’s a slower process.
Can memory loss, after it’s been detected and tied to diabetes, be treated? Once it’s there, there’s non-reversible memory loss. And if it’s coming from the prolonged toxic effects of diabetes, it’s unlikely that you can reverse the damage that’s been done. But you can slow that progression by controlling the blood sugar.
Diabetes in Midlife and Cognitive Change Over 20 Years: A Cohort StudyDiabetes in Midlife and Cognitive Change Over 20 Years
Andreea M. Rawlings, MS; A. Richey Sharrett, MD, DrPH; Andrea L.C. Schneider, PhD; Josef Coresh, MD, PhD, MHS; Marilyn Albert, PhD; David Couper, PhD, MS; Michael Griswold, PhD; Rebecca F. Gottesman, MD, PhD; Lynne E. Wagenknecht, Dr PH, MPH; B. Gwen Windham, MD; and Elizabeth Selvin, PhD, MPH
Background: Type 2 diabetes is associated with dementia risk, but evidence is limited for possible associations of diabetes and prediabetes with cognitive decline.
Objective: To determine whether diabetes in midlife is associated with 20-year cognitive decline and to characterize long-term cognitive decline across clinical categories of hemoglobin A1c (HbA1c) levels.
Design: Prospective cohort study.
Setting: The community-based ARIC (Atherosclerosis Risk in Communities) study.
Participants: 13 351 black and white adults aged 48 to 67 years at baseline (1990 to 1992).
Measurements: Diabetes was defined by self-reported physician diagnosis or medication use or HbA1c level of 6.5% or greater. Undiagnosed diabetes, prediabetes, and glucose control in persons with diagnosed diabetes were defined by clinical categories of HbA1c level. Delayed word recall, digit symbol substitution, and word fluency tests were used to assess cognitive performance and were summarized with a global Z score.
Results: Diabetes in midlife was associated with a 19% greater cognitive decline over 20 years (adjusted global Z-score difference, −0.15 [;95% CI, −0.22 to −0.08];) compared with no diabetes. Cognitive decline was significantly greater among persons with prediabetes (HbA1c level of 5.7% to 6.4%) than among those with an HbA1c level less than 5.7%. Participants with poorly controlled diabetes (HbA1c level ≥7.0%) had greater decline than those whose diabetes was controlled (adjusted global Z-score difference, −0.16; P = 0.071). Longer-duration diabetes was also associated with greater late-life cognitive decline (P for trend < 0.001). Rates of decline did not differ significantly between white and black persons (P for interaction = 0.44).
Limitation: Single HbA1c measurement at baseline, 1 test per cognitive domain, and potential geographic confounding of race comparisons.
Conclusion: Diabetes prevention and glucose control in midlife may protect against late-life cognitive decline.