Marked Cognitive and Memory Decline in People Who Develop Diabetes in Mid-life
People who develop diabetes in middle-age are more likely to experience significant memory and cognitive problems over the next 20 years compared to people without diabetes in midlife, according to a prospective cohort study in the December 2 Annals of Internal Medicine.
“This research shows that to protect the brain in old age, we need to tackle cardiovascular risk factors in mid-life. Diabetes in mid-life is an important potentially modifiable risk factor for cognitive decline in old age,” said senior author Elizabeth Selvin, PhD, MPH, Associate Professor of Epidemiology and Medicine, Welch Center for Prevention, Epidemiology and Clinical Research and the Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
“We found that persons with diabetes or prediabetes had significantly faster cognitive decline as compared to persons with no diabetes at the beginning of the study,” Dr. Selvin said. “For example, on average, a 60-year-old with diabetes experiences cognitive decline on par with a healthy 65-year-old aging normally. Persons with diabetes with poor glucose control were at particularly high risk for cognitive decline,” Dr. Selvin explained.
Prospective Cohort Study Evaluated
Researchers studied data from 13,351 adults (24% black; 76% white) aged 48 to 67 years (mean age at baseline, 57 years) enrolled in the Atherosclerosis Risk in Communities Study (ARIC). The study followed patients from 1987 to 2013 in 4 communities in Maryland, North Carolina, Minnesota, and Mississippi.
The following 3 neuropsychological tests were used to assess cognitive function between 1990-1992 and again approximately 6 and 20 years later:
- Delayed word recall test (DWRT)
- Digit symbol substitution test (DSST) of the Wechsler Adult Intelligence Scale-Revised
- Word fluency test (WFT)
Scores on these tests were summarized with a global Z score.
Diagnosed Diabetes Linked To Greater Cognitive Decline
Participants with a history of diagnosed diabetes had significantly greater declines in scores on all cognitive function tests except the DWRT. The average decline in global cognitive Z score over 20 years was greater in persons with diabetes than in those without diabetes (0.92 vs 0.78; difference, -0.15 [95% CI, -0.22 to -0.08]), equating to a 19% greater decline among those with diabetes. The results were the same for both white and black participants.
Participants with poorly controlled diabetes (hemoglobin A1c [A1c] ≥7.0%) had the greatest decline in cognitive function scores, with a significantly greater decline compared with patients with controlled diabetes (A1c <7.0%; adjusted global Z-score difference, -0.16; P=0.071). Longer duration of diabetes also was associated with a significantly greater cognitive decline (P for trend <0.001).
Similarly, participants with prediabetes at baseline (ie, A1c 5.7%-6.4%) showed significantly greater cognitive decline compared with people without diabetes and an A1c <5.7% (adjusted difference in global cognitive Z score, -0.07; P=0.005)
“We know that even weight loss of 5% to 10% of body weight can be significant for prevention of diabetes. If we can prevent diabetes and [help achieve] better control glucose in persons with diabetes, we may be able to prevent or delay cognitive decline in old age,” Dr. Selvin said.
February 17, 2015