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Diabetes during midlife increased cognitive decline in later years

Preventing diabetes and controlling glucose levels during midlife could protect against cognitive decline later in life, according to research published in the Annals of Internal Medicine.

“There is a substantial cognitive decline associated with diabetes, prediabetes and poor glucose control in people with diabetes,” Elizabeth Selvin, PhD, MPH, of Johns Hopkins Bloomberg School of Public Health, said in a press release. “We know how to prevent or delay the diabetes associated with this decline.”

Elizabeth Selvin

Selvin, with Andreea M. Rawlings, MS, also of Johns Hopkins, and colleagues used data from the community-based Atherosclerosis Risk in Communities (ARIC) study, believed to be the longest of its kind to follow a cross-section of adults as they age.

ARIC followed 15,792 middle-aged adults in communities in Maryland, North Carolina, Minnesota and Mississippi. Four visits occurred approximately 3 years apart, starting between 1987 and 1989, with a fifth visit between 2011 and 2013; cognitive function was evaluated at visits two, four and five.

After exclusions for lack of attendance, race, missing cognitive data and missing covariates, 13,351 white and black adults (mean age, 57 years; 56% female; 1,179 with diabetes) were included in the analysis.

Diabetes was defined by self-reported physician diagnosis, medication use or HbA1c ≥6.5%. Undiagnosed diabetes, prediabetes and glucose control in patients with diagnosed diabetes were defined by clinical categories of HbA1c levels.

The researchers used delayed word recall, digit symbol substitution and word fluency tests to assess cognitive performance; results were summarized with a global z score. Decline in word recall, memory and executive function are strongly associated with progression to dementia, according to the release.

Having 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) vs. no diabetes. Cognitive decline was higher among individuals with prediabetes (HbA1c 5.7%-6.4%) than those with HbA1c <5.7%.

Patients with poorly controlled diabetes (HbA1c ≥7%) showed a bigger decline than those who had their condition under control (adjusted global z score difference, –0.16; P=.071).

Patients with longer-duration diabetes demonstrated greater cognitive decline later in life (P for trend <.001); rates of decline did not differ significantly between whites and blacks (P for interaction=.44).

“If we can do a better job at preventing diabetes and controlling diabetes, we can prevent the progression to dementia for many people,” Selvin said in the release. “Even delaying dementia by a few years could have a huge impact on the population, from quality of life to health care costs.”

Disclosure: ARIC was a collaborative study supported by contracts with the National Heart, Lung, and Blood Institute, NIH; neurocognitive data collection was supported by NHLBI grants; and the research also was supported by the National Institute on Aging and NIDDK.