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Diabetes linked to cognitive impairment, life expectancy

Study results indicate that older adults with diabetes have a higher chance of cognitive impairment and a shorter life expectancy compared with those without.

“A recent estimate suggests that diabetes is associated with a 40% increase in the odds of dementia among older Americans. The precise physiologic pathways linking [diabetes and cognitive impairment] remain largely undetermined,” Carlos Díaz-Venegas, PhD, from the Max Planck Institute for Demographic Research in Rostock, Germany, and colleagues wrote in PLOS One. “Given that cognitive impairment is a major cause of loss of independence, presents a barrier to medication adherence and results in extremely high care costs, policies aimed at improving outcomes among those with diabetes should be informed by the level of cognitive impairment in this population.”

Using data from the U.S. Health and Retirement Study, researchers studied age at onset of cognitive impairment and life expectancy with and without cognitive impairment by diabetes status among middle- and older-aged adults. The total sample included 13,687 individuals aged 50 to 74 years who contributed 136,367 person-years of follow-up from 2000 to 2012. They interviewed participants via telephone to measure cognitive function.

After stratifying by gender and controlling for age, education and race/ethnicity, they estimated diabetes-status specific transition probabilities across six combinations (staying not impaired; staying impaired; impaired to not impaired; not impaired to impaired; not impaired to dead; impaired to dead). Then, they calculated age at onset of cognitive impairment and life expectancy with and without cognitive impairment by diabetes status at age 50 years.

The results show diabetes as a strong indicator of increased mortality and cognitive decline. For men, women and for most ages, those with diabetes had a higher prevalence of cognitive impairment than those without. The researchers found that the average cognition score for people with diabetes was 1.7 points lower and the prevalence of cognitive impairment was more than 10% higher compared with those without diabetes (25% vs. 14%; P .01).

From age 50 years, men and women with diabetes had a first incidence of cognitive impairment 3 and 4 years earlier, respectively, than those without diabetes. Diabetes decreased total life expectancy by 5 to 7 years and cognitively healthy life expectancy by 4 to 6 years. Compared with individuals without diabetes, those with diabetes lived approximately 1 year less with poor cognitive health. Furthermore, although education was strongly protective of cognitive health, diabetes was linked to lower age at cognitive impairment onset and fewer cognitive healthy years lived across all educational groups.

“The cost of diabetes on length of life is mostly due to reductions in years of cognitively normal functioning,” Díaz-Venegas and colleagues wrote. “Further study is needed to ascertain whether those with diabetes are also experiencing declines in cognitive impairment over time. If the welcome progress against mortality among the population with diabetes is not coupled with improved cognition, the cognition burden associated with diabetes may grow over time.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.