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Decline in Cognitive Function As Key Factor in Life Expectancy for Person with Diabetes

Feb 24, 2018

Diabetes-status in older Americans can lead experts in establishing an association between cognitive impairment and mortality.

Diabetes has been shown to reduce life expectancy by approximately 10 years. Studies have shown an association between this endocrine disorder and a 40% increased risk of dementia in the elderly population. It is hypothesized that certain physiologic events are responsible for this association. These events include neuronal glucose processing, cerebrovascular complications and recurrent hypoglycemia. It is also known that people with diabetes tend to have comorbid cardiovascular complications. That in itself demonstrates its association to cognitive impairment due to cerebrovascular incidents.  Current studies on diabetes and cognitive impairment lack information about the onset of the cognitive decline and its link to life expectancy in these patients. This study aimed to look at all three topics and their relation to one another.

Carlos Díaz-Venegas et al. looked at the U.S. Health and Retirement Study (HRS) (2000-2012), a longitudinal study of Americans 50-74 years of age with high quality indicators of cognitive functioning. The total sample size was 13,687. Attrition was an issue when reviewing the Health and Retirement Study, as with most longitudinal studies, individuals were lost to follow-ups or have passed away. Their goals were to study the diabetes status of this population and the age of onset of the cognitive decline in relation to life expectancy beyond 50 years of age. Diabetes status was assessed by asking the question “have you ever been diagnosed with diabetes” at interview.  Cognitive function was measured based on responses to a revised version of the Telephone Interview for Cognitive Status (TICS-M) test. Scores ranged from 0-27 points, with 11 points or less defining cognitive impairment. Using multinomial regression models, the team analyzed data stratified by two socioeconomic factors: sex and education, due to the clear link between the risk of developing diabetes and cognitive impairment. They also looked at the life expectancy in this population without cognitive impairment using the Markov chain matrix population model. It was hypothesized that individuals with a higher educational level may practice healthier lifestyles and have better access to quality health care, which may reduce the negative cognitive complications of diabetes.

Characteristic results of the population showed that the prevalence of diabetes in the sample size was 14%, the mean age was 65 years of age and the majority of the samples size were women (57%). The majority of the selected population (76%) were white. Only one-fifth of the population were college graduates. Based on results of the TICS-M test, the mean cognition score was 16 points and 15% of the population fell into the cognitively impaired category. 30% of the population transitioned between cognitive states, while 4,247 individuals passed away. Diabetes status showed significant differences. Individuals with diabetes were more likely to be non-Hispanic black (23% vs. 12%; p£0.01) and had less than a high school degree (36% vs 22%; p£0.01). The reported cognitive test score in people with diabetes was 1.7 points lower. The prevalence of cognitive impairment was higher in those with diabetes than without (25% vs 14%; p£0.01) and more pronounced in women. Overall, the mean age for onset of cognitive impairment was 69.7 years, occurring earlier in men (68.5 years) than in women (70.5 years). Those without diabetes displayed a mean age of onset 3.7 years later (70.4 years) than those with diabetes (66.7 years), with men declining earlier than women. It is important to note that life expectancy did not match the age at first onset of cognitive impairment because of two reasons: (1) it is a transient state; (2) mean age at first onset is used only for those with cognitive impairment, while life expectancy measured everyone studied. Overall, the mean life expectancy remaining beyond 50 years old was 30.3 years (27.6 for men, 32.1 for women). Individuals without diabetes lived ~ one year longer with ~ 80-85% of that year cognitively healthy. Those with diabetes lived considerably less years with or without cognitive impairment in comparison to those without diabetes (men: 5.1 less, women: 7.3 less). The death rate was ~25% higher in individuals with diabetes in comparison to those without diabetes (3.7% vs 2.9%;p£0.01).

In conclusion, this study showed that diabetes is a strong indicator of early onset cognitive decline and mortality. Having diabetes by 50 years of age can shorten your lifespan, cognitively impaired or non-impaired. It is important to note that >80% is typically spent in a healthy, non-impaired cognitive state. Although diabetes does have a strong association between cognitive impairment and life-expectancy, those without diabetes were reported to have only one year less of impairment. This is because those with diabetes died before reaching the advance ages associated to dementia. Lastly, the differences in cognitively impaired life-expectancy became more narrow for when reviewing educational accomplishments showing an inverse relationship, validating the hypothesis.

Practice Pearls:

  • Diabetes may result in a decline of cognitive function, which can shorten one’s life expectancy.
  • Socioeconomic status plays a role in prevention of diabetes, cognitive impairment, and living a long and health life.
  • Men tend to regress mentally earlier in life than women.


Díaz-Venegas, Carlos, et al. “Life Expectancy With and Without Cognitive Impairment by Diabetes Status Among Older Americans.” Plos One, vol. 12, no. 12, 29 Dec. 2017, pp. 1-13., doi:10.1371/journal.pone.0190488.

Adrianna Jackson, Doctor of Pharmacy Candidate: Class of 2018; LECOM College of Pharmacy