August 2015 Issue

Dynamics of Diabetes: Diabetes and Cognitive Decline
By Constance Brown-Riggs, MSEd, RD, CDE, CDN
Today's Dietitian
Vol. 17 No. 8 P. 18

Evidence suggests that good blood glucose control in middle age could preserve brain health later in life.

It's estimated that by 2050 there will be more than 83 million people aged 65 and older.1 And as this aging population continues to grow, there will be more cases of type 2 diabetes. The Centers for Disease Control and Prevention projects that the number of older individuals with diabetes will double or even triple by 2050, affecting one in three adults over the age of 65.2 Compared with older adults without diabetes, older people with type 2 diabetes show a 1.5- to two-fold increased risk of cognitive decline.3 Recent evidence shows an association between diabetes control in midlife and cognitive function in older age.

This article will discuss the correlation between blood glucose levels and cognitive decline and what dietitians can do to help clients and patients preserve their cognitive health through lifestyle changes and nutrition intervention.

What Is Cognitive Decline?
Impairments in cognitive function are common with advancing age and can range from mild cognitive impairment (MCI) to the more serious decline of dementia.4 Problems with memory, language, thinking, and judgment, beyond common age-related changes, are characterized as MCI. Cognitive decline is a precursor to dementia, a loss of mental capacity severe enough to interfere with a person's daily functioning. Alzheimer's disease and other neurological conditions can cause dementia,4 and diabetes is an independent risk factor for dementia.5

Examining the Link
It's well established in the literature that uncontrolled blood glucose in diabetes is a risk factor for microvascular diseases such as nephropathy and retinopathy.6 "We know that diabetes can cause damage to the small [blood] vessels in the body," says Elizabeth Selvin, PhD, MPH, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. "High glucose levels cause damage to the small [blood] vessels, making the vessel walls weaker and less flexible. In the eye and kidney, holes can form, and the capillaries can leak."

The literature also provides evidence that the risk of these diseases can be reduced with good blood glucose control.6 So could there also be a vascular basis for cognitive decline in elder individuals with diabetes? Selvin thinks it's possible. "We know less about what's going on in the brain, but it's possible that elevated glucose levels are causing damage to the small blood vessels in the brain," she says.

Previous randomized clinical trials conducted in the elderly and in people with long duration of diabetes have failed to show a correlation between glucose control and cognitive decline due to the shorter lengths of time researchers spent studying participants. "It's only by studying people for 20 years that we can truly understand how risk factors in midlife may contribute to health problems in old age."

In a study published in the December 2014 issue of the Annals of Internal Medicine, Selvin and colleagues examined the association between diabetes control in midlife with subsequent 20-year cognitive decline. For the study, researchers used data from the Atherosclerosis Risk in Communities Study (ARIC), which began following a group of 15,792 middle-aged adults in 1987. Participants were seen at four visits approximately three years apart beginning between 1987 and 1989, and were seen a fifth time between 2011 and 2013. Cognitive function was evaluated at visits two (1990 to 1992), four (1996 to 1998), and five.

The researchers compared the average amount of cognitive decline in the study participants with the amount of decline found in the ARIC participants. They determined there was a 19% increase in cognitive decline in subjects with poorly controlled diabetes. "The full underlying biology is still unclear, but this study adds to the growing evidence for a vascular basis for cognitive decline and dementia," Selvin says.

Impact of Cognitive Decline on Diabetes Self-Management
Selvin and colleagues also found that diabetes appears to age the mind about five years faster than the normal effects of aging. For example, on average, a 60-year-old with diabetes will experience the same amount of cognitive decline as a healthy 65-year-old who's aging normally. Loss of memory, word recall, and executive function are strongly associated with progression to dementia.

These symptoms become problematic when people with diabetes try to take care of themselves, since diabetes self-management requires a moderately high level of cognitive function. Every day a patient with diabetes must make healthful food choices in the right amounts and at the right time, take medication as prescribed, monitor blood glucose levels, and solve problems. Older individuals with diabetes and cognitive decline may not be able to follow complicated treatment regimens requiring multiple daily insulin injections, multiple oral medications, or complex dietary regimens.5 In fact, people with low cognitive function are more likely to have difficulty and require assistance in performing these self-care tasks.7

Certified diabetes educators (CDEs) routinely monitor lipids and renal function, and perform eye and foot exams. But they also should monitor patients' cognitive function and their ability to perform self-care behaviors. CDEs may need to adjust glycemic goals and simplify treatment regimens to prevent hypoglycemia. And they should consider the risk vs benefit of good blood glucose control.5

Counseling Patients
While it's important to monitor the overall health of older patients with diabetes, dietitians should help middle-aged individuals with diabetes understand that blood sugar control during this stage of life may help protect against cognitive decline as they grow older.

Ruth Frechman, MA, RDN, CPT, owner of the nutrition consulting business On the Weigh in Burbank, California, and author of The Food Is My Friend Diet, suggests the following tips to help patients preserve cognition:

• Check blood levels of folate, vitamin B6, and vitamin B12 periodically. A study published in the January 2007 issue of the American Journal of Clinical Nutrition associated normal vitamin B12 and folate levels with protecting cognition. Long-term use of Metformin, a common diabetes drug, may cause a vitamin B12 and folate deficiency.

• Encourage more fatty fish intake and use of turmeric in cooking. Diabetes is an inflammatory condition, and eating anti-inflammatory foods, such as turmeric and fatty fish (eg, salmon, tuna, trout) may have positive effects on brain health.

• Manage the impact of vascular complications. Control blood sugar, keep blood cholesterol and blood pressure within normal limits, achieve a healthy weight by following a healthful diet, and encourage smoking cessation.

As the population ages and more elderly people live with diabetes, the importance of good blood glucose control can't be overemphasized. "[Moreover], if we can prevent diabetes and better control glucose in middle-aged people with diabetes, we may be able to prevent or delay cognitive decline in old age," Selvin says.

— Constance Brown-Riggs, MSEd, RD, CDE, CDN, is a past national spokesperson for the Academy of Nutrition and Dietetics, specializing in African American nutrition, and author of The African American Guide to Living Well With Diabetes and Eating Soulfully and Healthfully With Diabetes.

1. U.S. Census Bureau. An aging nation: the older population in the United States. Published May 2014. Accessed June 17, 2015.

2. Number of Americans with diabetes projected to double or triple by 2050. Centers for Disease Control and Prevention website. Updated October 22, 2010. Accessed June 17, 2015.

3. The National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes Complications. Accessed May 8, 2015.

4. Mild cognitive impairment. Mayo Clinic website. Accessed May 8, 2015.

5. Munshi M, Grande L, Hayes M, et al. Cognitive dysfunction is associated with poor diabetes control in older adults. Diabetes Care. 2006;29(8):1794-1799.

6. Guiding principles for the care of people with or at risk for diabetes. National Diabetes Education Program website. Accessed March 26, 2015.

7. American Association of Diabetes Educators. The American Association of Diabetes Educators position statement: self-monitoring of blood glucose.
. Published May 2010. Accessed May 31, 2015.