Since the early 1900s, physicians have noted that people with both type 1 and type 2 diabetes often experience some degree of cognitive dysfunction—that is, problems relating to mental processes like learning, reasoning, and memory.
A new study in Annals of Internal Medicine found that diabetes in midlife is associated with a 19 percent greater cognitive decline over 20 years when compared with people who don’t have diabetes. The study also reports that diabetes ages the brain roughly five years. So, for example, a 60-year old with diabetes has the cognitive age of a 65-year old without.
"More severe levels of cognitive decline are also seen in patients with higher blood sugars," says Kathryn A. Boling, MD, a primary care provider at Lutherville Personal Physicians, which is affiliated with Mercy Medical Center in Baltimore.
In patients with type 1 diabetes, the most common cognitive shortcomings are decreases in the rate at which they can take in, evaluate, and act on new information (information processing speed) and the speed at which they move muscles in response to mental processes (psychomotor efficiency).
Type 2 diabetes patients are most likely to experience deficits in psychomotor efficiency and executive functioning, or complex cognitive processing. Examples of this include planning a trip or completing a project at work.
What the Study Shows
This study tracked more than 13,000 people for 20 years, measuring changes in participants’ cognitive skills in a standardized way. It included people with and without diabetes, and its rigorous methodology makes it a strong study. Boling says other studies have also shown an association between duration of diabetes and higher levels of cognitive decline.
Researchers don’t know precisely why there is a strong association between diabetes and cognitive decline, but it may be due to the link between diabetes and vascular (circulatory, or affecting the blood or lymph vessels) disease or the effect of raised blood sugar (glucose) levels.
So, how do you know if you have cognitive impairment?
"Patients will often come to the doctor with worries about their memory and this may be corroborated by a close relative," says Boling. "Sometimes the ability to perform certain tasks has become harder. If the patient describes a decline over time, this is also a hint that there may be cognitive decline."
If there are concerns, "Physicians can perform tests in the office, such as a mini-mental state exam (MMSE), a fairly quick test that can help identify cognitive decline," Boling explains. The MMSE includes questions about the patient’s location (address, city, and state); and time and date (day, month, and year); the patient may also be asked to memorize a short list of items, identify everyday objects, like a pencil, or follow simple instructions, such as repeating a phrase. "If there are questions regarding the accuracy of this exam, more intensive neuro-cognitive testing [assessments of thinking ability] can be performed."
But Boling says all is not lost if you’ve already begun experiencing cognitive decline: "Studies also show that keeping blood sugars under tight control not only decreases the risk of cognitive degeneration over time, but may also reverse some existing cognitive decline."
So in addition to managing blood sugar levels, exercising, and maintaining a healthy weight, you can take steps to help prevent, or slow, cognitive decline. Boling encourages patients to take the following steps:
- Don’t smoke.
- Avoid both diet and regular sodas.
- Control high cholesterol and blood pressure.
- Identify and treat depression.
- Nurture social relationships; Boling says connection with others decreases the risk of cognitive decline in general.
Kathryn A. Boling, MD, primary care provider at Lutherville Personal Physicians, reviewed this article.
Sources
Kathryn A. Boling, MD. Primary Care Provider at Lutherville Personal Physicians. Email to author. December 22, 2014.
Rawlings, Andreea M; A. Richey Sharrett, Andrea L.C. Schneider, Josef Coresh, Marilyn Albert, David Couper, Michael Griswold, Rebecca F. Gottesman, Lynne E. Wagenknecht, B. Gwen Windham, and Elizabeth Selvin. "Diabetes in Midlife and Cognitive Change Over 20 Years: A Cohort Study." Annals of Internal Medicine 2014 161(11): 785-793. doi:10.7326/M14-0737.
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