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Type 2 Diabetes Linked to Difficulties With Mental Tasks

From the WebMD Archives

Jan. 26, 2000 (Boston) -- Older women with type 2 diabetes are more likely to have problems with memory, concentration, and general mental tasks than nondiabetic women, according to CDC researchers.

Men were not included in the study, which was part of a larger overall study of the consequences of fractures in women with osteoporosis, but the findings would likely apply to them as well, the researchers tell WebMD.

In a six-year study of more than 9,500 women aged 65 and over, women with type 2 diabetes scored lower on three cognitive (mental-function) tests and had a greater rate of decline in mental function over 3-6 years than did women without diabetes.

The study also showed that women who had diabetes for 15 years or longer were most likely to have experienced a decline in abilities such as attention, language, and eye-hand coordination, write Edward W. Gregg, PhD, and colleagues. The results of the study appear in the Jan. 24 issue of the Archives of Internal Medicine.

"Our finding of an increased risk of cognitive decline associated with diabetes has important clinical, public health, and social ramifications. Cognitive impairment may be considered a potential long-term outcome of diabetes that clinicians should be aware of while taking care of older adults with diabetes," they write.

Earlier studies have led the researchers to expect some differences in mental function between diabetic and nondiabetic women. "What did come as something of a surprise, though, was that there's a 70% increased risk of a major decline on average, and that people who are taking insulin had a higher risk of cognitive decline. We don't think it was the insulin itself, but rather that insulin use was a marker of severity of disease," says Gregg, a researcher with the CDC's division of diabetes translation.

Gregg tells WebMD that although it is still unclear exactly how diabetes might affect mental processes, the best course of action for patients with type 2 diabetes may be to follow their doctors' advice and carefully control their blood sugar levels through the right combination of diet, exercise, medication, and, if necessary, insulin.

Although the study was not designed to determine how diabetes might affect the brain, the researchers were able to rule out some other factors that are often associated with aging or with diabetes, such as blood vessel narrowing that could lead to decreased blood flow to the brain or stroke, high blood pressure, or depression.

"From a research point of view, it makes us think about what is the link between diabetes and cognitive function," David A. Bennett, MD, tells WebMD.

Bennett, who wrote an editorial accompanying the study, is with the Rush Alzheimer's Disease Center and department of neurological sciences at Rush-Presbyterian-St. Luke's Medical Center in Chicago. "Why do people with diabetes lose cognitive abilities? The easiest explanation is that diabetes is associated with strokes, but on the other hand, that may not be true. It may actually be related to insulin metabolism and the way the brain deals with insulin and diabetes," he says.

Bennett says that because type 2 diabetes is caused by the body's increasing inability to use insulin to process glucose, the major form of sugar in the blood, the disease may somehow alter the ability of individual nerve cells in the brain to store and use glucose. Some brain researchers think that problems with glucose metabolism may cause or contribute to Alzheimer's disease or other forms of dementia.

The study was supported in part by grants from the Public Health Service of the National Institutes of Health.

Vital Information:

  • A new study shows that older women with type 2 diabetes are more likely to have problems with memory, concentration, and general mental tasks compared to nondiabetics.
  • Men were not included in the study, but researchers suspect the findings would apply to them as well.
  • Two possible explanations for the results are that the disease is associated with strokes, or that insulin metabolism is altered in the brain of diabetics