Prevention | Understanding complications
Diabetes Can Affect Cognitive Function
Cognitive decline is a less commonly known complication
In January 2000, the Archives of Internal Medicine published research involving 9,627 diabetic women aged 65 years and older and living in Maryland, Minnesota, Pennsylvania and Oregon. Researchers found that women with diabetes had lower baseline scores for cognitive function and experienced greater cognitive decline than did women without the disease. For women who'd had the disease for 15 years, diabetes was associated with a 57 percent to 114 percent greater risk of major cognitive decline. HopkinsHealth spoke with Christopher D. Saudek, M.D., professor of medicine and director of the Diabetes Center at Johns Hopkins, and Richard R. Rubin, Ph.D., associate professor of medicine and pediatrics at Johns Hopkins. Both men agree that diabetes patients and their doctors should pay attention to these cognitive issues.
HopkinsHealth (HH): What is meant by cognitive decline?
Dr. Saudek: These researchers measured the ability to carry out mental, or thinking, tasks. In this case, they used standard tests of mental functions. Dr. Rubin: Cognitive decline means a drop in a person's scores on standard tests of concentration, memory, attention and decision-making abilities. In this study, women with diabetes were much more likely to have a big enough drop in scores on some tests to affect day-to-day functioning.
HH: Could a decline in cognitive ability change whether a person could live alone, independently?
Dr. Saudek: Yes, but only if the decline is severe.
Dr. Rubin: I agree with Dr. Saudek, but I don't want people to think that any drop in mental capacity means a person can't live alone or do anything else they need to. We all have trouble with some aspects of cognitive function as we get older. My mother-in-law jokes that she has "Partzheimer's disease," because she forgets things part of the time. The real question is whether these declines in cognitive function compromise a person's ability to live well. This study suggests people with diabetes should pay special attention to these issues.
HH: Why do you think diabetes could cause this decline?
Dr. Saudek: I think that when it's not taken care of, diabetes is a strong risk factor for hardening of the arteries, or atherosclerosis. My presumption is that the generalized atherosclerotic process, which affects the brain, often causes these declines in mental functioning. In a sense, it's an accelerated aging process. But it would occur only if the diabetes and risk factors such as high blood pressure were not taken care of.
HH: Would controlling diabetes help?
Dr. Saudek: Yes. There's a big difference between people who take care of their diabetes and those who don't. Taking care of blood sugar is important. Smoking, blood pressure and other risk factors for atherosclerosis, however, can accelerate hardening of the arteries and can cause ministrokes. They can hardly be noticed, but they result in a loss of mental function. These strokes may be so tiny that people don't realize they're having them, but they affect tiny areas of the brain.
Dr. Rubin: This study looked at the duration of diabetes, too, and that's very important because if you're an average person diagnosed with diabetes, you've had it for some time before it is detected. The average person with adult-onset diabetes actually has it for seven years before it's diagnosed, and during that time, it's doing damage.
HH: What is the best way to prevent adult-onset diabetes?
Dr. Saudek: A recently completed National Institutes of Health study has shown that weight control can prevent diabetes in many people at risk for Type 2 diabetes. So one major way is to avoid being overweight, to keep your normal weight. Overweight people are at much higher risk of diabetes. Once people are overweight, intensive interventions designed to help them lose weight actually work to lessen the risk of diabetes. But as important as preventing diabetes is taking care of diabetes once it exists. You may be able to prevent it, but if you can't, you can manage it. You can't go along with the idea that you have "a touch of diabetes" and ignore it. This study shows the potentially detrimental effects of that kind of approach.
HH: So if people properly controlled their diabetes, they could avoid this cognitive decline?
Dr. Saudek: Yes, I expect they would. Now that's a guess on my part, but that would be my strong presumption. If the diabetes and associated risk factors were taken care of, that would avoid this kind of decline. From what we know, if you manage diabetes well, you can avoid its complications.
HH: This study looked at older women; do you think diabetes could cause the same cognitive problems in men?
Dr. Saudek: Yes, I would think so.
HH: Are patients and their doctors aware that cognitive decline is a complication of diabetes? I think most of us think of complications as having to have feet amputated or, perhaps, increased risk of heart attack.
Dr. Saudek: I think this information on cognitive decline is more subtle and less documented; it's not a commonly known or appreciated fact. That's why I was interested in this research, too. This is a new finding. It needs to be confirmed and it needs to be evaluated to see if the changes significantly affect a person's functioning.
HH: Anything else you'd like to add?
Dr. Saudek: These women would be predominantly Type 2 diabetics. There is often discussion on whether hypoglycemia can cause permanent changes in cognitive function. The changes seen in this study were not caused by insulin.
