Risk of cognitive decline doubles for older women
Dysfunction is speeded up by diabetes, says CDC
Older women with diabetes have as much as double the risk for declining cognitive functions than their nondiabetic counterparts, presenting "important clinical, public health, and societal ramifications," according to a Centers for Disease Control and Prevention (CDC) study published in the Jan. 24 issue of the Archives of Internal Medicine.
"This doesn’t mean it is time yet for large scale cognitive function screening of diabetic women in primary care," says Edward W. Gregg, PhD, an epidemiologist in the CDC’s Division of Diabetes Translation in Atlanta. "But it does reinforce the wisdom of talking to families of patients and discerning if there is cognitive decline."
Gregg joins the chorus calling for strict glycemic control. "We know better control can prevent other complications. It won’t hurt cognitive function, and it may actually help it."
In one of the largest studies of its kind, researchers also found that diabetic women over age 65 who have had diabetes for 15 years "had a 57% to 114% greater risk of major cognitive decline than women without diabetes," wrote the CDC team, headed by Gregg.
The CDC team followed 9,679 community-dwelling white women living in Baltimore, Minneapolis, Portland, OR, and Monongahela Valley, PA, for six years; 682 of them, or 7%, had diabetes at baseline.
All women were given three tests of cognitive function at intervals — baseline, three years, and six years — and the diabetic women scored significantly lower and showed faster cognitive decline than their counterparts.
Investigators used a modified version of the Mini-Mental State Examination, which is commonly used for screening, and the Digit Symbol and Trails B tests, which are more sensitive to small changes and measure attention and concentration, quick thinking, and problem-solving skills, Gregg explains.
The declines are usually small and barely noticeable, especially to a clinician who may see a patient only for a few minutes or even an hour a few times a year, says Gregg. Signs of impairment may include lagging reaction times, searching for the "right word," difficulty learning new information, short-term memory loss, and a general physical and mental slowdown.
This is not dementia
Experts are quick to point out that declining cognitive function is not dementia, although it may eventually lead to a variety of diseases such as Alzheimer’s. Alzheimer’s affects one-third of all women and 16% of all men over age 65. However, clinicians should not confuse declining cognitive function with Alzheimer’s or other forms of dementia, which typically involve emotional and behavioral components, Gregg cautions.
"There are a number of potential mechanisms at work here, and my best guess is that a combination of factors are at work, including microvascular effects exacerbated by diabetes," says Gregg. "We already know about small strokes and the effects of diabetes on the heart and cardiovascular system, and they are likely to be partly responsible for this kind of cognitive decline."
He adds that while the study was somewhat limited because all participants were white and female, the results do not appear to be connected to gender or race. "There is no reason to believe the same effects would not be seen in other populations."
Gregg says his findings should not be taken as a dismal sign for diabetic patients. "There is something you can do about it. Geriatric psychologists say there are things that can be done to prevent further cognitive decline. I think the answer for diabetic patients lies in better control. We know tighter control can prevent other complications, and it certainly won’t hurt cognitive function. It may actually help it."
Gregg suggests that a patient’s family probably has the best perception of gradual cognitive decline, so he recommends that clinicians spend some time with families and keep doors open for them to discuss areas of concern. Diabetes team members also might notice signs of cognitive impairment, which may warrant cognitive screening tests.
Diabetes is a difficult disease to manage, and cognitive decline may make that task overwhelming — and potentially destructive — for patients facing that slow downhill slide.
Gregg suggests that declining cognitive function may set up a downward spiral of worsening glycemic control. "If you have lousy control and subsequent loss of cognitive function, it cycles to worse control and more cognitive problems.
"Patients with declining cognitive function may have erratic eating habits and may have difficulty taking medications and getting the right dosages." He adds.
That makes a "solid support system" an essential tool for helping these patients, including family support and case management through primary care providers and diabetic support team attention.
Gregg’s findings get qualified support from David A. Bennett, MD, director of the Rush Alzheimer’s Disease Center at Rush-Presbyterian-St. Luke’s Hospital in Chicago.
In an editorial accompanying the publication of Gregg’s study, Bennett wrote that the CDC study has certain limitations of size, composition of the population group, and difficulty in general diagnosing cognitive dysfunction based on tests given at specific times.
He is also critical of the doctor-diagnosed diabetic population used in the study, since such a large of number of diabetics are undiagnosed.
"Cognitive decline is fundamentally a process of change in an individual’s performance over time," Bennett wrote. "Performance at a single point in time may bear little relation to subsequent changes in performance over time. Therefore, the ability to infer individual trajectories of change from a single observation is limited."
Bennett commends the study, however, as "well done, with good power, not a lot of bias with pretty unequivocal results."
He says the link between diabetes and cognitive decline is "Probably a true association that merits further study because we are always trying to identify the risk factors. I’m a little pessimistic about improving [cognitive function] rather than in preventing [decline]," says Bennett. "Prevention is a much more powerful tool."
He recommends that clinicians be very vigilant in terms of early detection and treatment of diabetes in older people. "Here’s one more negative outcome to add to the list of diabetes complications. If you’re in doubt whether or not to treat someone with impaired glucose tolerance, the addition of impaired cognition may help you tip the balance in favor of treatment."
He also suggests increased vigilance with new patients who tell you they’ve been diagnosed with diabetes. "This risk profile may change the way you think about things. For example, if someone comes to me with chest pain and he’s of normal weight, nondiabetic, and a nonsmoker, I might not place possible heart disease as high on my list of possible causes as I would in a patient who is diabetic, overweight, and a smoker."
"Knowing a patient has less cognition is not the kind of result that changes medical practice across the board. But it is something that we need to think about in practice and in future research," concludes Bennett.
[For more information, contact Edward Gregg at (770) 488-1263 and David Bennett at (312) 942-3350.]
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