Memory disorders such as Alzheimer’s disease (AD) are very common in older people. In fact, the likelihood of dementia in patients over 65 is about 13%, accounting for about one in eight persons over the age of 65. Diabetes, especially type II diabetes, is also a similarly common disease among the elderly and among patients with AD. According to the American Diabetes Association, over 18% of Americans over the age of 60 are affected by diabetes. Interestingly, these two conditions seem to have an impact on one another. Diabetes has been associated with changes in cognition, such as impaired learning and memory, slowed mental speed, and diminished mental flexibility. Moreover, patients with AD are more vulnerable to certain forms of diabetes.
The association between diabetes and AD appears quite strong amongst patients who carry the ApoE 4 allele, an inherited risk factor for the development of AD. The association between these two diseases is also strong in diabetic patients treated with insulin, a very common medication used to control blood sugar levels. In addition, loss of brain tissue itself, something also seen in patients with AD, seems to be more severe in elderly patients treated with insulin. There seems to be something about high levels of insulin that puts patients at risk for developing AD, as the “hyperinsulinemic state” typical of some forms of diabetes doubles the risk of AD. This is a condition that many diabetic patients experience when their own bodies produce too much insulin because their cells have become less responsive to normal levels of insulin. It has been shown that this “hyperinsulinemic state” may increase inflammation and affect the processing of molecules that lead to AD, potentially promoting memory impairment and AD. Interestingly, In addition, therapies that target this state show promise in improving cognition in patients with AD.
Other relationships between diabetes and memory loss, focusing more on demographic factors, have also been found. The Rancho Bernardo Study demonstrated a fourfold increase in cognitive decline in women with diabetes. This effect was not seen in men. In addition, improving control of blood sugar could actually ameliorate reduce this risk in women. In the California SALSA (Sacramento Area Latino Study on Aging) study patients of both sexes with diabetes were less likely to
develop cognitive and physical decline symptoms if they were taking diabetes medications. Despite the work that has been done so far, this area of research is still in its early stages.
The presence of memory loss and other cognitive impairments can interfere with almost every area of elderly patients’ medical care. This is especially so for individuals with diabetes, as patients with this condition must monitor their blood sugar levels, understand complex medication regimens, and adapt to complicated dietary changes and lifestyle modifications. In addition, patients’ rapidly changing treatment plans, many of them carrying the potential for dangerous adverse effects, further complicate the treatment management of patients with diabetes and concurrent cognitive deficits. Although researchers have begun clarifying the links between diabetes and AD, much is still not understood about how they may affect one another. Given the apparent associations between the two diseases, it is of particular interest to understand the molecular mechanisms underlying these interactions, as well as ways of preventing or ameliorating the effect of diabetes on memory. With an increasing percentage of America’s elderly population being affected by both diabetes and AD, better understanding of the possible relationship between these illnesses may have significant implications for the prevention and treatment of AD.