Memory Decline, Alzheimer's Risk Linked To Diabetes

Early Study Provides Clues

According to a study reported in the Archives of Neurology, diabetes may affect a person's cognitive abilities, and may increase the risk for developing Alzheimer's disease (AD).

The findings, from the Rush Alzheimer's Disease Center's Religious Orders Study, add to a developing body of research examining a possible link between diabetes and cognitive decline.

Diabetes is a serious chronic disease that can be managed through lifestyle changes and medication. Over 18 million US adults have diabetes, and another 41 million adults ages 40 to 74 have pre-diabetes.

Diabetes Associated With Other Diseases

The National Diabetes Education Program describes diabetes as a chronic disease in which the body does not produce or properly use insulin, a hormone that is needed to convert sugar, starches, and other food into energy. As a result, people with diabetes have higher than normal blood glucose (sugar) levels.

If left uncontrolled, diabetes causes serious complications, including heart disease, stroke, vision loss, kidney disease, nerve damage, and lower limb amputations.

The new study is among the first to examine how certain cognitive "systems" - memory for words and events, the speed of processing information, and the ability to recognize spatial patterns - may be affected selectively in people with diabetes.

The research was conducted by Dr. Zoe Arvanitakis, Dr. David Bennett, and colleagues at the Rush University Medical Center in Chicago and funded by National Institute on Aging (NIA) at the National Institutes of Health (NIH).

The AD Center at Rush is one of 30 across the US supported by the NIA to study and care for Alzheimer's patients.

"The research on a possible link between diabetes and increased risk of AD is intriguing, and this study gives us important additional insights," says Dr. Neil Buckholtz, head of the Dementias of Aging Branch in the NIA neurosciences program. "Further research, some currently underway, will tell us whether therapies for diabetes may in fact play a role in lowering risk of AD or cognitive decline."

Study Finds Diabetes, Alzheimer's Link

For an average of 5.5 years, the Rush scientists followed 824 Catholic nuns, priests, and brothers who are taking part in the Religious Orders Study.

The participants received detailed clinical evaluations annually, including neuropsychological testing of five cognitive "systems" commonly affected by aging, AD, and other dementias (a brain disorder that affects a person's ability to carry out daily activities).

The areas studied included episodic memory (memory of specific life events), semantic memory (general knowledge), working memory (ability to hold and mentally rearrange information), perceptual speed (the speed with which simple perceptual comparisons can be made, such as whether two strings of numbers are the same or different), and visuospatial ability (the ability to recognize spatial patterns).

Over the study period, 151 of the participants had a clinical diagnosis of AD, including 31 who had diabetes. The researchers found a 65 percent increase in the risk of developing AD among those with diabetes compared with people who did not have diabetes.

"We found that diabetes was related to decline in some cognitive systems but not in others," says Dr. Arvanitakis. "This study represents a continuation of our research on possible risk factors for Alzheimer's disease."

In measures of cognitive function, perceptual speed was associated with an increased rate of decline over time, by about 44 percent, when comparing the diabetes and non-diabetes groups.

In other areas of cognition, the rate of change over the time period of the study was no different in the two groups.

However, the researchers state that at the beginning of the study the cognitive function scores of people with diabetes were lower than those of people without diabetes.

Stroke-related changes in the brain were found in a previous study to be tied to a decline in perceptual speed. The researchers could not say whether the link between cognitive decline and diabetes appeared because of the changes in the brain associated with Alzheimer's disease or those of some other common age-related condition like stroke or other vascular complications.

Studies looking at pathological or brain imaging data would be needed to address these possibilities.

"Researchers have not yet found a cure for Alzheimer's disease, but if we can identify factors that influence one’s risk of developing Alzheimer's disease, this may allow us to make progress towards identifying factors that decrease the risk of Alzheimer's disease," Dr. Arvanitakis says.

Always consult your physician for more information.

Online Resources

American Diabetes Association

Centers for Disease Control and Prevention (CDC)

HealthierUS.Gov

National Diabetes Education Program

National Diabetes Information Clearinghouse

National Institute of Diabetes & Digestive & Kidney Diseases

National Institute of Neurological Disorders & Stroke

National Institutes of Health (NIH)

National Institute on Aging

National Library of Medicine

July 2004

Memory Decline, Alzheimer's Risk Linked To Diabetes

Diabetes Associated With Other Diseases

Study Finds Diabetes, Alzheimer's Link

Alzheimer's Disease Facts

Online Resources

Other Resources:

Find a St. John's Mercy Physician

Diabetes Services at St. John's Mercy

Diabetes Health Information

St. John's Mercy Classes and Programs

Alzheimer's Disease Facts

Experts estimate that up to 4 million US adults suffer from Alzheimer's disease (AD). The disease usually begins after age 60, and risk goes up with age.

While younger people also may get AD, it is much less common. About 3 percent of men and women ages 65 to 74 have AD, and nearly half of those age 85 and older may have the disease.

It is important to note, however, that AD is not a normal part of aging.

The most common form of dementia (a brain disorder that seriously affects a person's ability to carry out daily activities) is AD.

AD involves the parts of the brain that control thought, memory, and language.

Although scientists are learning more every day, currently they still do not know what causes AD, and there is no cure.

Scientists do not yet fully understand what causes AD.

The National Institute on Aging (NIA) states that there probably is not one single cause, but several factors that affect each person differently.

Age is the most important known risk factor for AD. The number of people with the disease doubles every five years beyond age 65.

Family history is another risk factor. Scientists believe that genetics may play a role in many AD cases. For example, familial AD, a rare form of AD that usually occurs between the ages of 30 and 60, is inherited.

The more common form of AD is known as late-onset. It occurs later in life, and no obvious inheritance pattern is seen.

However, several risk factor genes may interact with each other to cause the disease. The only risk factor gene identified so far for late-onset AD, is a gene that makes one form of a protein called apolipoprotein E (apoE).

Everyone has apoE, which helps carry cholesterol in the blood. It is likely that other genes also may increase the risk of AD or protect against AD, but they remain to be discovered.

The NIA is sponsoring the AD Genetics Initiative to recruit families with AD to learn more about risk factor genes.

Scientists still need to learn a lot more about what causes AD. In addition to genetics and apoE, they are studying education, diet, and environment to learn what role they might play in the development of this disease.

Scientists are finding increasing evidence that some of the risk factors for heart disease and stroke, such as high blood pressure, high cholesterol, and low levels of the vitamin folate, may predispose people to AD.

Evidence for physical, mental, and social activities as protective factors against AD is also increasing.

The NIA points out that AD begins slowly. At first, the only symptom may be mild forgetfulness. In this stage, people may have trouble remembering recent events, activities, or the names of familiar people or things.

They may not be able to solve simple math problems. Such difficulties may be a bother, but usually they are not serious enough to cause alarm.

However, as the disease goes on, symptoms are more easily noticed and become serious enough to cause people with AD or their family members to seek medical help.

For example, people in the middle stages of AD may forget how to do simple tasks, like brushing their teeth or combing their hair. They can no longer think clearly. They begin to have problems speaking, understanding, reading, or writing.

Later on, people with AD may become anxious or aggressive, or wander away from home. Eventually, patients need total care.

Always consult your physician for more information.