Diabetes can double risk for Alzheimer’s

It has long been known that people with diabetes face an increased risk of serious health problems such as heart attack or stroke. Now a new study from Japan says that diabetes can also dramatically increase risk for Alzheimer’s disease and other kinds of dementia later in life.

For the study, published in the journal Neurology, researchers followed more than 1,000 men and women over age 60 for a period of 15 years. All were dementia-free at the start of the study.

The researchers, led by Yutaka Kiyohara of Kyushu University, also determined the participants’ diabetes status by using an oral glucose-tolerance test. When the study began, 15 per cent of the participants were diagnosed with diabetes and 23 per cent with pre-diabetes.

After following the participants for 15 years, researchers found that those with diabetes were twice as likely as the other study participants to develop Alzheimer’s disease. They were also 1.75 times more likely to develop other types of dementia.

The diabetes-dementia link

More study is needed to understand why diabetes may contribute to dementia, researches say. There, are, however a number of theories that could explain the link, according to Health.com:

— Insulin resistance, which causes high blood sugar and in some cases leads to type 2 diabetes, may also interfere with the body’s ability to break down amyloid, a protein that forms brain plaques that have been linked to Alzheimer’s. High blood sugar, or glucose, also produces oxygen-containing molecules that can damage cells in a process known as oxidative stress.

— Along with high cholesterol, high blood sugar can lead to the hardening and narrowing of arteries in the brain. This condition, known as atherosclerosis, can lead to vascular dementia, which occurs when artery blockages (including strokes) destroy brain tissue.

Researchers are hopeful that better understanding of the connection between diabetes and dementia could eventually lead to new treatments for Alzheimer’s disease. Prior research, for example, has indicated that the same drug — insulin — that treats diabetes may also help stave off the symptoms of cognitive decline for people with Alzheimer’s.

The findings also underscore, experts say, the importance of leading a healthy lifestyle to help prevent diabetes (such as eating a healthy diet, keeping physically active, and maintaining a normal body weight), and for people with diabetes or pre-diabetes, to take steps to control their blood sugar levels. (For more, see Put diabetes on hold.)

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Worldwide incidence of diabetes

According to the World Health Organization (WHO), about 346 million people worldwide have diabetes. In 2004, an estimated 3.4 million people died from consequences of high blood sugar, with 80 per cent of these deaths occurring in low-and middle-income countries. WHO projects that deaths resulting from diabetes will double between 2005 and 2030.

Worldwide incidence of Alzheimer’s disease

In 2010, there were an estimated 35.6 million people with dementia worldwide, according to Alzheimer’s Disease International. By 2050, it is projected that this figure will have increased to over 115 million. 1 in 11 Canadians over the age of 65 currently has Alzheimer’s disease or a related dementia, according to the Alzheimer Society.

Sources: Neurology; Health.com; WebMD; World Health Organization; Alzheimer Society; Time Magazine

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