More than 500,000 Canadians live with dementia and, according to the Public Health Agency of Canada, another 75,000 are joining their ranks every year.
People suffering from dementia gradually lose their ability to think, remember, make decisions, converse and look after themselves. As the disease progresses, the brain changes and particular areas shrink as neurons die.
Alzheimer’s disease accounts for 50 to 75 per cent of dementia cases. No cure is known. The therapies that exist seek to slow cognitive decline rather than reverse it.
Scientists are not even absolutely sure what causes Alzheimer’s. Genetics plays a role, but so do environment, lifestyle and other illnesses.
New technologies promise to allow researchers to determine in the coming years what triggers the processes that lead to neuron death in Alzheimer’s patients.
In the meantime, growing evidence suggests Alzheimer’s might share close ties to Type 2 diabetes. Research has found strong links between insulin resistance, which leads to Type 2 diabetes, and memory decline and increased risk for Alzheimer’s disease.
Insulin, a hormone made by the pancreas, helps the body to use sugar in food for energy. When cells lose sensitivity to insulin, they become less able to metabolize glucose from the bloodstream. Type 2 diabetes ensues.
Impaired insulin sensitivity is linked to degenerative processes in the brain in both Type 2 diabetes and Alzheimer’s patients. Insulin resistance has also been observed in brains of Alzheimer’s patients.
In a circular risk pathway, Type 2 diabetes is a risk factor not just for Alzheimer’s disease but for cardio-vascular disease, which is itself a risk factor for Alzheimer’s disease.
Strengthening the diabetes-Alzheimer’s link is research into levels of an enzyme found in the fluid around the brain and spine. Scientists in Italy recently determined that higher levels of the enzyme autotaxin predict memory impairment and Type 2 diabetes in a person.
Just a one-point increase in autotaxin levels — for example, going from a level of two to a three — equals 3.5- to five-fold increased risk for being diagnosed with some form of memory loss and a 300 per cent increased risk of having Type 2 diabetes or pre-diabetes.
Also this past year, researchers from the U.K. announced that a drug developed for diabetes significantly reversed memory loss in mice bred to develop Alzheimer’s disease. The drug combines three growth factors — molecules that stimulate or “signal” cells to grow, divide and heal. Insulin is a growth factor, but not one of the three included in the drug.
Growth-factor signalling has been shown to be impaired in the brains of Alzheimer’s patients. Although the benefits of the drug have been seen only in mice to date, other studies with diabetes drugs have shown promise for people with Alzheimer’s.
Other research is looking into how a key therapy for preventing and managing diabetes and keeping the heart healthy — exercise — might help people at risk for developing dementia or Alzheimer’s disease.
• An Australian-U.K. study shows regular aerobic exercise can improve memory function and maintain brain health as we age. Regular aerobic exercise slowed loss of neurons, particularly in areas of the brain critical for memory formation.
• Canadian scientists found that as little as six weeks of intense exercise can lead to significant memory improvements, particularly complex memory recall. Study participants who saw greater fitness gains also saw greater gains in a protein that supports the growth, function and survival of brain cells.
• A U.S. study found that people at risk for Alzheimer’s disease who exercise at moderate intensities regularly tend to have better glucose metabolism in their brains. Moderately intense exercise — such as a brisk walk — was associated with healthier brain-glucose metabolism. Furthermore, participants who spent at least 68 minutes each day exercising at medium intensity had better glucose metabolism than participants who exercised less or at lower intensities.
Of course, much more research and time are needed before definitive results are known. But even if regular exercise doesn’t overcome the triggers that precipitate Alzheimer’s disease in a person, it might provide a buffer that delays onset or slows decline — and thus increase and extend quality of life.
What is good for the heart and the metabolism seems also to be good for the brain.
