Is Alzheimer’s disease in our blood?
By Richard. Filed in Random |Tags: alzheimers
With the number of people suffering from Alzheimer's disease on the rise, there is an urgent need to identify what causes this neurodegenerative illness. Your genes and your social and physical environment all play a role in determining how your brain will age, but which genes and which environmental factors are key?
A researcher trying to identify the cause of a disease is much like a detective trying to identify a criminal in a city full of suspects. Alzheimer's researchers around the world are currently studying a huge number of potential risk factors. Dr. Danielle Laurin, a Canadian Institutes of Health Research (CIHR)-supported scientist at Laval University, is trying to determine if exposure to chemicals such as PCBs and DDT could be the culprit.
"We know that these chemicals kill brain cells," says Laurin. "Also, there is evidence that when infants have diets high in organochlorines, it affects their mental development."
The effort to determine the causes of Alzheimer's is complicated for several reasons. First of all, Alzheimer's is a disease of old age, which means that many people who would eventually develop the disease die before they begin to experience symptoms. Also, Alzheimer's can take anywhere from five to twenty years to progress, so the onset of illness can vary widely from patient to patient. And, a definitive Alzheimer's diagnosis can only be obtained after a patient has died. These complications make it difficult for researchers to identify similarities between Alzheimer's patients that could reveal the roots of the disease.
"It is amazing the number of risk factors that have been investigated, and yet we've never really been able to pinpoint any risks other than education level, advancing age, and the presence of a specific version of a gene called apolipoprotein E," says Laurin.
But Laurin may be about to make a major break in the case. Early in her career, Laurin had an adviser who worked on a landmark project known as the Canadian Study of Health and Aging. This study tracked the health of more than 10,000 Canadians aged 65 and older over 10 years (1991 to 2001). Eighteen research centres across the country collaborated on the project.
"For a researcher, this study was a dream come true," explains Laurin. "There are very few long-term studies of this kind, because they are very expensive to conduct and difficult to coordinate."
Laurin is testing blood samples collected from 2,022 of the participants in the study to see if patients diagnosed with Alzheimer's and other forms of dementia had higher levels of organochlorines in their systems compared to those not affected by the disease. Organochlorines belong to a class of chemicals that includes the pesticide DDT and industrial by-products known as PCBs. Although these chemicals are strictly regulated in Canada, they are very long-lasting, so they are still present in our bodies and our environment. Because organochlorines stick around for so long, Laurin will be able to determine the study participants' level of exposure, even if that exposure happened years ago.
The results of Laurin's research could help narrow the field of suspects in the ongoing investigation on Alzheimer's disease. A better understanding of the role that organochlorines play in the progression of the disease could lead to improved screening and diagnosis and greater insight into how the disease works.
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