Genetic testing for hereditary diseases is a somewhat controversial technology, developed in the past few decades, which can allow people to ultimately predict their future. For diseases such as Alzheimer’s and Huntington’s this can either be a blessing or a curse.
Huntington’s testing has existed for a few years, as the genetic market for the disease was discovered in the early 1990s and a test for it became commercially available a few years later. This test provides distinct benefits, such as preventing the gene from passing to future generations, and otherwise allowing time for the patient to organise their affairs. However, it also can be a hard idea to come to terms with if the test is positive. People with Huntington’s are four times more likely to commit suicide than the general population.
Alzheimer’s is another disease that has been a recent focus of genetic testing. Dementia affects around 35 million people worldwide, and this figure is likely to triple by 2050. The most common cause of dementia is Alzheimer’s Disease, alongside other types of dementia caused a number of small strokes or irregularities in brain cells. Roughly one in six people over 65 will be diagnosed with Alzheimer’s.
A study by Howard Federoff from Georgetown University, Washington DC, led to the development of the first blood test capable of predicting Alzheimer’s. This tests for ten chemicals, mostly lipids, present in fewer numbers in those with mild cognitive impairment; people who would proceed to get Alzheimer’s. Federoff and his team studied 525 patients that were 70 or older for 5 years, taking blood tests and performing neurological examinations. At the end of the third year, 202 patients remained in the study, of which 53 patients had a mild cognitive impairment or Alzheimer’s and 96 were healthy. The other 53 did not match criteria for either group and so were excluded from the biomarker profiling, which would determine the chemical markers for Alzheimer’s.
Once the ten chemicals had been determined, their functions were investigated and scientists discovered that they help to support cell membranes. A deficiency in these chemicals leads to a decrease in the number of neurons in the brain, potentially triggering Alzheimer’s. The depletion of these chemicals and thus lesser support for the cell membranes can be identified 10-20 years before the onset of the disease, allowing people to predict it’s emergence. As our understanding of the earlier stages of the disease improves – from the findings of studies like these – we move closer to finding new, more effective treatments for this prevalent and debilitating condition. There are currently three trials in action exploring the effectiveness of drugs on different targets identified by studies like these.
A test for Alzheimer’s, as with the test for Huntington’s, presents both advantages and disadvantages. It would allow time to plan for long term care, to inform family members and to organise affairs. Unlike Huntington’s, a genetic and therefore inevitable disease for those with the gene, Alzheimer’s could be delayed or even prevented through diet and exercise. It could also help their family to recognise the symptoms earlier, and allow them to identify them as signs of Alzheimer’s.
The question still remains, however – how much do we really want to know about our own future?
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Mapstone, M., Cheema, A., Fiandaca, M., Zhong, X., Mhyre, T., MacArthur, L., Hall, W., Fisher, S., Peterson, D., Haley, J., Nazar, M., Rich, S., Berlau, D., Peltz, C., Tan, M., Kawas, C., & Federoff, H. (2014). Plasma phospholipids identify antecedent memory impairment in older adults Nature Medicine, 20 (4), 415-418 DOI: 10.1038/nm.3466
Andrews, L. B. (1999). The Clone Age. New York: Henry Holt and Company.
Hereditary Disease Foudation (2008). Guidelines for genetic testing of Huntington’s disease. Retrieved March 19, 2014, from Hereditary Disease Foundation: www.hdfoundation.org/html/hdsatest.php
Alzheimer’s Society (2014). Demetia 2013: The hidden voice of lonliness. Retrieved March 19, 2014, from Alzheimer’s Society: www.alzheimers.org.uk/infographic