Alzheimer's Disease: Who Needs Genetic Testing And What Does It Reveal?

Alzheimer's is one of the most progressive neurodegenerative diseases as it impacts millions across the globe. According to experts, lifestyle factors and other environmental elements contribute to this degenerative disease, but genetics also have a significant role.

But why is genetic testing important? “Genetic testing can give people insight into their inherent dispositions and risk profiles for developing Alzheimer's, especially in those with a family history,” said Dr. Shelly Mittal Mahajan, Lab Director and Clinical Lead at Mahajan Imaging Labs. According to the World Health Organisation, Alzheimer’s disease is the most common form of dementia and may contribute to 60–70 per cent of cases worldwide.

According to Dr. Mahajan, genetic testing is also recommended for individuals with a family history of Alzheimer's disease, especially if those affected were diagnosed before the age of 65 years. “Genetic Alzheimer's tends to begin early in life; however, a test may allow a level of assessment of the degree of risk. This can be very useful if diagnosed within the first line of relatives APOE-e4 is the most common gene associated with Alzheimer’s, but it does not guarantee the development of the disease,” she said. Around 20-25 per cent of those suffering from this debilitating condition have this genetic disposition.

In India, there are about 8.8 million people over 60 years diagnosed with dementia - which gives some indication that genetic clues do contribute to future planning and prevention strategies.

“The rising incidence of dementia - including Alzheimer's, necessitates a dedicated focus on spreading awareness and early intervention,” she said.

Genetic testing can identify two types of genes:

This is the most common gene implicated in Alzheimer’s. “There is a proven association between a copy or two of the APOE-e4 gene for the prevalence of risk, but again, it does guarantee the development of Alzheimer’s,” said Dr. Mahajan.

Those who have two or more copies of this gene – have a higher risk of developing the disease. Also, many inherit the gene but never develop Alzheimer’s, while others without the gene may still develop later in life.

These are associated with familial Alzheimer's disease or FAD - accounting for early onset Alzheimer's in only a few per cent of all cases. “Mutations in these genes ensure that Alzheimer's will be expressed if the genes are inherited, often under the age of 65. Though these mutations occur infrequently, they have a near 100 per cent chance of resulting in the disease if passed down,” said Dr. Mahajan.

Genetic testing gives valuable insight into the absence or presence of an inherent disposition for Alzheimer's. A positive result may promote a change in lifestyle towards improving cardiovascular health and cognitive activities that would hold off the onset of the disease.

Additionally, it helps in preparing, emotionally and financially, for what’s to come. However, genetic testing has its limits: a positive result, such as for the APOE-e4 gene, doesn't guarantee the development of the disease; and a negative result does not rule out the risk of developing it. Apart from this, a positive result may also cause considerable emotional stress; thus, genetic counseling is required to aid and assist individuals in understanding and managing the results.

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