Genetic testing for a long life

Genetic test for a long life

Genetic profiles for four of the study participants. Depending on which set of gene segments is considered, the (calculated) probability that a person belongs to the group of 100-year-olds changes. This is easy to understand: a gene variant that is more widespread among people who have grown very old than in the control group is better suited as a marker for a potentially long age. (Graphic: Boston University School of Public Health)

Researchers filter the three billion or so base pairs in humans to find out which gene segments are characteristic of a potentially long life

If you want to grow old, you should drive carefully, stop smoking and eat healthily – but no health nut can guarantee that a person will celebrate his or her hundredth birthday in a reasonably fit condition. This is due to the fact that old age is not only a question of personal lifestyle, but also depends on genetic predisposition.

Unfortunately, there is no such thing as the centenarian gene – rather, a whole series of innate characteristics must come together so that an individual is very likely to still see his great-great-grandchildren. For example, one should not be predisposed to cardiovascular risks by one’s parents – in general, it would be ideal if one’s own genome did not show any susceptibility to the typical diseases of old age. For it is not old age that kills us, but rather signs of physical failure that accumulate or fail to appear depending on predisposition and age.

However, a certain gene variant is not a priori evil – under certain circumstances (think of sickle cell anemia, a hereditary disease that can protect its carrier from malaria infections), an otherwise unfavorable modification turns out to be life-saving. Therefore, it is currently hopeless to analytically hunt for genes that are important for healthy aging. Nevertheless, in the current ie of the renowned science magazine Science U.S. researchers able to tell with 77 percent certainty whether a person belongs to the over-100s group by looking at 150 different gene segments.

Spam diagnosis in the genome

Their trick: the scientists did not even bother with the analysis of individual sections. Instead, they used statistical methods, such as those used in spam diagnosis. Spam mails are no longer classified according to the presence of "sex" or "penis" in the text – instead, Bayesian filters construct a probability model from the presence and absence of certain terms, which ultimately sorts a single message into the spam or ham box. In order to train a Bayesian filter in a somewhat useful way, it should be trained with a few hundred spam and ham mails – and this is exactly what the age researchers did.

For these purposes, 801 between 95 and 119 years old participants of the New England Centenarian Study provided useful data material as "Spam" and 926 control subjects as "Ham. The procedure was complicated somewhat because the "language" of the genome comprises considerably more words than our everyday language – the researchers referred to 295.000 gene segments (SNPs) into the statistical analysis.

No rare trait at all

It turned out that a selection of about 150 specific SNPs is sufficient for a fairly reliable assignment; the addition of further sections does not improve the significance of the results. Genetic material comes from very different regions. Only 77 of the SNPs are found in genes whose function is already known. This means that a given genome can be predicted with 77 percent certainty to have at least the potential to live to a ripe old age.

Genetic test for a long life

In a second step, the researchers sorted the 100-year-olds into 19 different groups that differed significantly in terms of the signs of old age they had to contend with, such as dementia or high blood prere, for example. The hope: With such a profile, people could perhaps be shown an individually tailored path to old age in the future. (Graphic: Boston University School of Public Health)

In fact, this is not such a rare trait: A comparison of these specific segments with several hundred randomly selected individuals from another database showed that 15 percent of the test persons have at least a genetic chance of reaching an unusually high age of more than 50 percent.

But the researchers were able to show another interesting perspective: The nearly 1000 over-100-year-olds love statistically divided into 19 clusters, each of which could represent different paths to old age. In the future, the scientists hope to be able to derive personalized recommendations on how a subject can most safely realize his or her potential for a long life.

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