How many years will I live? Biological, not chronological, age holds the key

The chronological age it is basically the time that has passed since our birth. If you came into the world on August 16, 1957, on the same date in 2022 you will be 65 years old. There is no discussion. Another thing is how old your cells, tissues, organs and systems are. This is what measures biological age. Differences in health status between people of the same age have to do with genetic predispositions and physiological responses to lifestyle, diet or sleep quality throughout life.

Knowing the biological age can predict the life expectancy of a person, according to the results obtained by an international team, with the participation of the Higher Council for Scientific Research (CSIC), which proposes two methods to estimate real aging with greater predictive power than the existing ones. The work is published in the journal «PNAS Nexus«.

The method takes into account health measures that can be obtained routinely and allows the use of more or fewer indicators depending on their availability. In the article we use nine flags: glycosylated hemoglobin (indicator of type 2 diabetes), cholesterol, blood pressure, pulmonary expiratory force, creatinine and urea nitrogen (indicators of kidney function), alkaline phosphatase and albumin (indicators of liver function), and C-reactive protein (indicator of inflammation)“, Hiram Beltrán-Sánchez, professor in the Department of Community Health Sciences at the University of California at Los Angeles (UCLA), explains to ABC Salud.

For the work, in which, in addition to the CSIC, scientists from UCLA and the University of Wisconsin participate, the largest health database in the United States, the National Health and Nutrition Examination Survey, has been used, which includes information on 9,389 men and women between 30 and 75 years old, between 1988 and 1994. In addition, they were followed up until December 2015 to find out how many of them had died.

The results, which have been obtained within the framework of the ERC Advanced Grant ECHO project, led by the CSIC researcher, provide relevant information on life expectancy from the age of 65. “From that age, when the biological age exceeds the chronological age by one year, it supposes a reduced life expectancy around two years. If the biological age is five years older, the decrease is even greater, living an average of nine years less. The surprising thing has been to verify how small increases in biological age with respect to chronological age translate into a increased risk of dying«, says Beltrán-Sánchez.

Until now, the methods that use biochemical indicators are based on imposing “arbitrary assumptions” between the relationship between biological and chronological age, explains the researcher. “Our method avoids the need to impose such assumptions about the relationship between these ages and provides tools to empirically test the validity of the assumptions. This means that our method is more flexible and allows us to more accurately capture physiological deterioration, which translates into a greater predictive power of the risk of dying«, he points out.

For this study, the researchers used the age of 65 as an example of what biological age may indicate in terms of risk of dying at a young age and years of later life. “That age is relevant because by that time it is very likely that you already have a accumulated biological deterioration over time so that we can then predict the risk of dying and the average lifespan“, explains Hiram Beltrán-Sánchez. On whether this system could be used to make predictions at younger ages, the researcher points out that, although it is possible, “if significant biological deterioration has not yet accumulated at younger ages, the prediction of life expectancy may not be accurate. «.

Biological age may also be a predictor of future diseases. The work proposes two ways to estimate biological age: dependent and non-dependent estimation. In both cases, biological deterioration is obtained through a structural equation model (a multivariate statistical analysis technique) and is then associated with additional information. “In the case of dependent estimation, for example, biological deterioration is associated with the risk of dying so that the resulting biological age is a very precise indicator of premature death. This form of estimation makes it possible to associate biological deterioration with other indicators of future disease instead of the risk of dying, for example, the risk of having a disability, cardiovascular disease, etc.”, he assures.

In addition, the dependent estimation pathway has the possibility, according to the researcher, of estimating the biological age associated with diseases that typically occur at older adult ages. “For example, one could use biochemical indicators in young people with the dependent method to estimate the biological age associated with cardiovascular disease. This would allow to create a general indicator of the possible risk of future disease », he affirms.

Will the day come when anyone can know their biological age and take steps to be better? The researchers acknowledge that more studies with a larger number of participants are needed to have better certainty with the predictions. “What is interesting about our method is that it uses indicators that could be altered both with medications (eg, cholesterol) and with dietary changes, exercise, etc.,” says Beltrán Sánchez.

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