Biological age is the result of a biological clock; it is an important concept and a practical tool for age research. But how exactly is biological age calculated, what influences it, how does it differ from chronological age and what can we deduce from this?

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Biological age vs. chronological age

Since everyone ages at different rates, the differences between chronological and biological age can differ.

The chronological age is the number that results from the date of birth and on which we have no influence. Biological age, on the other hand, can certainly be influenced. It reflects a body's overall health status and changes in response to lifestyle and health status. A healthier diet, regular exercise and good, adequate sleep can actively reduce biological age.

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Aging biomarkers

To determine biological age, longevity researchers first had to identify standardized metrics or biomarkers for cell aging. Aging biomarkers are well-researched principles of aging at the cellular level; they respond measurably to aging and age-related symptoms. These aging biomarkers help us understand and develop so-called biological clocks, which in turn measure and calculate our biological age.

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An accurate understanding of aging biomarkers and cellular health can enable early diagnosis of various diseases and help combat age-related diseases such as cancer, cardiovascular diseases, and neurological disorders.

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Epigenetic data

Epigenetic data is used to calculate biological age, in particular DNA methylation derived from a blood sample or another source. DNA methylation is basically a chemical change in DNA — it does not change the sequence of the DNA, but regulates which genes are switched on and which are switched off. And there are certain areas of the genome where methylation increases with age and other areas where methylation decreases with age.

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When you look at the entire genome, there are very specific patterns of DNA methylation and how it changes with age: Using these patterns, you can predict a person's biological age based on hundreds of thousands of these sites, which are a reflection of overall health and functioning.

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Tests offered at home measure biological age in saliva as an indicator of a person's total biological age, while most scientific studies use blood for this measurement. However, the exciting thing about using DNA methylation to measure biological age is that different biological ages can be calculated for different parts of the body. This enables a more differentiated understanding of a person's biological age in the various organs and therefore a more comprehensive understanding of their overall health and aging. The biological age of the blood can be determined on the basis of a blood sample. With a skin sample, a saliva sample or a cheek swab, the biological age can be determined on the basis of these cells. There are currently no biopsies of various organs, but a different biological age could be determined for the heart than for the liver or even the brain, and that could have further effects on the future health of these specific organs.

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DNA methylation

DNA methylation is a fundamental concept in epigenetics. Gene expression refers to the extent of protein production that comes from a gene. A gene can only produce proteins when specific enzymes bind to its DNA. If you wanted to switch off a gene so that it no longer produces proteins, you would have to prevent enzymes from binding to its DNA. When you attach methyl groups to the DNA of a gene, it is difficult for proteins to bind. Increasing the level of DNA methylation can therefore effectively reduce protein production and thus gene expression.

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Ideally, we would like to see lower methylation levels for genes with protective effects, such as tumor suppressor genes, and higher methylation levels for genes that can have negative effects, such as tumor promoter genes. However, DNA is damaged as we age and although it is also repaired again, the DNA repairs are rarely perfect and often result in different methylation patterns. These critical changes can accelerate the aging process. In fact, most age-related changes we experience are due to epigenetic changes.