Child's eyes
According to the developmental origin of health and disease hypothesis, child development and ageing are both related in a cause-and-effect manner. Meaning that healthier development builds up a better stock of physical, cognitive and mental health. Amit Dave/Reuters

A new research paper published online in the Computational and Systems Biology, Epidemiology and Global Health journal has thoroughly explored a significant link between the biological age and the development of children.

In contrast to chronological age, the biological age in adults is primarily associated with general health and how resistant their immune system is to disease. However, it has been discovered using geroscience that children may be at risk of severe health complications if their biological age exceeds their chronological age.

Geroscience is based on the hypothesis that biological ageing causes the breakdown of bodily processes, which subsequently results in multiple diseases that are dismissed as part of old age. There have been many scientists who have tried to ascertain biological ageing markers in order to preserve health for longer in later life.

According to the published paper, the study's primary purpose was to clarify the relationship between biological age, DNA and telomere length, and the developmental outcomes of a child's growth, mental health, behaviour, cognition, fat deposition, puberty and organ function.

Over 1,100 children aged between 5 and 12 participated in the study, all from European centres in the UK, France, Spain, Norway, Greece and Lithuania. All children involved were part of the Human Early Life Exposure (HELIX) study.

The length of the telomere, a region of repetitive DNA sequences at the end of a chromosome, was measured using a quantitative polymerase chain reaction (qPCR), blood DNA and gene expression were measured microscope slides, whilst protein and metabolites were measured using a variety of targeted assays to monitor reactions. The ageing of DNA, telomere length and gene expression was assessed by using multiple biological clocks including Horvath's skin and blood clock, a device that has modernised biological age measurement.

Child in a science room
Alongside adults, children also experience biological ageing across a much broader spectrum. For instance, increased fat deposition correlates with faster biological ageing. Gonzalo Fuentes/Reuters

Also involved in the study were two new biological clocks, the transcriptome and immunometabolic molecular clocks, which accurately predicted the chronological age. Among the associations with health risk factors, higher birth weight was associated with greater immunometabolic age, along with higher smoke exposure being linked to greater DNA ageing.

In terms of child developmental measures, all biological age markers were associated with greater BMI and fat mass, and all markers, except for telomere length, were associated with a greater height in the children. Also, the immunometabolic age was associated with effective memory and reduced irresponsibility, while the DNA age was associated with greater irresponsibility and poorer externalising behaviours.

Despite the biological ageing and clock markers poorly correlating with each other, it was quickly established that all of the markers were unequivocally linked to increased weight gain and fat deposition. The results of the transcriptome clock also proved that gene expression is closely linked with ageing.

The study concluded that in children, as in adults, biological ageing is a complex and multi-faceted process, and obesity is a prevalent correlation of accelerated biological ageing. BMI is a persistent marker of this ageing process and punctuates the role of dysfunctional metabolism in age-related physiological decline.

Ultimately, this unearthed pattern of associations suggests that accelerated immunometabolic age may be beneficial towards certain aspects of a child's development.