What causes some individuals to age more successfully than others is a question behind the efforts in ageing research. A study published in Translational Psychiatry aimed to identify traits and lifestyle factors associated with different ageing trajectories.

Each year our birthday marks a turn on the chronological clock, but is the condition of our organism true to the age on the birthday cake? Epigenetic age is explained as the physiological age of an organism which can differ from chronological age. A way to measure epigenetic ageing is with epigenetic clocks, which at first used mostly chronological age as a reference to calculate epigenetic age, but lately have been incorporating phenotypes like blood cell profiles and inflammatory markers. One of the newer types of clocks, called DNAm PhenoAge is aimed to capture a more precise biomarker that can differentiate morbidity and mortality among individuals of the same chronological age.

It has been acknowledged that childhood traits and circumstances like lower intelligence or childhood deprivation can have a negative impact on health and morbidity later in life. This led researchers to hypothesize that these factors can also impact an individual’s epigenetic age which would show in their PhenoAge results.

To investigate this, researchers used The Lothian Birth Cohort 1936 which is a longitudinal study of ageing, valuable as it contains information on general cognitive ability and social circumstances of its participants at the age of 11. A total of 1091 participants of the original study was recruited at the mean age of 70 years. They were examined on physical and health status, cognitive abilities, genetics, lifestyle factors and psycho-social aspects of ageing. Participants were re-examined at the ages of 73, 76 and 79.

An association study was done with the collected data; participants’ genetic variants were observed to see if they are associated with any traits. Results showed that accelerated epigenetic age, physiological age of the organism, was related to lower IQ scores at 11 as well as lower levels of physical activity later in life, but significant correlations were found also between accelerated epigenetic PhenoAge and a number of physical, cognitive and lifestyle traits. Cognitive ability at age 11 and the number of years of education was a trait that stood out.

“The association between DNAm PhenoAgeAccel with IQ measured almost 60 years previously is a key finding and is indicative of a lifelong, enduring association between cognition and epigenetic ageing”, authors of the study noted. This supports previous findings indicating that general intelligence in childhood is associated with considerable life-course differences in health and morbidity. A possible explanation for this association could be in better health literacy and consequential disease management as well as higher socioeconomic standing.

As with much correlation-based research, there is a question of which came first, the chicken or the egg. It is both possible that individual differences in epigenetic age are caused by intelligence differences, or that both the intelligence and a more favourable epigenetic age score are the result of a shared genetic architecture or early environmental event. Nevertheless, authors conclude that “this novel epigenetic clock may be somewhat qualified in its capacity as a biomarker of physiological ageing.’’

The study, “Childhood intelligence attenuates the association between biological ageing and health outcomes in later life”, was authored by Anna J. Stevenson, Daniel L. McCartney, Robert F. Hillary, Paul Redmond, Adele M. Taylor, Qian Zhang, Allan F. McRae, Tara L. Spires-Jones, Andrew M. McIntosh, Ian J. Deary, and Riccardo E. Marioni.