Long-Term Study Finds Aging Follows Distinct Molecular Paths

A long-term molecular study has found that healthy people can follow substantially different biological aging trajectories, even when they are the same age. The research, led by investigators at King’s College London and published in Science, tracked changes in the same 335 TwinsUK participants over eight years.

Researchers repeatedly measured blood RNA levels, the activity of approximately 16,000 genes and hundreds of metabolites. This multi-omic approach allowed the team to examine how molecular patterns changed within individuals over time rather than relying only on comparisons between people of different ages.

The results showed that some participants experienced sharply different—and in some cases opposite—molecular changes. The researchers reported variation in the way genetic factors and environmental influences interacted throughout life, suggesting that aging does not follow one uniform molecular sequence.

Differences were also seen in immune-related biology. Changes over time were not consistent across innate and adaptive immune cells. Innate immune cells provide an early defense response, while adaptive immune cells develop a more learned and memory-based response. The contrast suggests that different components of the immune system may age along separate molecular paths.

The study also identified examples involving genes associated with disease-related processes. Participants with variants in CXCL9, a gene linked in the report to cardiac aging, showed different courses of molecular change. In some individuals, levels of TP53—a tumor suppressor gene—declined with age. The researchers said such shifts could alter cancer risk, although the findings do not establish that the observed molecular changes caused cancer or predict disease in a particular person.

Environmental exposure was another factor associated with changing molecular profiles. The researchers observed correlations between shifts in blood levels of PFAS, often called “forever chemicals,” and changes in molecular measurements over time. According to the report, these findings indicate that environmental exposures can leave detectable marks at the molecular level. They do not, by themselves, establish that PFAS caused the specific biological changes observed.

The findings support the idea that molecular aging is influenced by both inherited variation and changing surroundings. Researchers said that mapping individual trajectories could eventually help distinguish healthy aging from early disease-related changes and inform more personalized approaches to risk assessment. Those applications remain future possibilities; this study did not test a treatment or demonstrate that changing any measured marker would extend lifespan or prevent disease.

The study, titled “Longitudinal dynamics of gene expression and metabolomics in an ageing population cohort,” was published in Science in 2026.