Chronological age is the number of years a person has been alive. In contrast, biological age refers to how old a person seems, based on several factors, like how your chromosomes have altered over time. In a study, the researchers measured DNA methylation to calculate the women’s biological age (Kresovich et al., 2019). DNA stands for deoxyribonucleic acid, a substance that is the main part of chromosomes. DNA methylation is a chemical change to DNA that is part of the normal aging process. DNA methylation that happens in abnormal patterns — indicating some DNA that should methylate doesn’t, and DNA that should not methylate does — has been linked to cancer. Scientists think that DNA methylation and biological age may be affected by exposure to things in the environment, including sunlight, automobile exhaust, alcohol, and chemicals in food, plastics, and water. In this study, the researchers estimated the women’s biological ages using three measures called “epigenetic clocks.” (Kresovich et al., 2019)
Epigenetics is the study of changes in a living thing caused by changes in how genes are expressed, rather than changes to the genes themselves. The epigenetic clocks measure methylation at specific locations in the DNA.
Reference
Kresovich, J. K., Xu, Z., O’Brien, K. M., Weinberg, C. R., Sandler, D. P., & Taylor, J. A. (2019). Methylation-Based Biological Age and Breast Cancer Risk. JNCI: Journal of the National Cancer Institute, 111(10), 1051–1058. https://doi.org/10.1093/jnci/djz020
Breast Cancer org (2019). Older Biological Age Compared to Chronological Age Linked to Increased Breast Cancer Risk. https://www.breastcancer.org/research-news/biological-vs-chronological-age-and-risk