The Biology of Aging
Aging is not simply the passage of time — it is a collection of molecular and cellular processes that accumulate damage, exhaust repair systems, and ultimately compromise function. The Lopez-Otin hallmarks of aging framework identifies twelve interconnected mechanisms, from telomere shortening and DNA damage to altered nutrient sensing, mitochondrial dysfunction, and cellular senescence.
Cellular senescence is a state where damaged cells stop dividing but refuse to die. These zombie cells accumulate with age and secrete inflammatory signals that damage neighboring tissues — a phenomenon called the senescence-associated secretory phenotype (SASP). Research from the Mayo Clinic showed that clearing senescent cells from old mice extended healthy lifespan by 36% and delayed multiple age-related conditions simultaneously.
Epigenetic clocks offer a new way to measure biological age that may be more informative than chronological age. By examining methylation patterns at specific DNA sites, these clocks can estimate how old a person’s cells are biologically. People whose biological age is younger than their chronological age have lower risks of age-related disease and mortality in large prospective studies.
