How is telomere length associated with cellular aging?

Telomere length is closely associated with cellular aging because telomeres act as a biological clock for cell division. As cells divide, telomeres shorten, which ultimately limits the number of divisions a cell can undergo. Once telomeres reach a critically short length, the cell enters a state of senescence, in which it no longer divides, or it undergoes apoptosis. This process is a protective mechanism to prevent the accumulation of mutations and the potential for cancer, but it also contributes to aging by limiting the regenerative capacity of tissues. Shorter telomeres are associated with age-related diseases and overall aging.