Editing Senescence (section)

{{short description|Deterioration of function with age}}
{{about|the aging of whole organisms including animals|aging specifically in humans|Ageing|plants|Plant senescence|cells that stop dividing|Cellular senescence|bacteria|Bacterial senescence}}
{{Use American English|date=May 2024}}
{{Use dmy dates|date=May 2024}}
{{cs1 config|name-list-style=vanc|display-authors=3}}

'''Senescence''' ({{IPAc-en|s|ɪ|ˈ|n|ɛ|s|ə|n|s}}) or '''biological aging''' is the gradual deterioration of [[Function (biology)|functional]] characteristics in living organisms. Whole [[organism]] senescence involves an increase in [[mortality rate|death rates]] or a decrease in [[fecundity]] with increasing age, at least in the later part of an organism's [[biological life cycle|life cycle]].<ref name=":0">{{Cite journal|last=Kirkwood|first=T. B. L.|date=1977|title=Evolution of ageing|url=http://dx.doi.org/10.1038/270301a0|journal=Nature|volume=270|issue=5635|pages=301–4|doi=10.1038/270301a0|pmid=593350|bibcode=1977Natur.270..301K|s2cid=492012|access-date=31 January 2022|archive-date=15 November 2023|archive-url=https://web.archive.org/web/20231115062848/https://www.nature.com/articles/270301a0|url-status=live|url-access=subscription}}</ref><ref name="nelson_2017">{{cite journal | vauthors = Nelson P, Masel J | title = Intercellular competition and the inevitability of multicellular aging | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 114 | issue = 49 | pages = 12982–7 | date = December 2017 | pmid = 29087299 | pmc = 5724245 | doi = 10.1073/pnas.1618854114 | bibcode = 2017PNAS..11412982N | doi-access = free }}</ref> However, the resulting effects of senescence can be delayed. The 1934 discovery that [[calorie restriction]] can [[Life extension|extend lifespans]] by 50% in rats, the existence of species having [[negligible senescence]], and the existence of potentially immortal organisms such as members of the [[genus]] ''[[Hydra (genus)|Hydra]]'' have motivated research into [[Life extension|delaying senescence]] and thus [[age-related disease]]s. Rare human mutations can cause [[accelerated aging disease]]s.

Environmental [[Gerontogens|factors]] may affect [[aging]] – for example, overexposure to [[ultraviolet radiation]] accelerates [[skin aging]]. Different parts of the body may age at different rates and distinctly, including [[Aging brain|the brain]], [[Cardiovascular disease#Age|the cardiovascular system]], and <!--Skeletal muscle#Atrophy [[Aging musculature]]-->muscle. Similarly, functions may distinctly decline with aging, including [[Aging movement control|movement control]] and [[Memory and aging|memory]]. Two organisms of the same species can also age at different rates, making biological aging and chronological aging distinct concepts.