How does our early life affect the way we age?

By Megan Widdows

Aging is the pro­cess of get­ting older and it hap­pens to all of us. It is a cumu­lat­ive pro­cess, that res­ults from com­plex bio­lo­gic­al pro­cesses that occur through­out our life. As we get older, we get slower, less agile, our men­tal capa­city decreases and we face high­er risks of devel­op­ing dis­ease. Some of these com­mon age-related dis­eases in humans include hear­ing loss, catar­acts, osteoarth­rit­is, type 2 dia­betes and dementia. 

How­ever, not every­one ages at the same rate and there is no set age at which we all begin to decline. This is partly due to genet­ic dif­fer­ences between indi­vidu­als and may explain why mem­bers of some fam­il­ies tend to live to see one-hun­dred years whilst mem­bers of oth­er fam­il­ies rarely live longer than 75. How­ever, the envir­on­ment we live in is thought to play an even more import­ant role than our genes in determ­in­ing how we age. 

The envir­on­ment is basic­ally the sur­round­ings and con­di­tions in which a per­son, anim­al or plant lives and oper­ates. For people, this includes our phys­ic­al envir­on­ment, such as access to clean air and water and healthy liv­ing con­di­tions that are not affected, for example, by damp or haz­ard­ous sub­stances such as asbes­tos. It also includes our social and eco­nom­ic envir­on­ment, includ­ing access to edu­ca­tion, sup­port net­works from fam­ily and friends, our job and income level, fin­an­cial secur­ity and self-con­fid­ence. Per­son­al beha­viour and life­style choices such as the food we eat, con­sump­tion of alco­hol or drugs, smoking and exer­cising, or lack there­of, also con­trib­ute to our unique environment. 

Through­out our lives, we all encounter dif­fer­ent situ­ations and behave in dif­fer­ent ways and, as a res­ult of our unique com­bin­a­tion of genet­ics and envir­on­ment, this can have vari­able con­sequences for our health and the way we age. We already know that liv­ing in a high­er qual­ity envir­on­ment dur­ing the later stages of life reduces the rate of age-related decline in people. For us, a bet­ter envir­on­ment might involve eat­ing health­ily, reg­u­lar exer­cise and hav­ing a sup­port­ive envir­on­ment that encour­ages and enables older people to con­tin­ue doing the things they enjoy. 

How­ever, the envir­on­ment doesn’t only affect your rate of age-related decline when you get old. Some sci­ent­ists believe that envir­on­ment­al factors may begin influ­en­cing how we age from very early dur­ing our devel­op­ment – even before we are born. 

To under­stand what role our early envir­on­ment plays in our decline into old age, sci­ent­ists stud­ied the effect that dif­fer­ent envir­on­ments exper­i­enced dur­ing the devel­op­ment­al peri­od had on rates of aging and repro­duct­ive decline in later life, with devel­op­ment­al peri­od classed as being from gest­a­tion to sexu­al matur­ity. To do this, they con­duc­ted a study that com­pared the effects of dif­fer­ent envir­on­ments exper­i­enced dur­ing the devel­op­ment­al peri­od on sur­viv­al and declines in repro­duct­ive suc­cess with age across four­teen spe­cies of wild birds and mam­mals includ­ing red deer, moun­tain goats, the Asi­an ele­phant and tawny owls.

Sen­es­cence is a word that is often used inter­change­ably with aging. It describes the changes that occur in the old age of an organ­ism, that cause increased vul­ner­ab­il­ity to chal­lenges. Such changes might be, for example, increased risk of dis­ease and the reduced abil­ity to defend one­self. These changes decrease the over­all chance of survival. 

Repro­duct­ive sen­es­cence is any reduc­tion in the abil­ity to repro­duce that occurs as an organ­ism gets older. An extreme example of this is the men­o­pause, where females of some spe­cies under­go hor­mon­al changes that com­pletely pre­vent fur­ther repro­duc­tion. In people, exper­i­en­cing a poor envir­on­ment dur­ing devel­op­ment has been linked to hav­ing an increased risk of devel­op­ing type 2 dia­betes and car­di­ovas­cu­lar dis­ease in later life, as well as a reduc­tion in life expect­ancy. It is also linked to early men­o­pause in women. In oth­er anim­als, good envir­on­ment­al con­di­tions, such as high nutri­ent avail­ab­il­ity, dur­ing devel­op­ment have been shown to have a pos­it­ive impact on the anim­al, which can last long after the devel­op­ment peri­od has ended. This is known as the “sil­ver-spoon effect”, and it has been shown to have many pos­it­ive impacts on early and middle life in anim­als and people. 

Sur­pris­ingly though, a study by two sci­ent­ists in 2018 showed that the qual­ity of envir­on­ment exper­i­enced dur­ing devel­op­ment had no detect­able effect on the rate of gen­er­al aging or lifespan of the anim­als. Instead, it found that those anim­als that exper­i­enced a good qual­ity envir­on­ment dur­ing devel­op­ment ten­ded to have faster rates of repro­duct­ive decline, mean­ing they are less likely to repro­duce in later life.  How­ever, size of this effect was only small, prob­ably reflect­ing that a mul­ti­tude of factors, both genet­ic and envir­on­ment­al, play a role in determ­in­ing the rate of repro­duct­ive decline. 

If hav­ing a bad qual­ity devel­op­ment­al envir­on­ment does slow the rate of aging, how does it work? One the­ory is that there may be a link between the abil­ity to sur­vive harsh con­di­tions and the abil­ity to sur­vive into old age. Indi­vidu­als that are able to sur­vive poor con­di­tions dur­ing devel­op­ment are also more likely to age more slowly and sur­vive longer. So although the devel­op­ment­al envir­on­ment may not dir­ectly affect the rate of age-related decline, it could still have far-reach­ing effects that last right up to the final stages of life. This has import­ant rami­fic­a­tions for our under­stand­ing not only of anim­al devel­op­ment, but also of repro­duct­ive and age-related decline in humans. 

The study men­tioned in this art­icle can be found here. A gloss­ary of terms is provided below.

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