Research results show that 'contraception' extends the lifespan of many mammals
In modern society, spaying and neutering are widely practiced as part of family planning and life planning, and new research on animals in zoos and other settings has shown that 'many mammals who are spayed or neutered or neutered live longer.'
Sterilization and contraception increase lifespan across vertebrates | Nature
Contraception and castration increase lifespan in mammals
https://www.mpg.de/25822909/1204-evan-contraception-and-castration-increase-lifespan-in-mammals-150495-x
Contraception May Extend The Life of Some Mammal Groups by 10% : ScienceAlert
https://www.sciencealert.com/contraception-may-extend-the-life-of-some-mammal-groups-by-10
Although lifespans vary among animals, generally speaking, animals that give birth to more offspring tend to have shorter lifespans, while animals that give birth to fewer offspring tend to have longer lifespans. One explanation for this tendency is that animals need to allocate their limited resources between 'reproduction' and 'self-sustaining,' and that spending energy on reproduction reduces the energy available for survival.
Reproductive activities such as mating, pregnancy, childbirth, and raising young require a great deal of energy, and even when not breeding, sex hormones affect growth and aging, consuming resources that would otherwise be used to maintain the body. This means that if an animal is unable to reproduce through spaying or neutering or other medical treatment, it could theoretically live longer.
To test this theory, an international team of researchers from the Max Planck Institute for Evolutionary Anthropology in Germany and the University of Otago in New Zealand analyzed records of 117 species of animals kept in zoos and aquariums around the world, as well as a meta-analysis of 71 published studies on sterilized animals, both bred in laboratories and in the wild.
The analysis found that continuous hormone treatment for birth control or permanent sterilization increased the animals' lifespan by an average of 10%. While the lifespan-enhancing effect of contraception has been observed in many mammalian groups, from primates to marsupials to rodents, the effects were particularly pronounced in some species. For example, in
'This study shows that the energetic costs of reproduction have a measurable, and sometimes large, impact on survival in mammals in general,' said Fernando Colchero, a co-author of the paper and a statistical and mathematical ecologist at the Max Planck Institute for Evolutionary Anthropology. 'By reducing investment in reproduction, we may be able to devote more energy to extending lifespan.'
While the lifespan extension effect of contraception occurred in both males and females, the underlying causes were different. Castration extended the lifespan of males, while vasectomy did not. This is thought to be due to the fact that sterilization during development reduces the secretion of the male hormone testosterone , eliminating its influence on key aging pathways and reducing the risk of risky behavior.
In contrast, in females, multiple types of sterilization and treatment have been shown to extend lifespan, likely due to reduced burdens of pregnancy, lactation, and menstrual cycles. However, ovariectomy-based sterilization, while extending lifespan, has been shown to impair health in later life, potentially explaining the increased susceptibility of postmenopausal women to frailty and chronic disease.
'Because this data was obtained from non-human animals, it is unclear whether similar results can be confirmed in humans. A study of eunuchs in the Korean peninsula before the 19th century showed that castrated men lived an average of 18% longer than uncastrated men, but the accuracy of historical records is debated. Furthermore, research has shown that surgical sterilization for benign conditions in women is associated with a reduction in lifespan of approximately 1%.'
The research team pointed out that 'reproduction is inherently costly, but human circumstances such as health care, nutrition, and social support can mitigate or alter these costs.'
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