Tarín Juan J, Gómez-Piquer Vanessa, García-Palomares Silvia, García-Pérez Miguel A, Cano Antonio
Department of Functional Biology and Physical Anthropology, Faculty of Biological Sciences, University of Valencia, Burjassot, Valencia 46100, Spain.
Reprod Biol Endocrinol. 2014 Aug 25;12:84. doi: 10.1186/1477-7827-12-84.
Most human demographic data, particularly those on natural fertility populations, find no relationship or even a positive association between fertility and longevity. The present study aims to ascertain whether there is a trade-off between fertility and longevity in the mouse model.
The study was focused on the first litter produced by 10- to 14-wk-old hybrid (C57BL/6JIco female X CBA/JIco male) mice. A single female/male per litter was individually housed with a male/female at the age of 25 and 52 wk, respectively, until the end of reproductive life in females or natural death in males under controlled housing conditions. Post-reproductive females and virgin mice were reared until natural death. Cox regression models with forward stepwise variable selection were fitted to examine the effect of several fertility variables on expectation of survival times.
Virgin females displayed higher life expectancy than virgin males. The relative risk of dying for a virgin male at a particular age was 2.116 [99% confidence interval: 1.317, 3.398] times that of a virgin female. No significant differences on expectation of survival times between virgin and mated females, and between virgin and mated males were found. Furthermore, total number of pups at weaning and total number of litters produced by a dam/stud, time interval between mating and last litter, time interval between litters, and age at last litter were not significant predictors of expectation of survival times in both mated females and mated males.
Like in most human studies, the present study evidences no relationship between total number of offspring/litters produced by a dam/stud and expectation of survival times. Moreover, the present data are in agreement with the general phenomenon of a bias in life expectancy in favor of females.
大多数人类人口统计学数据，尤其是那些关于自然生育人群的数据，并未发现生育与长寿之间存在关联，甚至发现二者呈正相关。本研究旨在确定在小鼠模型中生育与长寿之间是否存在权衡关系。
本研究聚焦于10至14周龄的杂种（C57BL/6JIco雌性×CBA/JIco雄性）小鼠所产的第一窝幼崽。每窝中的一只雌性/雄性小鼠分别在25周龄和52周龄时与一只雄性/雌性小鼠单独饲养，直至雌性小鼠生殖寿命结束或雄性小鼠自然死亡，饲养条件可控。繁殖后的雌性小鼠和未交配的小鼠饲养至自然死亡。采用向前逐步变量选择的Cox回归模型来检验几个生育变量对生存时间预期的影响。
未交配的雌性小鼠比未交配的雄性小鼠寿命更长。在特定年龄，未交配雄性小鼠死亡的相对风险是未交配雌性小鼠的[99%置信区间：1.317, 3.398]2.116倍。未发现未交配雌性与已交配雌性之间以及未交配雄性与已交配雄性之间在生存时间预期上存在显著差异。此外，断奶时幼崽的总数、母鼠/种公鼠所产窝数的总数、交配与最后一窝之间的时间间隔、各窝之间的时间间隔以及最后一窝时的年龄，均不是已交配雌性和已交配雄性生存时间预期的显著预测因素。
与大多数人类研究一样，本研究表明母鼠/种公鼠所产后代/窝数的总数与生存时间预期之间不存在关联。此外，本研究数据与寿命偏倚有利于女性的普遍现象一致。
