Vitzthum Virginia J, Wiley Andrea S
Science Foundation, Arlington, VA, USA.
High Alt Med Biol. 2003 Summer;4(2):125-39. doi: 10.1089/152702903322022758.
It has been hypothesized that hypoxia reduces fertility, but comparative studies of high and low altitude populations have been unable to verify or refute this proposal because it is difficult to control for the behavioral and sociocultural factors that may also either underlie fertility differentials or compensate for physiological changes caused by varying partial pressure of oxygen. Taken collectively, estimates of fertility in populations exposed to chronic hypoxia range widely and do not suggest any reproductive patterns specific to high altitude. Here we review the available data from the Andes and the Himalaya on the proximate determinants of fertility, that set of factors through which any and all environmental, behavioral, and sociocultural factors must act to influence fertility levels. Although hypoxia could potentially affect some of these factors, there is no unequivocal evidence that this occurs in human populations indigenous to high altitude. At this time, it appears that local variations in infant feeding beliefs and practices, often coupled with prolonged breast-feeding, play a major role in determining fertility variation in Andean populations. In the Himalaya, large numbers of adults are not in sanctioned sexual unions as a consequence of polyandrous marriage practices and religious celibacy. The absence of a clear negative effect of hypoxia on fertility in populations indigenous to high altitude, even though migrants report reproductive difficulties, argues that these populations have adapted to the conditions at high altitude. The experimental and clinical evidence presented in this issue suggests proximate mechanisms by which such adaptation, shaped by natural selection and developmental processes, is possible.
据推测，低氧会降低生育能力，但对高海拔和低海拔人群的比较研究无法证实或反驳这一观点，因为难以控制那些可能是生育差异的潜在原因或补偿因氧分压变化所引起的生理变化的行为和社会文化因素。总体而言，暴露于慢性低氧环境下的人群的生育能力估计值差异很大，并未显示出任何特定于高海拔地区的生殖模式。在此，我们回顾了来自安第斯山脉和喜马拉雅山脉关于生育的直接决定因素的现有数据，这些因素是所有环境、行为和社会文化因素必须通过其来影响生育水平的因素集合。虽然低氧可能会潜在地影响其中一些因素，但没有明确的证据表明这种情况发生在高海拔地区的原住民人群中。目前看来，婴儿喂养观念和做法的局部差异，通常与延长母乳喂养时间相结合，在决定安第斯人群的生育差异方面起着主要作用。在喜马拉雅地区，由于一妻多夫制婚姻习俗和宗教独身主义，大量成年人没有处于被认可的性关系中。尽管移民报告有生殖困难，但高海拔地区原住民人群中低氧对生育能力没有明显负面影响，这表明这些人群已经适应了高海拔环境。本期所展示的实验和临床证据表明了由自然选择和发育过程塑造的这种适应得以实现的直接机制。
