Research Suggests Women Who Have Fewer Children Live Longer
Birth rates are one of the reasons why women outlive men, according to a study conducted by Utah Population Database from Uppsala University. The study, which used a distinct demographic record of 140,600 individuals is published in the Scientific Reports.
Through a distinct demographic record, the study showed that men born in the early to mid 1800s had lived two years longer than women. However, this was reversed over time, and women born in the early 1900s were shown to outlive men by four years, Science Daily reported.
The birth rates during this period decreased from 8.5 percent in the early 1800s to 4.2 percent children per woman in the early 1900s. The female lifespan has increased, while the male lifespan remained stable. This has supported the theory that the differential costs of reproduction between both genders lead to the shifting patterns of sex differences in terms of lifespan throughout the human populations.
The gathered data also suggested that women who gave birth to 15 children and more lived on an average of 6 years shorter than women who had a single child. Also, there was no direct relationship between the number of children fathered and the lifespan in men.
According to the life-history theory, every individual has limited resources which may be invested in reproduction, including the repair of the body. This implies that low birth rate should benefit the female lifespan, although females pay the higher costs of reproduction than the males, First Post reported.
The relation of birth rate to the study of lifespan shows the importance of considering the biological factors when explaining the reasons behind the shift of mortality patterns among human populations. The results give some serious implications for the demographic forecasts, since the pattern of fertility and expected lifespans continue to change. Furthermore, it suggests that as more countries go through a demographic transformation, the overall sex differences in lifespan may also increase.