Biodemography ProjectBiodemography of Infertility: Designing and Conducting an Internet Survey
Infertility and the declining birth rate
The reproductive aging among women in their 20s and 30s, in addition to the postponement of marriage and childbearing, has been speculated to contribute to the declining number of children in Japan. While the declining birth rate is acknowledged as a serious social problem, few research has been done on its underlying biological factors. Epidemiological research targeting Western populations has shown that along with aging, smoking and low body weight also increase the risk of infertility. Given the cultural differences between Japan and the Western countries, however, it is possible that lifestyle factors associated with infertility (e.g., body weight, coital frequency, and work hours) may affect Japanese women’s fertility differently. Using an epidemiological approach, this project aims to examine the effect of lifestyle factors, including work habits, stress, sleep, and smoking, on the risk of infertility among Japanese women.
Designing and conducting an Internet survey
An Internet survey was designed and conducted in the 2013 academic year. 10,467 women who were registered at Intage, Inc., between the ages of 20 and 44, and resided in Japan, were asked to participate in the study. 3,214 completed the survey (31% response rate). The questionnaire included: the waiting time to pregnancy, i.e. a period during which the respondent was sexually active without contraception and without becoming pregnant — 1-2 years suggests infertility; infertility risk factors such as gynecological illness or irregular periods; and lifestyle factors such as sleep, work hours, smoking, alcohol consumption, BMI, stress, etc. (Slama et al. 2012). The presence or absence of a partner, birth/miscarriage/abortion timing, lactation period, history of contraceptive/fertility surgery, and frequency of sexual intercourse were also included as proximate determinants of waiting time to pregnancy (Bongaarts et al. 1983).
Future plans
Beginning 2014, we plan to present our results both in Japan and overseas. Using a micro-simulation model with Japanese demographic information, we plan to estimate the changes in the infertility rate as we adjust each lifestyle parameter (e.g., by lowering the age of planned pregnancy by two years, or lowering the proportion of smokers by 10 percentage points, etc.). We believe that measuring the effect of delayed childbearing on the infertility rate, for example, could help us not only construct a better family policy, but also help women’s reproductive health and well-being.
References
- Bongaarts, J., and R. G. Potter. 1983. Fertility, Biology, and Behavior. NY: Academic Press.
- Slama, R. et al. 2012. Estimation of the Frequency of Involuntary Infertility on a Nation-wide Basis. Human Reproduction. 1489–1498.
