Institute of Cytology and Genetics of the SB RAS, Novosibirsk, Russia, email@example.com
At present time global demographic crisis in developed countries including Russia is accompanied with a decrease in reproductive potential of human societies. For example, 10-15% of couples are infertile and their number is steadily increased. Recent data indicate that mean sperm density decreased 50% and the incidence of genitourinary abnormalities and testicular cancer increased in human males over the past decades. What is perhaps more surprising is that the increasing incidence of oligospermia (sperm concentration below the level of 20 million ⁄mL) has been observed among men aged 18–25 years in different European countries (15-20%). The same data have been obtained in the young Russian citizens living in Siberian cities (Osadchuk et al., 2010, 2011). This is a high proportion of males with subfertility is thus a very significant global problem and, most worryingly, reports suggest that its prevalence is increasing. The remarkable decrease in reproductive potential of human being over a relatively short period of time may be due to social factors. In particular, the changes in reproductive behaviour and lifestyle-related factors were suggested to be responsible for this process.
Social surroundings form a model of reproductive behaviour in modern young people. The analysis of reproductive intentions in young men living in the cities of Novosibirsk, Kemerovo, Ulan-Ude and Yakutsk showed that the mean age at first intercourse is around 16-17 years, while the mean age at first marriage is 23-25 years. Couples having children consist of not more 9-16% for investigated groups (as a rule they have one or rarely two children). The study also revealed no impact of ethnic or socio-cultural factors on reproductive intentions in Siberian youth. So, we found that the reproductive intentions and motivations among Siberian young men directed to a volitional restriction of birth rate without sexual abstinence, and couples tend to postpone these births until a later age.
Volitional family planning and reduced family size might result in a gradual increase in the prevalence of subfertility by selective forces, because the most fertile part of the population reproduce less while the subfertile continue to get the same (low) number of children. The most probable way resulting in reduced potential fertility during the past century could be selection for social factors (the lengthening of the period of education, the uncertainties of labour market, the availability of effective contraceptive, the desire for making a career). The changes in reproductive behaviour, that manly determined by social milieu, are involved in this process.