The water used to be wetter too…
A systematic review and meta-analysis of data collected from 1973 to 2011 conducted by researchers at the University of Jerusalem and the Mount Sinai Clinic showed that during this period the sperm concentration in Western men decreased by more than 50%. These data indicate a significant deterioration in men's reproductive health, which has serious consequences beyond the issues of fertility and reproduction. According to the authors, the study of the causes of the ongoing deterioration of sperm quality and the possibilities of its prevention is an urgent task.
As part of their work, they screened 7,500 studies and applied the meta-regression method to analyze 185 studies conducted between 1973 and 2011. According to the results of the analysis, during the specified period, the sperm concentration in men from North America, Europe, Australia and New Zealand, selected regardless of fertility level, decreased by 52.4%, and the total number of spermatozoa – by 59.3%. At the same time, such trends are not observed in the male population of South America, Asia and Africa, where significantly fewer studies have been conducted.
In addition, the collected data indicate that in recent years the rate of decline in sperm quality has not decreased.
While the decrease in sperm cell count was first discovered in 1992, until today this issue has been controversial due to the limitations of early studies. However, in their work, the authors used a wider range of data and powerful meta-regression methods of statistical analysis, taking into account all the assumptions made in the studies, as well as making adjustments for factors potentially contributing to the identified trend, such as age, duration of abstinence, as well as population choice.
The trends identified by the researchers are very important for the health of the population. Firstly, they indicate an increase in the proportion of men whose sperm cell count is below the threshold for reproductive failure or infertility. Moreover, data have recently been obtained according to which poor sperm quality is associated with an increased risk of hospitalization and death.
As part of their work, the authors did not study the causes of the observed decrease, but earlier studies revealed a significant relationship between sperm cell count and environmental and lifestyle factors, including exposure to chemical compounds during perinatal development, as well as pesticides, smoking, stress and obesity in adulthood. Therefore, sperm cellularity can be a sensitive indicator of the environmental impact on men's health throughout life.
Article by Hagai Levine et al. Temporal trends in sperm count: a systematic review and meta-regression analysis published in the journal Human Reproduction Update.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru Based on the materials of Hebrew University of Jerusalem: Comprehensive study shows major ongoing decline in sperm counts of Western men, pointing to improved male health and declining fertility.
28.07.2017