Sperm counts in Asian men: Reviewing the trend of past 50 years
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Objective: To reveal the trend in alterations of sperm counts in Asian men over the past 50 years. Methods: This study reviewed all the published reports to unveil the specific pattern of alterations of sperm concentrations in Asian men from 1965 till 2015. The time-related changes in sperm concentration were studied using linear regression analyses. Results: The present study elucidated the trend using the reports from Carlsen et al (1965-1990) and non-Carlsen studies published until 2015, on fertile Asian men. In the reports of Carlsen et al, no overall declining trend in Asian men (r = 0.509, P = 0.760) was observed during this tenure, but non-Carsen reports showed a significant time-dependent decline of sperm concentration (r =-0.754, P = 0.005) in Asian men. This present review also showed a mild time-dependant decline in sperm concentration (-0.44×10 6 /mL/year, 95% CI:-0.65 to-0.23; r =-0.473, P = 0.040) which accounted for an overall 22.17% decrease in past 50 years. Conclusions: This study brings to the forefront that sperm concentration among Asian men follows a mild declining trend over the period of 50 years, and further studies addressing the causes of this decline are required.