Trend of change of sperm count and concentration over the last two decades: A systematic review and meta‐regression analysis

Abstract

AbstractBackgroundSince the 1970s, several studies found that sperm concentration (SC) and total sperm count (TSC) constantly worsened over time, mainly in high‐income countries.ObjectivesTo evaluate whether the decreasing trend in sperm count is continuing in Western European countries and USA, we performed a systematic review and meta‐regression analysis.Materials and methodsEmbase and Pubmed/Medline were searched papers published in English in the 2000–2020 period limiting the search to data collected in the USA and Western European countries.ResultsWe identified 62 articles and pooled information on 24,196 men (range 10–2,523), collected from 1993 to 2018. Considering all the studies, random‐effects meta‐regression analyses showed no significant trend for SC (slope per year −0.07 mil/mL, p‐value = 0.86). Negative trends of SC were detected in Scandinavian countries (slope per year −1.11 mil/mL, 95% CI: −2.40 to +0.19; p‐value = 0.09), but the findings were statistically not significant. No significant trends of SC were detected in Central Europe (slope per year +0.23, 95% CI −2.51 to +2.96; p‐value = 0.87), the USA (slope per year +1.08, 95% CI −0.42 to +2.57; p‐value = 0.16), and Southern Europe (slope per year +0.19, 95% CI −0.99 to +1.37; p‐value = 0.75).We have analyzed separately findings from studies including sperm donors, fertile men, young unselected men (unselected men, study mean age < 25 years) and unselected men (unselected men, study mean age ≥ 25 years). No significant trends of SC were observed among sperm donors (slope per year −2.80, 95% CI −6.76 to +1.17; p‐value 0.16), unselected men (slope per year −0.23, 95% CI −1.58 to +1.12; p‐value 0.73), young unselected men (slope per year −0.49, 95% CI −1.76 to +0.79; p‐value 0.45), fertile men (slope per year +0.29, 95% CI −1.09 to +1.67; p‐value 0.68).Discussion and conclusionThe results of this analysis show no significant trends in SC, in USA, and selected Western European countries.