Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries

UnHope20 · 2022-11-18T06:16:35+00:00

I don't know why this was reported as misinformation but sharing a scientific report/meta-analysis that was published in a peer-reviewed journal is anything but misinformation.

The topic of this study has been posted about in this community on several occasions. See here, here and here for reference.

Based on the fact that this post received 2 two reports of the same nature (Unsubstantiated claims) I am going to tell whomever is trying to clandestine brigade this content to call it quits before you get reported to Reddit HQ.

This post doesn't any violate rules and will remain up until further notice.

Stickying post for 1 week.

shit-zen-giggles · 2022-11-16T22:41:18+00:00

BACKGROUND

Numerous studies have reported declines in semen quality and other markers of male reproductive health. Our previous meta-analysis reported a significant decrease in sperm concentration (SC) and total sperm count (TSC) among men from North America–Europe–Australia (NEA) based on studies published during 1981–2013. At that time, there were too few studies with data from South/Central America–Asia–Africa (SAA) to reliably estimate trends among men from these continents.

OBJECTIVE AND RATIONALE

The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis and the controversies surrounding this issue warranted an up-to-date meta-analysis.

SEARCH METHODS

We searched PubMed/MEDLINE and EMBASE to identify studies of human SC and TSC published during 2014–2019. After review of 2936 abstracts and 868 full articles, 44 estimates of SC and TSC from 38 studies met the protocol criteria. Data were extracted on semen parameters (SC, TSC, semen volume), collection year and covariates. Combining these new data with data from our previous meta-analysis, the current meta-analysis includes results from 223 studies, yielding 288 estimates based on semen samples collected 1973–2018. Slopes of SC and TSC were estimated as functions of sample collection year using simple linear regression as well as weighted meta-regression. The latter models were adjusted for predetermined covariates and examined for modification by fertility status (unselected by fertility versus fertile), and by two groups of continents: NEA and SAA. These analyses were repeated for data collected post-2000. Multiple sensitivity analyses were conducted to examine assumptions, including linearity.

OUTCOMES

Overall, SC declined appreciably between 1973 and 2018 (slope in the simple linear model: –0.87 million/ml/year, 95% CI: –0.89 to –0.86; P < 0.001). In an adjusted meta-regression model, which included two interaction terms [time × fertility group (P = 0.012) and time × continents (P = 0.058)], declines were seen among unselected men from NEA (–1.27; –1.78 to –0.77; P < 0.001) and unselected men from SAA (–0.65; –1.29 to –0.01; P = 0.045) and fertile men from NEA (–0.50; –1.00 to –0.01; P = 0.046). Among unselected men from all continents, the mean SC declined by 51.6% between 1973 and 2018 (–1.17: –1.66 to –0.68; P < 0.001). The slope for SC among unselected men was steeper in a model restricted to post-2000 data (–1.73: –3.23 to –0.24; P = 0.024) and the percent decline per year doubled, increasing from 1.16% post-1972 to 2.64% post-2000. Results were similar for TSC, with a 62.3% overall decline among unselected men (–4.70 million/year; –6.56 to –2.83; P < 0.001) in the adjusted meta-regression model. All results changed only minimally in multiple sensitivity analyses.

WIDER IMPLICATIONS

This analysis is the first to report a decline in sperm count among unselected men from South/Central America–Asia–Africa, in contrast to our previous meta-analysis that was underpowered to examine those continents. Furthermore, data suggest that this world-wide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed.

Title	Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries
Author	shit-zen-giggles
Upvotes	12
Comments	3
Date	November 16, 2022 10:40 PM UTC (3 years ago)
Subreddit	Posted in /r/Male_Studies
Original Link	https://old.reddit.com/r/Male_Studies/comments/yx8ntc/temporal_trends_in_sperm_count_a_systematic/
Archive Link	https://theredarchive.com/r/Male_Studies/temporal-trends-in-sperm-count-a-systematic-review.1215710 https://theredarchive.com/post/1215710

Comments

BACKGROUND

OBJECTIVE AND RATIONALE

SEARCH METHODS

OUTCOMES

WIDER IMPLICATIONS