Global sperm count dropped by 59 percent in 40 years – meta-analysis Aug 2017

Temporal trends in sperm count: a systematic review and meta-regression analysis

Human Reproduction Update, pp. 1–14, 2017,doi:10.1093/humupd/dmx022

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BACKGROUND: Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive metaanalysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.

OBJECTIVE AND RATIONALE: To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.

SEARCH METHODS: PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group (‘Unselected by fertility’ versus ‘Fertile’), geographic group (‘Western’, including North America, Europe Australia and New Zealand versus ‘Other’, including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for predetermined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.

OUTCOMES: SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models —0.70 million/ml/year; 95% CI: —0.72 to —0.69; P < 0.001; slope in adjusted meta-regression models = —0.64; —1.06 to —0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (—1.38; —2.02 to —0.74; P < 0.001) and among Fertile Western (—0.68; —1.31 to —0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (—5.33 million/year, —7.56 to —3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (—2.06 million/ml, —3.38 to —0.74; P = 0.004 and —8.12 million, — 13.73 to —2.51, P = 0.006, respectively).

WIDER IMPLICATIONS: This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

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New York Times Report on the study - Oct 2017

• ". . sperm counts declined by 50 to 60 percent over the 38-year period between 1973 and 2011"
• Men in the Middle East are being more open about the medical problem and are seeking IVF help
• No mention of Vitamin D

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191 citations of the study as of Sept 2018

• The reproductive capacity of men has declined significantly over the past 4 decades
  in Psychosomatic Medicine and General Practice
  "From 1973 to 2011 the total sperm icount n the ejaculate decreased by 59.3% and continues to decrease by 1.6% annually."
  "They have reviewed 2510 and selected 185 studies with best design for further analysis. Thus, covered 42,935 men and the period from 1973 to 2011."
• Editorial -Sperm counts, testicular cancers, and the environment TheBMJ
  PDF costs $37

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Total sperm counts in North America, Europe, Australia and New Zealand dropped by nearly 60 percent between 1973 and 2013 and there’s no evidence to suggest this downward trend is leveling off Mercola Sept 2018

• Barely mentions low Vitamin D as a possible cause
• Phthalates and other endocrine-disrupting chemicals such as bisphenol-A are estrogen mimickers,
• Scientists have also linked phthalate exposure to
  Attention deficit disorder, Breast cancer, Obesity, Type 2 diabetes, Lowered IQ, Autism spectrum disorder
  Neurodevelopmental issues, Behavioral issues, Imbalanced growth hormone, Liver cancer, Altered thyroid function, Miscarriage