Hagai Levine1,2, Niels Jørgensen3, Anderson Martino-Andrade2,4, Jaime Mendiola5, Dan Weksler-Derri6, Irina Mindlis7, Rachel Pinotti8, Shanna H Swan7. 1. Braun School of Public Health and Community Medicine, Hadassah-Hebrew University, the Hebrew University Center of Excellence in Agriculture and Environmental Health, Ein Kerem Campus, PO BOX 12272, Jerusalem 9110202, Israel. 2. Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 3. University Department of Growth and Reproduction, University of Copenhagen, Rigshospitalet, CopenhagenDK-2100, Denmark. 4. Department of Physiology, Federal University of Parana, Curitiba 81531-980, Brazil. 5. Division of Preventive Medicine and Public Health, University of Murcia School of Medicine and Biomedical Research Institute of Murcia (IMIB-Arrixaca-UMU), Murcia30100, Spain. 6. Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva6676814, Israel. 7. Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY10029, USA. 8. Gustave L. and Janet W. Levy Library, Icahn School of Medicine at Mount Sinai, New York, NY10029, USA.
Abstract
BACKGROUND: Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis 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 pre-determined 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.
BACKGROUND: Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis 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 pre-determined 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.
Authors: Haotian Wu; Alexandra M Huffman; Brian W Whitcomb; Srinihaari Josyula; Suzanne Labrie; Ellen Tougias; Tayyab Rahil; Cynthia K Sites; Jonathan Richard Pilsner Journal: Reprod Biomed Online Date: 2018-11-16 Impact factor: 3.828
Authors: Feiby L Nassan; Jorge E Chavarro; Lidia Mínguez-Alarcón; Paige L Williams; Cigdem Tanrikut; Jennifer B Ford; Ramace Dadd; Melissa J Perry; Russ Hauser; Audrey J Gaskins Journal: Int J Hyg Environ Health Date: 2018-05-22 Impact factor: 5.840
Authors: Rossella Cannarella; Carmelo Liuzzo; Laura M Mongioì; Rosita A Condorelli; Sandro La Vignera; Salvatore Bellanca; Aldo E Calogero Journal: Environ Sci Pollut Res Int Date: 2019-08-31 Impact factor: 4.223
Authors: Ramy Abou Ghayda; Paige L Williams; Jorge E Chavarro; Jennifer B Ford; Irene Souter; Antonia M Calafat; Russ Hauser; Lidia Mínguez-Alarcón Journal: Environ Int Date: 2019-07-31 Impact factor: 9.621
Authors: Ana Cutillas-Tolín; Evdochia Adoamnei; Eva M Navarrete-Muñoz; Jesús Vioque; Miriam Moñino-García; Niels Jørgensen; Jorge E Chavarro; Jaime Mendiola; Alberto M Torres-Cantero Journal: Hum Reprod Date: 2019-10-02 Impact factor: 6.918