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=== Men === | === Men === | ||
In various Western and Non-Western countries, serum testosterone levels in males have declined substantially in the past century.<ref>https://pubmed.ncbi.nlm.nih.gov/17062768/</ref> Today, U.S. men have 30% lower T levels compared to 1987, affecting all age groups similarly.<ref>https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-the-man-your-father-was/</ref><ref>https://www.healio.com/endocrinology/hormone-therapy/news/print/endocrine-today/%7Bac23497d-f1ed-4278-bbd2-92bb1e552e3a%7D/generational-decline-in-testosterone-levels-observed</ref> | In various Western and Non-Western countries, serum testosterone (T) levels in males have declined substantially in the past century.<ref>https://pubmed.ncbi.nlm.nih.gov/17062768/</ref> Today, U.S. men have 30% lower T-levels compared to 1987, affecting all age groups similarly.<ref>https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-the-man-your-father-was/</ref><ref>https://www.healio.com/endocrinology/hormone-therapy/news/print/endocrine-today/%7Bac23497d-f1ed-4278-bbd2-92bb1e552e3a%7D/generational-decline-in-testosterone-levels-observed</ref> | ||
Similarly, a Danish study found male cohorts born in the 1960s have on average 14 percent lower testosterone levels than males from the 1920s.<ref>https://academic.oup.com/jcem/article/92/12/4696/2597312</ref> An Israeli study found a similar secular decline as well.<ref>Chodick, G., Epstein, S., & Shalev, V. (2020). Secular trends in testosterone- findings from a large state-mandate care provider. Reproductive Biology and Endocrinology, 18(1). doi:10.1186/s12958-020-00575-2 </ref> Testosterone supplement prescriptions have doubled from 2010 to 2013 in the U.S.<ref>http://jamanetwork.com/journals/jama/article-abstract/2612615</ref> In a study from 2018, 409 male students a staggering 35% met the criteria for androgen deficiency based on a survey instrument designed to assess older males,<ref name="charlier2018">https://www.mdpi.com/2227-9032/6/4/121</ref> and the score on this survey instrument significantly correlated with stress levels and poor sleep quality, which are considered symptoms of androgen deficiency. | Similarly, a Danish study found male cohorts born in the 1960s have on average 14 percent lower testosterone levels than males from the 1920s.<ref>https://academic.oup.com/jcem/article/92/12/4696/2597312</ref> An Israeli study found a similar secular decline as well.<ref>Chodick, G., Epstein, S., & Shalev, V. (2020). Secular trends in testosterone- findings from a large state-mandate care provider. Reproductive Biology and Endocrinology, 18(1). doi:10.1186/s12958-020-00575-2 </ref> Testosterone supplement prescriptions have doubled from 2010 to 2013 in the U.S.<ref>http://jamanetwork.com/journals/jama/article-abstract/2612615</ref> In a study from 2018, 409 male students a staggering 35% met the criteria for androgen deficiency based on a survey instrument designed to assess older males,<ref name="charlier2018">https://www.mdpi.com/2227-9032/6/4/121</ref> and the score on this survey instrument significantly correlated with stress levels and poor sleep quality, which are considered symptoms of androgen deficiency. It remains, however, unclear to which extent a decline in T is related to a feminization of the entire phenotype as the male body is able to adapt to changing levels in T (see [[Testosterone#Secular_decline_in_T-levels_of_Western_men|testosterone]]). | ||
Some of | Some of the trend in T-levels can be attributed the aging population due to older males exhibiting lower testosterone levels. Various comorbidities, including diabetes and obesity are known to decrease testosterone levels, and these conditions have become more prevalent over time.<ref>https://www.urologytimes.com/view/testosterone-levels-show-steady-decrease-among-young-us-men</ref><ref>J Clin Endocrinol Metab. 2006:doi10.1210/jc.2006-1859</ref> But even after controlling for confounders like age, race, BMI and comorbidities, alcohol consumption, smoking, and physical activity, total T-level still decreased highly significantly (p < 0.0001) from 605.39 ng/dL 1999-2000, 567.44 ng/dL in 2003-2004, 424.96 ng/dL in 2011-2012, 431.76 ng/dL in 2013-2014, to 451.22 ng/dL in 2015-2016, with average levels declining by about 1% per year. Obesity has been specifically ruled out as a sufficient primary explanation for the trend.<ref>https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076178</ref> | ||
The sperm count in Western men has also dropped dramatically with today's men's ejaculate only yielding roughly half of the sperm counts compared to 1973,<ref>https://www.nytimes.com/2017/08/16/health/male-sperm-count-problem.html</ref> leading to a greater incidence of infertility among those younger than 30 (today's fertility is 15% lower than 1980s levels).<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3253726/</ref> Sperm count appears to be related to | The sperm count in Western men has also dropped dramatically with today's men's ejaculate only yielding roughly half of the sperm counts compared to 1973,<ref>https://www.nytimes.com/2017/08/16/health/male-sperm-count-problem.html</ref> leading to a greater incidence of infertility among those younger than 30 (today's fertility is 15% lower than 1980s levels).<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3253726/</ref> Sperm count appears to be related to fertility,<ref>https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2605.1982.tb00255.x</ref> and compared to the 1920s when around 17% of women were in the subfertile range of sperm count, today around 40% of men fulfill this criterion.<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3343360/</ref> | ||
Paralleling this decline in human sperm, dog semen quality has also seen degradation in some areas.<ref name="lea016">https://www.nature.com/articles/srep31281</ref> | Paralleling this decline in human sperm, dog semen quality has also seen degradation in some areas.<ref name="lea016">https://www.nature.com/articles/srep31281</ref> | ||
Milennials also have weaker grip strength compared to 1985,<ref>https://www.npr.org/sections/health-shots/2016/06/13/481590997/millennials-may-be-losing-their-grip</ref> though with more obvious causes of sedentary lifestyle and computer-related work | Milennials also have weaker grip strength compared to 1985,<ref>https://www.npr.org/sections/health-shots/2016/06/13/481590997/millennials-may-be-losing-their-grip</ref> though with more obvious causes of sedentary lifestyle and computer-related work as evidenced by women's grip strength also declining, although less signficantly, with women aged 30-34 even seeing an increase. There has also been a secular decline in grip strength both among athletes,<ref>https://www.sciencedirect.com/science/article/pii/S1728869X19300085</ref> as well as a decline in overall sekeltal muscle strength.<ref>https://www.washingtonpost.com/news/wonk/wp/2016/08/15/todays-men-are-nowhere-near-as-strong-as-their-dads-were-researchers-say/</ref> | ||
Corroborating these secular trends at the physiological and physical level, one can also observe feminization trends at the psychological and behavioral level. For example, there has been a heightened incidence of depression in the U.S. between 2005 and 2015, with women being generally more likely diagnosed with mood disorders (implying these are a sexually dimorphic mental disorders).<ref name="wein2017">Weinberger, A. H., Gbedemah, M., Martinez, A. M., Nash, D., Galea, S., & Goodwin, R. D. (2017). Trends in depression prevalence in the USA from 2005 to 2015: widening disparities in vulnerable groups. Psychological Medicine, 48(08), 1308–1315. doi:10.1017/s0033291717002781</ref> | Corroborating these secular trends at the physiological and physical level, one can also observe feminization trends at the psychological and behavioral level. For example, there has been a heightened incidence of depression in the U.S. between 2005 and 2015, with women being generally more likely diagnosed with mood disorders (implying these are a sexually dimorphic mental disorders).<ref name="wein2017">Weinberger, A. H., Gbedemah, M., Martinez, A. M., Nash, D., Galea, S., & Goodwin, R. D. (2017). Trends in depression prevalence in the USA from 2005 to 2015: widening disparities in vulnerable groups. Psychological Medicine, 48(08), 1308–1315. doi:10.1017/s0033291717002781</ref> | ||