Re: Sperm counts, testicular cancers, and the environment
In a society that seems to readily ignore issues with male fertility, be it through lack of scientific knowledge or simply masculine embarrassment, it was great for this week’s print editorial to highlight the topic. [1] However, the article has made a number of assumptions which lower the reliability of its conclusions. First is the idea the EDCs are the main cause of declining sperm quality, which has been pinpointed as flawed by some of the article’s responses, but also the suggestion that sperm quality is the only factor in declining total fertility rates (TFR). This means the article exaggerates the effects of poor sperm quality in the present day.
The meta-analysis by Levine shows that total sperm count (TSC) and sperm concentration (SC) have declined since 1973. [2] As an overall trend this is correct, yet it is far from the whole picture. It should be noted, for starters, that these data were collected from a huge number of studies over the period of 1973-2011. Many samples were taken from fertility clinics, where sperm quality amongst male visitors is already low enough for them to be seeking help with conception. Growth in abundance of these fertility clinics has caused a steady increase in data available from such establishments, leading to a skewed view of sperm quality in the overall population as the ratio of known low sperm quality samples to other available samples has got larger over time. In fact, primary data collected for the sole purposes of studying declining sperm quality has concluded that both TSC and SC are increasing in the young population. [3]
Furthermore, even though the Levine analysis reveals a decline in sperm quality over the past 44 years, it also shows that both TSC and SC are well above what the WHO consider to be a low sperm count. [4] Looking at the data the average TSC in recent studies is 4.7x10(7)/ml; when SC reaches 4.0x10(7)/ml the likelihood of conception stays roughly the same no matter how much greater the concentration gets. Many sufferers of oligospermia with half this concentration will go on to conceive naturally within two years anyway. [5]
Focussing on declining sperm quality therefore cannot be the way to deal with the falling fertility rate in the west. Instead of a “holistic view of male reproductive health problems”, a holistic view of every medical and environmental factor must be employed. Take Japan as an example. It is particularly interesting regarding this issue because the country has an aging population resulting from its low birth rate combined with the highest life expectancy in the world. [6] The population is living longer so there is no sense in urgency for marriage or conception as more time is available in a person’s lifetime for both.
On top of this, Japanese culture has incredibly traditional values. If a woman marries she is expected to bear children and then stay at home to care for them; styling life like this is not of great appeal to the current youth, so women are putting off marriage to instead spend time finding fulfilment in their careers and reaching professional success. This is shown in the decline in marriage rates and later marriages that correlate with an increase of females in the workforce. [7] More fertility treatments and options are also available for those who want to delay childbirth. The ability to freeze eggs is relatively new, but women are happy to pay for this so they can conceive beyond menopause and public funding is available for this procedure in some areas to try and combat the low birth rate. [8] There has in fact been a small climb in TFR in the past three years, probably due to the “tempo effect” whereby catch up occurs after an entire generation changes the average age they have their first child. [9]
A diminishing fertility rate is seen in all developed countries, though. In Europe no countries match the replacement rate of 2.1. Most western nations also fall below this, not necessarily because of disregard to traditional values but because of other local influences. Some simple examples of this follow. Fewer people are theists, meaning teachings about traditional family values are less apparent and the idea that sexual intercourse is for solely reproduction has lost its hold. Sex education is now a prominent part of childhood learning and people know about the methods of contraception available, all of which are easily accessible in developed countries. Cost of raising a child has also gone up meaning would-be parents are put off having more than one child, if any at all.
It’s important not to overlook statistics showing declining TSC and SC, and more research should be done surrounding low sperm quality and it’s causes to prevent any future decline, but it is currently not as large an issue as has been made out. Fertility rates below the replacement rate is the problem the western world currently faces but this cannot be tackled from a purely medical stand point. Cultural aspects of life currently have the greatest influence on TFR, and these mentalities are very hard to change as they are embedded into entire generations. (At the same time the world must be wary. Whilst developed nations do have a low birthing rate, the world currently averages out at 2.5, as some countries reach heights of 7.6. [10])
Whilst it is hard, nigh on impossible, to give a definitive cause for low TFR in western countries, what can be said for certain is this. Sperm quality is not the main cause of low fertility in the developed world, and the only way we can begin to tackle extreme shortfall from the replacement rate across different countries is to consider everywhere individually and target resolutions to each area based off all cultural and scientific data to hand.
1. Skakkebaek Niels E. Sperm counts, testicular cancers, and the environment BMJ 2017; 359 :j4517
2. Hagai Levine, Niels Jørgensen, Anderson Martino-Andrade, Jaime Mendiola, Dan Weksler-Derri, Irina Mindlis, Rachel Pinotti, Shanna H Swan; Temporal trends in sperm count: a systematic review and meta-regression analysis, Human Reproduction Update, Volume 23, Issue 6, 1 November 2017, Pages 646–659, https://doi.org/10.1093/humupd/dmx022
3. Jørgensen N, Joensen UN, Jensen TK, et al; Human semen quality in the new millennium: a prospective cross-sectional population-based study of 4867 men, BMJ Open 2012;2:e000990. doi:10.1136/bmjopen-2012-000990
4. Cooper TG, Noonan E, von Eckardstein S, et al. (2010). "World Health Organization reference values for human semen characteristics". Hum. Reprod. Update. 16 (3): 231–45. PMID 19934213. doi:10.1093/humupd/dmp048.
5. Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners. Bonde, Jens Peter EHenriksen, Tine Brink et al. The Lancet , Volume 352 , Issue 9135 , 1172 – 1177
6.http://www.who.int/gho/publications/world_health_statistics/2016/EN_WHS2...
7. Ministry of Internal Affairs and Communication, Statistics Bureau. "Japan Statistical Yearbook, Chapter 2: Population and Households".
8. http://www.bbc.co.uk/news/world-asia-36551807
9. Harding, Robin (4 February 2016). "Japan birth rate recovery questioned". Financial Times. Retrieved 21 February 2016.
10. https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?
Rapid Response:
Re: Sperm counts, testicular cancers, and the environment
In a society that seems to readily ignore issues with male fertility, be it through lack of scientific knowledge or simply masculine embarrassment, it was great for this week’s print editorial to highlight the topic. [1] However, the article has made a number of assumptions which lower the reliability of its conclusions. First is the idea the EDCs are the main cause of declining sperm quality, which has been pinpointed as flawed by some of the article’s responses, but also the suggestion that sperm quality is the only factor in declining total fertility rates (TFR). This means the article exaggerates the effects of poor sperm quality in the present day.
The meta-analysis by Levine shows that total sperm count (TSC) and sperm concentration (SC) have declined since 1973. [2] As an overall trend this is correct, yet it is far from the whole picture. It should be noted, for starters, that these data were collected from a huge number of studies over the period of 1973-2011. Many samples were taken from fertility clinics, where sperm quality amongst male visitors is already low enough for them to be seeking help with conception. Growth in abundance of these fertility clinics has caused a steady increase in data available from such establishments, leading to a skewed view of sperm quality in the overall population as the ratio of known low sperm quality samples to other available samples has got larger over time. In fact, primary data collected for the sole purposes of studying declining sperm quality has concluded that both TSC and SC are increasing in the young population. [3]
Furthermore, even though the Levine analysis reveals a decline in sperm quality over the past 44 years, it also shows that both TSC and SC are well above what the WHO consider to be a low sperm count. [4] Looking at the data the average TSC in recent studies is 4.7x10(7)/ml; when SC reaches 4.0x10(7)/ml the likelihood of conception stays roughly the same no matter how much greater the concentration gets. Many sufferers of oligospermia with half this concentration will go on to conceive naturally within two years anyway. [5]
Focussing on declining sperm quality therefore cannot be the way to deal with the falling fertility rate in the west. Instead of a “holistic view of male reproductive health problems”, a holistic view of every medical and environmental factor must be employed. Take Japan as an example. It is particularly interesting regarding this issue because the country has an aging population resulting from its low birth rate combined with the highest life expectancy in the world. [6] The population is living longer so there is no sense in urgency for marriage or conception as more time is available in a person’s lifetime for both.
On top of this, Japanese culture has incredibly traditional values. If a woman marries she is expected to bear children and then stay at home to care for them; styling life like this is not of great appeal to the current youth, so women are putting off marriage to instead spend time finding fulfilment in their careers and reaching professional success. This is shown in the decline in marriage rates and later marriages that correlate with an increase of females in the workforce. [7] More fertility treatments and options are also available for those who want to delay childbirth. The ability to freeze eggs is relatively new, but women are happy to pay for this so they can conceive beyond menopause and public funding is available for this procedure in some areas to try and combat the low birth rate. [8] There has in fact been a small climb in TFR in the past three years, probably due to the “tempo effect” whereby catch up occurs after an entire generation changes the average age they have their first child. [9]
A diminishing fertility rate is seen in all developed countries, though. In Europe no countries match the replacement rate of 2.1. Most western nations also fall below this, not necessarily because of disregard to traditional values but because of other local influences. Some simple examples of this follow. Fewer people are theists, meaning teachings about traditional family values are less apparent and the idea that sexual intercourse is for solely reproduction has lost its hold. Sex education is now a prominent part of childhood learning and people know about the methods of contraception available, all of which are easily accessible in developed countries. Cost of raising a child has also gone up meaning would-be parents are put off having more than one child, if any at all.
It’s important not to overlook statistics showing declining TSC and SC, and more research should be done surrounding low sperm quality and it’s causes to prevent any future decline, but it is currently not as large an issue as has been made out. Fertility rates below the replacement rate is the problem the western world currently faces but this cannot be tackled from a purely medical stand point. Cultural aspects of life currently have the greatest influence on TFR, and these mentalities are very hard to change as they are embedded into entire generations. (At the same time the world must be wary. Whilst developed nations do have a low birthing rate, the world currently averages out at 2.5, as some countries reach heights of 7.6. [10])
Whilst it is hard, nigh on impossible, to give a definitive cause for low TFR in western countries, what can be said for certain is this. Sperm quality is not the main cause of low fertility in the developed world, and the only way we can begin to tackle extreme shortfall from the replacement rate across different countries is to consider everywhere individually and target resolutions to each area based off all cultural and scientific data to hand.
1. Skakkebaek Niels E. Sperm counts, testicular cancers, and the environment BMJ 2017; 359 :j4517
2. Hagai Levine, Niels Jørgensen, Anderson Martino-Andrade, Jaime Mendiola, Dan Weksler-Derri, Irina Mindlis, Rachel Pinotti, Shanna H Swan; Temporal trends in sperm count: a systematic review and meta-regression analysis, Human Reproduction Update, Volume 23, Issue 6, 1 November 2017, Pages 646–659, https://doi.org/10.1093/humupd/dmx022
3. Jørgensen N, Joensen UN, Jensen TK, et al; Human semen quality in the new millennium: a prospective cross-sectional population-based study of 4867 men, BMJ Open 2012;2:e000990. doi:10.1136/bmjopen-2012-000990
4. Cooper TG, Noonan E, von Eckardstein S, et al. (2010). "World Health Organization reference values for human semen characteristics". Hum. Reprod. Update. 16 (3): 231–45. PMID 19934213. doi:10.1093/humupd/dmp048.
5. Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners. Bonde, Jens Peter EHenriksen, Tine Brink et al. The Lancet , Volume 352 , Issue 9135 , 1172 – 1177
6.http://www.who.int/gho/publications/world_health_statistics/2016/EN_WHS2...
7. Ministry of Internal Affairs and Communication, Statistics Bureau. "Japan Statistical Yearbook, Chapter 2: Population and Households".
8. http://www.bbc.co.uk/news/world-asia-36551807
9. Harding, Robin (4 February 2016). "Japan birth rate recovery questioned". Financial Times. Retrieved 21 February 2016.
10. https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?
Competing interests: No competing interests