December 5, 2012

expert reaction to research into number and quality of sperm

Research in the journal Human Reproduction suggested that the concentration and quality of sperm  in a sample of 26,600 French men has been in steady decline between 1989 and 2005. 

Dr. Allan Pacey, Senior Lecturer in Andrology, University of Sheffield, said:

“There have been numerous studies published over the past 20 years which have claimed to show that human semen quality (measured by either sperm count, motility or morphology) could have decreased over time. Yet others have been published which have shown no change. As such, a very unclear picture has been painted about whether semen quality has actually changed and importantly whether or not we should be worried about any environmental threats to male fertility.

“Unfortunately, almost all of the studies published to date have inevitable flaws of one type or another. This is usually because they rely on piecing together historical data, or because the men were recruited to them were not representative of the general population (i.e. they were patients at fertility clinics, men having vasectomy, or men recruited as potential sperm donors). Therefore, getting a clear picture of what may have happened in the general population has been extremely difficult and I would argue that the ‘jury is still out’ on this issue.

“This paper is an impressive attempt at dealing with many of the previous criticisms by looking at the semen quality of men undergoing IVF or ICSI treatment with women with absent or blocked Fallopian tubes. Experimentally, this is a close approximation to what we might expect to see in men from the general population but without the many pitfalls and expense of trying to recruit them to a study. Moreover, the statistical approach used in this paper appears to be very elegant, although it is very disappointing that the authors could not control for socioeconomic status, since we already know that this has a major impact on semen quality.

“What is disappointing to me about the paper is that the authors provide too few details about the laboratory methods used to measure sperm concentration and motility. In the paper, the authors claim that the methods for measurement of sperm concentration and motility ‘have not changed noticeably during the study period’ yet to me this is an odd thing to say as in my experience they have changed remarkably everywhere else in the world! There have been two revisions of International Guidelines published by the World Health Organisation between 1989 and 2005, as well as increasing emphasis on quality control and quality assurances procedures that were rarely performed 20 years ago as part of general improvement in quality management systems. Therefore, I am left questioning how much of the changes described in this paper are simply a function of alterations to laboratory method.

“With regard to the measurement of sperm morphology, the authors quite rightly point out that it is a difficult procedure to perform and seem to acknowledge that definition changes may account for much of their observed decrease. However, they report unfeasibly high values for percent morphology in the order of 60.9% in 1989 to 52.8% in 1995. This is significantly out of step with my professional experience and my role as chair of the steering group for our UK national quality control programme for andrology. I simply don’t understand this data and how they have made these measurements and whether they are robust!

“There is no doubt that this paper is a useful contribution to the literature, but I would urge much caution in its interpretation as there remains too many unknowns. In my view, the paper certainly does not resolve the issue of whether or not sperm counts have declined or not. If we were to believe the data uncritically, we should put the changes into clinical context: the change in sperm concentration described 73.6 to 49.9 million per ml is still well within the normal range and above the lower threshold of concern used by doctors which is suggestive of male infertility (15 million per ml).

“In spite of my obvious criticisms of this paper, I think there remains a need to be vigilant on this topic and I would support the authors conclusions about the need for gamete quality monitoring systems. However, these need to be designed robustly if we are ever going to answer this important question.”

Prof Richard Sharpe, MRC Centre for Reproductive Health, University of Edinburgh, said:

“Background: The concept that sperm counts have declined with time because of environmental/lifestyle impacts is not new, but has remained controversial. This has been mainly because comparing data for sperm counts from different centres in different time periods (eg in the 1970s with the present) always leaves room for doubt as to whether the decrease is genuine or has another explanation, and of course we cannot go back in time and check the earlier data.

“Another huge obstacle to studying changes across time in sperm counts is that, in general, it is only men with fertility problems who get to have their sperm counts checked, and sperm counts in these men will be lower than in men from the general population. So, finding out what is happening to sperm counts in ‘normal’ men from the general population is not easy.

“Strengths of this study: The present study has essentially sidestepped both of the above issues by (1) studying men evaluated in a standard setting (ART centres) in one country over a 17-year period, and (2) including only men whose partners were proven to be the cause of couple infertility. It is a hugely impressive study, and for numbers (26,600 men), dwarfs previous studies and gives it immense power.

“The key findings: The take-home message from the study is extremely simple, sperm number and sperm quality has declined progressively over the study period. For example, sperm count decreased by 32.2%. As the men studied are likely to be representative of the general population, this confirms that sperm counts have/are falling and essentially dispels the previous controversy described above. It also fits with studies across Europe in young men, which show that 1 in 5 have a sperm count low enough to impair fertility

“The implications: These findings have two population-wide health implications, (1) the impact on couple fertility, (2) the environmental/lifestyle factors that have caused the fall in sperm counts/quality.

(1) Fertility is a couple issue. If men have lower sperm counts it can place more emphasis on the need for high fertility in their female partner. However, because most couples are now delaying trying for children until in their 30s, this occurs when female fertility is on the decline (at 30-35 years it is only 40-50% of what it is at 20-25 years; see Sharpe 2012 EMBO Reports). This, combined with decreasing sperm counts in their male partner, leads to only one outcome – more couples are going to be experiencing fertility problems.

(2) The decrease in sperm counts year on year shown in this study, demonstrates that something(s) in our modern lifestyle, diet or environment (eg chemical exposures) is causing this, and it is getting progressively worse. We still do not know which are the most important factors, but perhaps the most likely is that it is a combination (‘double whammy’) of changes such as a high fat diet combined with increased environmental chemical exposures.

“What should be done: There are two key issues. First, identification of what factors in our diet, lifestyles and/or environment are responsible for falling sperm counts. Second, when do these factors act, because there is a growing body of evidence that falling sperm counts my stem from effects via the mother during pregnancy. However, effects in adult life are also increasingly indicated (eg due to diet).

“Armed with such knowledge, we can potentially prevent or reverse the adverse changes in sperm counts; without it, we have to expect that sperm counts will continue to decrease. In the UK this issue has never been viewed as any sort of health priority, perhaps because of doubts as to whether ‘falling sperm counts’ was real. Now, there can be little doubt that it is real, so it is a time for action. Doing nothing will ensure that couple fertility and average family size will decline below even its present low level and place ever greater strains on society (eg by reducing numbers of tax-payers; for fuller details see Sharpe 2012 EMBO Reports).”

‘Decline in semen concentration and morphology in a sample of 26 609 men close to general population between 1989 and 2005 in France’, by Rolland et al. (doi:10.1093/humrep/des415), published in Human Reproduction on Wednesday 5^th December.