Black men have lower sperm counts than white men

Semen parameters in fertile US men: the Study for Future Families

The Study for Future Families (SFF) recruited men who were partners of pregnant women attending prenatal clinics in Los Angeles CA, Minneapolis MN, Columbia MO, New York City NY and Iowa City IA. Semen samples were collected on site from 763 men (73% White, 15% Hispanic/Latino, 7% Black and 5% Asian or other ethnic group) using strict quality control and well-defined protocols. [. . .] Black men had significantly lower semen volume, sperm concentration and total motile sperm counts than White and Hispanic/Latino men.
This is consistent with the other evidence I'm aware of. Lower sperm counts have been noted in Africa, and a study in Rochester, NY, that included a small number of American blacks similarly found:
All sperm parameters were significantly lower in the small subgroup (n = 7) of African-American men compared with other men in this population (p-values for sperm parameters, < 0.001 to 0.016).
Also consistent with these results: the only autopsy studies I'm aware of (at least one of which Rushton knew of before he became selectively forgetful) both suggest black men have smaller/lighter testes than white men.

14 comments:

Peter Frost said...

I would be careful about drawing any conclusions. A sperm count will be lower if the man has ejaculated over the previous three days. Yes, the participants in this study were married men, but marriage doesn't preclude masturbation or sex with other women.

n/a said...

Peter,

I'm pretty sure blacks self-report less masturbation. That may or may not be partly attributable to greater social desirability bias in blacks, but either way there's still no evidence in the direction you suggest.

I also believe that going by surveys that ask when the last time someone had sex was (rather than directly asking someone how frequently they have sex), US black men if anything have sex less frequently than US white men.

Finally, I didn't "draw conclusions" in this post (if by that you mean proposing deep evolutionary explanations or ruling out any possible environmental influences). I just relayed some evidence, for the benefit of people who draw conclusions based on circularly-invented "facts" that have never actually been supported by the data, and people misled by them.

Anonymous said...

Similarly, a study in Italy found that Nothern Italian men belonging to paternal haplogroup E had a significantly higher rate of low sperm counts than men belonging to other haplogroups:

http://jmg.bmj.com/content/44/3/205.abstract

Peter Frost said...

I guess we're in agreement. If the black participants self-reported less masturbation than they had actually engaged in, their sperm counts should correspondingly be lower than is the case in reality, i.e., in the absence of sexual activity. This kind of self-report bias, plus the very small sample size, makes the finding worthless.

Sometimes, I feel the same way as you do about people I disagree with. By a happy coincidence, the other fellow is always the one who is misled and engages in fallacious reasoning. But it's still wrong to counter a false argument with bad data. A false argument should be countered with good data.

n/a said...

Peter,

"This kind of self-report bias"

No, we're not in agreement: there is no evidence whatsoever the data is biased in this fashion, or that if it were this would fully explain low black sperm counts (much less explain why black men have physically smaller testes).

You're of course free to continue trying to make up reasons to ignore data you don't like, in service of being able to continue spinning theories unburdened by evidence. I'll continue to post the actual data I come across.

Gottlieb said...

Ui ui nervous people in the room, I did not understand, blacks have smaller testicles??

7 people is a very low amount of sampling and the black race is quite diverse.

Anonymous said...

Gottlieb it's multiple studies...

> Semen samples were collected on site from 763 men (73% White, 15% Hispanic/Latino, 7% Black and 5% Asian or other ethnic group)

That's 53 Black dudes in this one.

Sean said...

"blacks have smaller testicles?"
Yes, they do.

The study was on "men who were partners of pregnant women". The partners of pregnant women have drops in testosterone I believe. Moreover. Black men who have close relationships with women attending prenatal clinics may be untypical of Black men in general, as may those agreeing to participate in studies (Tuskegee?) may be.

n/a said...

The black sample in the larger study actually contains 57 individuals, and we're not talking about a small difference here. Mean black sperm counts are barely over half white sperm counts. Black sperm counts were lower than white sperm counts at testing locations in 4 different states (CA, MN, MO, and IA; this study didn't include enough samples for NY to be broken out separately).

Note that abstinence time is higher (not lower) in the black sample.

In the independent, Rochester, NY, study, despite the presence of only 7 black individuals, the differences were large enough to have p-values well below 5%.

These are the facts. You're going to need to start working on better excuses.

Peter Frost said...

Perhaps I'm missing something, but all this seems to prove is that many of the African Americans masturbated during their abstinence period. Even if they had masturbated at the same rate as the other participants, we're still looking at a massive reduction in sample size.

A recent study on semen quality found that almost a third of the participants failed to comply with the abstinence period, i.e., they either masturbated or had sex with a woman.

http://www.ncbi.nlm.nih.gov/pubmed/15236990

N/a, I assume you're an academic, so please cut out the ad hominem stuff. It sucks.

n/a said...

People who expect to be taken seriously don't get to invent facts and then use them as reasons to ignore data.

What is in evidence: reported abstinence time is higher (not lower) in the black sample.

What is not in evidence: any indication that the black sample more frequently misreported abstinence time.


"The methods for collection and analyses of semen samples
were previously described (Brazil et al., 2004a). Men were asked
to observe a 2–5 day abstinence period and then provide semen
samples by masturbation at study clinics. Samples were not
rejected if a man deviated from the requested abstinence period
,
but for this analysis we arbitrarily excluded 34 men with very
short (<2 h) or very long (>240 h) reported abstinence times.
Almost all samples (95%) were analysed within 45 min of collection.
Most men (approximately 85%) provided two samples an
average of 24 days apart."

"Men were requested to observe a 2–5 day abstinence period before providing each semen sample. Prior to each of the 2 visits, which were approximately 3 weeks apart, we mailed instructions regarding specimen collection, including a schedule to assist the subject in timing his last ejaculation prior to the visit. At the time of the visit the importance of accurately reporting the actual abstinence period was stressed, and the men were assured that their sample would not be rejected if they deviated from the recommended abstinence protocol."
http://onlinelibrary.wiley.com/doi/10.2164/jandrol.107.002741/full

Gottlieb said...

Ooops, sorry, i really don't see with attention to this.
This study was realized in Brazil??

Realist said...

Blacks have sex way more often than whites so it's predictable they would have less sperm left.

Trevayne Metcalfe said...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440492/?report=classic


https://www.ncbi.nlm.nih.gov/pubmed/17062768/

The first report in the first link is mainly about the great decline In European reproductive health, as seen by the fact that many European men have very low sperm counts. Thougths?