Sci will go ahead and put it out there: she hates smoking (I mean tobacco). It's gross. It smells. You NEVER get that freakin' smell out of your hair. And your teeth get all nasty. Not to mention to horrendous side effects, things like cancer and cardiovascular problems and death...yeah, those are bad, too.
So anyway, I think we all know smoking is bad for you. Addictive, cancer-causing, the addictive part is particularly bad, nicotine has an extremely high number of reinforcers obtained per drug session (you can only take one line of cocaine at a time, really, but a cigarette has you occupied, puffing away for a good few minutes). But now men have ANOTHER reason not to smoke: your little swimmers don't like it.
Kumosani, et al. "The influence of smoking on semen quality, seminal microelements, and Ca2+-ATPase activity among infertile and fertile men." Clinical Biochemistry, 2008.
(teehee, via softpedia)
I'm not sure why so many of these male fertility studies are done in the Middle East. This one's from Saudi Arabia. I don't think there's a higher rate of fertility concerns...
So what about smoking causes problems with sperm? Well, it can be tough to tell. There are a LOT of chemicals in cigarettes, estimates are over 4000 chemicals, about 40 of which can cause cancer (Bernhard, 2005). Interestingly to researchers, some of these chemicals are heavy metals such as cadmium, which is associated with problems in the respiratory tract, as well as being associated with male infertility.
Cadmium is known to disrupt spermatogenesis, and it's thought that this might be through messing with essential elements such as calcium, magnesium, and zinc. Calcium is particularly important, it's one of the biggest regulators of sperm motility, and an increase in calcium is absolutely necessary to cause the sperm to release its acrosomal packet when it hits the egg (as seen here). Without that rise in calcium, the sperm will never relase enzymes to get through to the egg, and the magic will never happen. Calcium also has important roles in formation of sperm, so it's really very essential. So if you've got a lot of cadmium, and cadmium messes with calcium...that might be a hypothesis right there (though of course you can't rule out the other 4000 chemicals involved).
Cadmium ALSO messes with zinc, which also messes with calcium, so there's a possible secondary route there.
So the investigators wanted to know how smoking affected male fertility (measured in the number of sperm and their percent motility), and whether or not the changes in fertility were correlated with levels of cadmium in the seminal fluid. They took a bunch of guys coming in for fertility workups, and tested the ejaculate after they had refrained from sexual activity for three days.
And...yet again, they use TABLES. TABLES?!!??! ARGH!!!
Sci has ranted against tables before. She's going to have to do it again. Tables, they look CRAPPY. You have to go through and underline all the time. And then you have to figure out what the heck each line corresponds to, and the lines are only peripherally related, and ARGH MY EYES!!!
So, to save your pretty little eyes (so you can read lots of Neurotopia, which I'm sure is all you do in your spare time), Sci is going to stay up late and graph for you. I do it out of love.
You see why you should graph? Numbers are nice, but that figure is STRIKING. And yes, that difference between fertile and infertile men in sperm count is very significant. I also checked for a significant difference between the infertile smokers and infertile nonsmokers, p=0.07.
But this doesn't really tell us much. Mostly what it tells us is that infertile men tend to have very low sperm counts compared to fertile men, which is something we already knew (this is the case in many cases where a man is having fertility issues, but not in all cases).
This graph also has impressive significant between infertile and fertile men, but this is also something we knew from before. Infertile men often not only have decreased sperm count, they ALSO have decreased sperm motility. But Sci was a little surprised to learn that "normal" sperm motility was still only around 41%. You call that efficiency?
But here we get to the interesting stuff.
You can see that the Cadmium levels in the smokers are very high (p<0.01 smokers compared to nonsmokers). And that's not all:
(You see, Authors? If you had just graphed your own data, you wouldn't have to put up with Sci's blinding color choices. But now you DO! HA HA HA!!!!)
Not only are Cadmium levels high, but zinc levels are LOW (p<0.01 smokers vs nonsmokers). As cadmium is known to decrease zinc levels, this isn't particularly surprising.
Unfortunately, calcium levels did not differ. But the authors did include ONE graph. And it's an important one:
This figure showing the activity of the Ca2+-ATPase, a big indicator of membrane function in spermatozoa. And you can see that both fertile and infertile smokers show vast decreases in the activity of the ATPase. This implies that membrane function could be compromised as a result of smoking, and their other data shows that there is a correlation between smoking, decreased Ca2+-ATPase activity, low levels of zinc, and high levels of cadmium. From this, the authors believe that cadmium is the cause of all these troubles in the sperm.
Sci thinks this is a good study on the effects of smoking on fertility parameters, but she would hesitate to go the distance with the authors here. There is certainly a correlation between the high levels of cadmium, the decreased zinc, and the decreased ATPase activity, but Sci wants a little more proof. The best possible thing would be to lower the cadmium levels, and see a resulting increase in zinc and ATPase activity (and possibly in function fertility, though I doubt it). The best way to do this would be to take smokers and measure before and after quitting to see if levels recover, though you could more easily do the study in animals by artificially increasing and decreasing levels of cadmium. This second choice would actually be the more "pure" study, as it would rule out the slew of other chemical associated with smoking and show that it is indeed the cadmium, and nothing else, that is responsible for the effects.
Still, the study has interesting correlations, if not causations. So while smoking may not be the be-all, end all of fertility in men, it appears that it can only hurt, not help. Another good reason not to start smoking.
KUMOSANI, T., ELSHAL, M., ALJONAID, A., & ABDULJABAR, H. (2008). The influence of smoking on semen quality, seminal microelements and Ca2+-ATPase activity among infertile and fertile men Clinical Biochemistry, 41 (14-15), 1199-1203 DOI: 10.1016/j.clinbiochem.2008.07.013