Male factor infertility can be influenced by lifestyle decisions and here we’ll chronicle what the data offers. A word of caution, the quality of data in this field is poor. Many of the endpoints are based on whether the subject in question (e.g. obesity) impacts the semen analysis.
Why is that a problem? As we discussed in the lesson on the semen analysis, there’s not a perfect correlation between the quality of the semen analysis and a man’s ability to conceive. In fact, men are often still able to conceive naturally when a semen analysis parameter falls below normal. Thus, improving sperm parameters can be an imperfect proxy for investigating how one behavior change impacts a man’s ability to conceive. That said, it’s often the best proxy we have.
Smoking has a negative impact on sperm concentration and morphology. One illustration, shown below, is a retrospective study on the semen parameters of 614 Singaporean men. The data shows men who smoke have statistically lower levels of sperm concentration and morphology. While the study is imperfect (no “live birth rate” endpoint), it does a nice job of tracking men who have few other issues (excessive drinking, a partner who smokes) making it easier to isolate the possible impact of smoking.
And when the investigators sub-segmented out the pool of smokers by their smoking frequency (cigarette years = cigarettes per day x number of years smoking), a similar trend was noted. This implies that best we can tell, any level of smoking hurts a man’s results on the semen analysis.
And in case you think, “well, we can still get pregnant with poor semen parameters by using IVF and ICSI,” in the case of smoking, you’d be wrong. A German team looked just at this issue in 2003 and showed that amongst over 700 couples, IVF cycles, both with and without ICSI, had far lower pregnancy rates when the man smoked (again, they didn’t study live birth rates, which is a shortcoming). You can see the findings below. After correcting for a few variables, the authors determined that a man’s smoking was a major impediment to IVF’s success, even if ICSI was used in the process.
A large, well-designed study of couples in Michigan and Texas looked at how lifestyle choices impact rates of miscarriage. As you can see below, investigators determined that amongst couples who conceive there is a 73% higher rate of miscarriage if the man drinks at least two or more caffeinated beverages per day.
In the context of a couple doing IVF, male consumption of caffeine probably begins to have an impact after around 200 milligrams per day, or about 1.5 – 2.0 caffeinated drinks per day. Below is the work from the team at Massachusetts General Hospital, who observed only a small number of patients, but did a nice job isolating variables (like smoking and alcohol consumption) and looked at the real world endpoint of live birth rate.
We have less conviction on the role alcohol plays in a man’s ability to conceive. Similar to smoking, most of our studies only measure how alcohol consumption impacts semen parameters, not live birth rates. Furthermore, there is a larger number of studies on this subject that make differing observations and come to differing conclusions.
The best study in the field, we believe, measures semen parameters amongst a large number (1,200+) of 18 – 20 year old Danish men. As you can see below, the investigators saw a plausible impact on sperm concentration at 6 – 10 drinks per week, and then a more consistent impact above 25 drinks per week. Indeed, most reproductive urologists believe alcohol inhibits male fertility, but has a “threshold effect” in that only above certain levels does drinking alcohol become problematic.
A natural follow-on question is, how does male alcohol consumption impact the results for a couple who is beginning IVF? With the data we have available today, it’s unclear. The same team at Massachusetts General Hospital that studied caffeine’s effects looked at this issue. The MGH team noted that men in the highest drinking quartile (1.4 drinks per day) had higher live birth rates than the men in the lowest quartile. All the same, the sample set was small, the men in the top quartile still drank in relative moderation (again, 1.4 drinks per day) and we do not believe men should read into this data that increased alcohol consumption is helpful.
A male’s weight likely correlates with his ability to conceive naturally. When a Norwegian team analyzed 20,000 patients of retrospective data, and isolated out confounders (mainly their female companion’s body mass index), men with a higher body mass index were nearly 50% less likely to conceive naturally after 12 months. Typically, men who are of higher weight overproduce estrogen and struggle to produce testosterone, likely impacting their ability to produce sperm.
What’s also interesting here is that men with a lower body mass index (e.g. less than 20) were possibly the least likely to conceive quickly.
While this trial has flaws (e.g. patients self-reported height and weight), we like the sample size, statistical approach and fact that the endpoint of pregnancy is closer to live birth rate than simple changes in semen parameters.
When we look at how male weight, or body mass index, impacts a couple’s success rate during IVF, the answers are inconclusive. One large meta-analysis (a study of studies, which has its own issues) concluded overweight men who participate in IVF have lower success rates than men of normal weight. But again, the overall body of data is conflicting and hard to interpret.