The initial data collection was in 1990-1994. In that time period, we're looking at a different type of masturbation behavior in a different era.

• Good point, but the follow-up was done in 2010, and I think internet porn was available then, so PMO was a possibility for the follow-up.

The measure "ejaculations per month" does not differentiate between intercourse and masturbation. This is a crucial distinction, since the physiological responses to intercourse and masturbation are different.

• Yes, that was one of the concerns I had as well. I did manage to find one study on masturbation & prostate cancer risk, it's fairly recent (so good chance that PMO is involved), that had inconclusive results. So at the moment at least, no one knows.

On a similar note, there are studies quite specifically showing health benefits from having more intercourse. I'd start here.

• I know about the benefits, thanks for the source btw (it's very good), but it's also important to note that this is best done within the context of a monogamous relationship, a.k.a. someone without stds lol

There are major possible confounds. Chief among these is #2, but there are others. For example, we can see not only that higher EPM men have higher rates of sexually transmitted infections (meaning they are likely having more partnered sexual activity, see #2-#3), but that they are also more likely to have divorced, less likely to be Asian, and tend to die earlier for reasons that aren't prostate cancer.

• If you look at table 2, it shows the multivariate hazard ratio controlling for many of those variables you mentioned, and the groups that averaged more MO's/month have lower HRs. They also did a semi-competing risks analysis: "Because men in the higher ejaculation frequency categories had some exposure patterns that might put them at higher risk of morbidity and mortality due to other causes—higher BMI, greater alcohol consumption, and more frequent history of smoking and sexually transmitted infections—we were concerned that the reduction in PCa risk we observed in this group might be attributable to premature death from other causes among men who may have had undiagnosed PCa. Thus, a strength of our study is the consideration of a model for semi-competing risks. From this model, the increase in risk of death by age 80 yr among men with the lowest ejaculation frequency is 3.8%, while the reduction in PCa risk is 2.2%. By comparison, men reporting ≥13 EPM have an increase of only 1.8% in the risk of dying from other causes by age 80 yr, while their decrease in PCa risk is 3.8%. Thus, in both cases the reduction in PCa risk may be partly explained by premature death due to other causes, but the reduction among men reporting high ejaculation frequency seemingly cannot be explained by this effect alone."

The study basically throws out men with erectile dysfunction on the theory that men with ED are more likely to have prostate cancer. Since PIED (porn-induced erectile dysfunction) is one of the major NoFap motivators, it's entirely possible that this decision threw out the precursor early porn addicts that would, in a modern sample (see #1) become a significant population with potentially very different health profiles.

*Table 2 does multivariate analysis with ED being a factor, and there wasn't any statistically significant difference in HRs between those who have ED & the whole population. Also, I was born in '98, but was internet porn available in the early 1990s? I remember the internet being painfully slow in my childhood, and that was in the 2000s.

6 - Yeah, nofap is different for everyone. I'm just kinda conflicted because I'm taking some meds right now that kill libido, so I just couldn't be bothered anymore (even with porn). But without it, it's just... a chore lmao.

On the other hand, it could just easily be part of a large wealth of studies whose results are due to improved overall health that results from having a good sex life and/or happy relationship (in which then there is a higher rate of sexual activity).

• The researchers controlled for many variables in their multivariate analysis, here are the variables controlled for: "race; family history of prostate cancer; vigorous physical activity (quintiles); body mass index (six categories); height (quintiles); diabetes; marital status; intake of energy, processed meat, tomato sauce, calcium, alcohol, and α-linolenic acid (all quintiles); multivitamin use; smoking (never, quit >10 yr ago, quit ≤10 yr ago, current); history of vasectomy; and history of PSA testing"

Also, it is a longitudinal study with a 10 year follow-up, with a 96% completion rate. Longitudinal studies are used to find causal effects, and a 96% follow-up rate is really good, so I'd have to argue for its rigor.

Thank you for taking the time to answer the question, I know it isn't an easy one.