Quantified Risks of Gay Male Sex
If you are a gay male then you’ve probably worried at one point about sexually transmitted diseases. Indeed men who have sex with men have some of the highest prevalence of many of these diseases. And if you’re not a gay male, you’ve probably still thought about STDs at one point. But how much should you worry? There are many organizations and resources that will tell you to wear a condom, but very few will tell you the relative risks of wearing a condom vs not. I’d like to provide a concise summary of the risks associated with gay male sex and the extent to which these risks can be reduced. (See Mark Manson’s guide for a similar resources for heterosexual sex.). I will do so by first giving some information about each disease, including its prevalence among gay men. Most of this data will come from the US, but the US actually has an unusually high prevalence for many diseases. Certainly HIV is much less common in many parts of Europe. I will end with a case study of HIV, which will include an analysis of the probabilities of transmission broken down by the nature of sex act and a discussion of risk reduction techniques.
When dealing with risks associated with sex, there are few relevant parameters. The most common is the prevalence – the proportion of people in the population that have the disease. Since you can only get a disease from someone who has it, the prevalence is arguably the most important statistic. There are two more relevant statistics – the per act infectivity (the chance of contracting the disease after having sex once) and the per partner infectivity (the chance of contracting the disease after having sex with one partner for the duration of the relationship). As it turns out the latter two probabilities are very difficult to calculate. I only obtained those values for for HIV. It is especially difficult to determine per act risks for specific types of sex acts since many MSM engage in a variety of acts with multiple partners. Nevertheless estimates do exist and will explored in detail in the HIV case study section.
HIV
Prevalence: Between 13 - 28%. My guess is about 13%.
The most infamous of the STDs. There is no cure but it can be managed with anti-retroviral therapy. A commonly reported statistic is that 19% of MSM (men who have sex with men) in the US are HIV positive (1). For black MSM, this number was 28% and for white MSM this number was 16%. This is likely an overestimate, however, since the sample used was gay men who frequent bars and clubs. My estimate of 13% comes from CDC's total HIV prevalence in gay men of 590,000 (2) and their data suggesting that MSM comprise 2.9% of men in the US (3).
Gonorrhea
Prevalence: Between 9% and 15% in the US
This disease affects the throat and the genitals but it is treatable with antibiotics. The CDC estimates 15.5% prevalence (4). However, this is likely an overestimate since the sample used was gay men in health clinics. Another sample (in San Francisco health clinics) had a pharyngeal gonorrhea prevalence of 9% (5).
Syphilis
Prevalence: 0.825% in the US
My estimate was calculated in the same manner as my estimate for HIV. I used the CDC's data (6). Syphilis is transmittable by oral and anal sex (7) and causes genital sores that may look harmless at first (8). Syphilis is curable with penicillin however the presence of sores increases the infectivity of HIV.
Herpes (HSV-1 and HSV-2)
Prevalence: HSV-2 - 18.4% (9); HSV-1 - ~75% based on Australian data (10)
This disease is mostly asymptomatic and can be transmitted through oral or anal sex. Sometimes sores will appear and they will usually go away with time. For the same reason as syphilis, herpes can increase the chance of transmitting HIV. The estimate for HSV-1 is probably too high. Snowball sampling was used and most of the men recruited were heavily involved in organizations for gay men and were sexually active in the past 6 months. Also half of them reported unprotected anal sex in the past six months. The HSV-2 sample came from a random sample of US households (11).
Clamydia
Prevalence: Rectal - 0.5% - 2.3% ; Pharyngeal - 3.0 - 10.5% (12)
Like herpes, it is often asymptomatic - perhaps as low as 10% of infected men report symptoms. It is curable with antibiotics.
HPV
Prevalence: 47.2% (13)
This disease is incurable (though a vaccine exists for men and women) but usually asymptomatic. It is capable of causing cancers of the penis, throat and anus. Oddly there are no common tests for HPV in part because there are many strains (over 100) most of which are relatively harmless. Sometimes it goes away on its own (14). The prevalence rate was oddly difficult to find, the number I cited came from a sample of men from Brazil, Mexico and the US.
Case Study of HIV transmission; risks and strategies for reducing risk
IMPORTANT: None of the following figures should be generalized to other diseases. Many of these numbers are not even the same order of magnitude as the numbers for other diseases. For example, HIV is especially difficult to transmit via oral sex, but Herpes can very easily be transmitted.
Unprotected Oral Sex per-act risk (with a positive partner or partner of unknown serostatus):
Non-zero but very small. Best guess .03% without condom (15)
Unprotected Anal sex per-act risk (with positive partner):
Receptive: 0.82% - 1.4% (16) (17)
Insertive Circumcised: 0.11% (18)
Insertive Uncircumcised: 0.62% (18)
Protected Anal sex per-act risk (with positive partner):
Estimates range from 2 times lower to twenty times lower (16) (19) and the risk is highly dependent on the slippage and breakage rate.
Contracting HIV from oral sex is very rare. In one study, 67 men reported performing oral sex on at least one HIV positive partner and none were infected (20). However, transmission is possible (15). Because instances of oral transmission of HIV are so rare, the risk is hard to calculate so should be taken with a grain of salt. The number cited was obtained from a group of individuals that were either HIV positive or high risk for HIV. The per act-risk with a positive partner is therefore probably somewhat higher.
Note that different HIV positive men have different levels of infectivity hence the wide range of values for per-act probability of transmission. Some men with high viral loads (the amount of HIV in the blood) may have an infectivity of greater than 10% per unprotected anal sex act (17).
Risk reducing strategies
Choosing sex acts that have a lower transmission rate (oral sex, protected insertive anal sex, non-insertive) is one way to reduce risk. Monogamy, testing, antiretroviral therapy, PEP and PrEP are five other ways.
Testing Your partner/ Monogamy
If your partner tests negative then they are very unlikely to have HIV. There is a 0.047% chance of being HIV positive if they tested negative using a blood test and a 0.29% chance of being HIV positive if they tested negative using an oral test. If they did further tests then the chance is even lower. (See the section after the next paragraph for how these numbers were calculated).
So if your partner tests negative, the real danger is not the test giving an incorrect result. The danger is that your partner was exposed to HIV before the test, but his body had not started to make antibodies yet. Since this can take weeks or months, it is possible for your partner who tested negative to still have HIV even if you are both completely monogamous.
____
For tests, the sensitivity - the probability that an HIV positive person will test positive - is 99.68% for blood tests (21), 98.03% with oral tests. The specificity - the probability that an HIV negative person will test negative - is 99.74% for oral tests and 99.91% for blood tests. Hence the probability that a person who tested negative will actually be positive is:
P(Positive | tested negative) = P(Positive)*(1-sensitivity)/(P(Negative)*specificity + P(Positive)*(1-sensitivity)) = 0.047% for blood test, 0.29% for oral test
Where P(Positive) = Prevalence of HIV, I estimated this to be 13%.
However, according to a writer for About.com (22) - a doctor who works with HIV - there are often multiple tests which drive the sensitivity up to 99.997%.
Home Testing
Oraquick is an HIV test that you can purchase online and do yourself at home. It costs $39.99 for one kit. The sensitivity is 93.64%, the specificity is 99.87% (23). The probability that someone who tested negative will actually be HIV positive is 0.94%. - assuming a 13% prevalence for HIV. The same danger mentioned above applies - if the infection occurred recently the test would not detect it.
Anti-Retroviral therapy
Highly active anti-retroviral therapy (HAART), when successful, can reduce the viral load – the amount of HIV in the blood - to low or undetectable levels. Baggaley et. al (17) reports that in heterosexual couples, there have been some models relating viral load to infectivity. She applies these models to MSM and reports that the per-act risk for unprotected anal sex with a positive partner should be 0.061%. However, she notes that different models produce very different results thus this number should be taken with a grain of salt.
Post-Exposure Prophylaxis (PEP)
A last resort if you think you were exposed to HIV is to undergo post-exposure prophylaxis within 72 hours. Antiretroviral drugs are taken for about a month in the hopes of preventing the HIV from infecting any cells. In one case controlled study some health care workers who were exposed to HIV were given PEP and some were not, (this was not under the control of the experimenters). Workers that contracted HIV were less likely to have been given PEP with an odds ratio of 0.19 (24). I don’t know whether PEP is equally effective at mitigating risk from other sources of exposure.
Pre-Exposure Prophylaxis (PrEP)
This is a relatively new risk reduction strategy. Instead of taking anti-retroviral drugs after exposure, you take anti-retroviral drugs every day in order to prevent HIV infection. I could not find a per-act risk, but in a randomized controlled trial, MSM who took PrEP were less likely to become infected with HIV than men who did not (relative reduction - 41%). The average number of sex partners was 18. For men who were more consistent and had a 90% adherence rate, the relative reduction was better - 73%. (25) (26).
1: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5937a2.htm?s_cid=mm5937a2_w
2: http://www.cdc.gov/hiv/statistics/basics/ataglance.html
3: http://www.cdc.gov/nchs/data/ad/ad362.pdf
4: http://www.cdc.gov/std/stats10/msm.htm
5: http://cid.oxfordjournals.org/content/41/1/67.short
6: http://www.cdc.gov/std/syphilis/STDFact-MSM-Syphilis.htm
7: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5341a2.htm
8: http://www.cdc.gov/std/syphilis/stdfact-syphilis.htm
10: http://jid.oxfordjournals.org/content/194/5/561.full
11: http://www.nber.org/nhanes/nhanes-III/docs/nchs/manuals/planop.pdf
12: http://www.cdc.gov/std/chlamydia/STDFact-Chlamydia-detailed.htm
13: http://jid.oxfordjournals.org/content/203/1/49.short
14: http://www.cdc.gov/std/hpv/stdfact-hpv-and-men.htm
16: http://aje.oxfordjournals.org/content/150/3/306.short
17: http://ije.oxfordjournals.org/content/early/2010/04/20/ije.dyq057.full
18: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2852627/
19:
20:
21: http://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2811%2970368-1/abstract
22:
23: http://www.ncbi.nlm.nih.gov/pubmed/18824617
24: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002835.pub3/abstract
25: http://www.nejm.org/doi/full/10.1056/Nejmoa1011205#t=articleResults
Community bias in threat evaluation
If I were to ask the question "What threat poses the greatest risk to society/humanity?" to several communities I would expect to get some answers that follow a predictable trend:
If I asked the question on an HBD blog I'd probably get one of the answers demographic disaster/dysgenics/immigration.
If I asked the question to a bunch of environmentalists they'd probably say global warming or pollution.
If I asked the question on a leftist blog I might get the answer: growing inequality/exploitation of workers.
If I asked the question to Catholic bishops they might say abortion/sexual immorality.
And if I were to ask the question on LessWrong (which is heavily populated by Computer scientists and programmers) many would respond with unfriendly AI.
One of these groups might be right, I don't know. However I would treat all of their claims with caution.
Edit: This may not be a bad from thing from an instrumental rationality perspective. If you think that the problem you're working on is really important then you're more likely to put a good effort into solving it.
Some thoughts on having children
Disclaimer: I am not a parent.
I've seen a bit of discussion here on whether or not to have children. Most of the discussion that I have seen are about the moral case, but there are factors as well. I'd like to talk about three aspects of parenting that I suspect are the main reasons why people choose to have kids or not: the financial case, the moral case, and the practical case (for lack of a better term). The financial case is straightforward - how expensive is raising kids? The moral case has to do with the best use of resources: is it better to divert resources away from having kids towards charity? The practical case has to do with the actual process of being a parent - the effort it takes and the sense of responsibility.
The Practical Case
I suspect that the main reason for why people don't have kids is because they think that kids are a lot of responsibility because:
1) It takes a lot of work and effort to raise children - effort that could be spent on other activities.
2) Great parenting is extremely important for raising well adjusted, intelligent kids that will grow up to be successful and likable adults.
Regarding 1) yes kids do take a lot of time and effort, but that's not necessarily a bad thing - lots of things that are rewarding require a lot of effort, such as learning a language or a new skill. I don't know what its like to a parent so I won't say much more on this topic.
Regarding 2) it is actually far from a settled question whether parenting style significantly affects the kind of person that your child will grow up to be. There has been some discussion here on the effects of parenting on children. The tentative consensus seems to be that within the range of normal parenting, parenting style has only small impact life outcomes pertaining to happiness, personality, educational achievement. That doesn't mean that how you treat your child doesn't matter. Steven Pinker puts it quite nicely:
Judith Rich Harris is coming out with a book called The Nurture Assumption which argues that parents don’t influence the long-term fates of their children; peers do. The reaction she often gets is, “So are you saying it doesn’t matter how I treat my child?” She points out that this is like someone learning that you can’t change the personality of your spouse and asking, “So are you saying that it doesn’t matter how you treat my spouse?” People seem to think that the only reason to be nice to children is that it will mold their character as adults in the future — as opposed to the common-sense idea that you should be nice to people because it makes life better for them in the present. Child rearing has become a technological matter of which practices grow the best children, as opposed to a human relationship in which the happiness of the child (during childhood) is determined by how the child is treated. She has a wonderful quote: “We may not control our children’s tomorrows, but we surely control their todays, and we have the capacity to make them very, very miserable.”
The message I would take away is not to worry too much about creating an optimal child. Don't worry about finding the optimal set of extra-curricular activities or the perfect balance of authoritarianism and permissiveness. Instead, try to cultivate a healthy relationship with your child and most of all enjoy the parenting process.
The Financial Case
In agarian societies (and most societies quite frankly) children were/are cheap, in some cases free labor and a life insurance policy for when you retire. But in the post-industrial Western world that is no longer the case. For a middle-upper class family, having a child is a very large cost for two reasons: the first is that children cost a lot of money to raise. The second reason is that having a child might hold you back from advancing your career as much as you would have been able to do otherwise. I will focus on the first problem here. According to the United States department of Agriculture, the average cost of raising a child to age 18 was about $241,080 (in 2012 dollars). This doesn't count the cost of college which can exceed $250,000 at elite institutions. I'll assume the $250,000 figure for the purposes of the following calculations.
Assuming that you are able to invest your money at a modest 5% rate of return, this amounts to having to put aside $8887 each year from your child's birth for college only, and approximately $13,000 (2012 dollars) per year on other expenses such as housing and food. That $13,000 per year figure does not account for inflation and in reality that figure would grow each year but this is just to provide a rough ball-park figure. This figure goes up if you have more than one child but the per child cost goes down.
This brings up the issue of whether or not you "owe" your child an all expenses paid college education. I wouldn't rule out only paying partially for your child's college education especially since this calculation assumes only one child. I would be interested to hear more thoughts on this matter.
The Moral Case
Some effective altruists have advanced the idea that having children is immoral because the money spent on having kids would be better spent by donating it to charity. This assumes utilitarianism, and indeed if GiveWell recommended charities were perfect or even pretty good util maximizers then this argument would succeed, since by design whatever they did would be the best use of money under utilitarianism. However, I do not believe that this is the case. GiveWell recommended charities that focus almost exclusively on public health initiatives, and exclusively focus on providing aid to the poorest countries. While a simple diminishing marginal returns argument might suggest that this is the lowest hanging fruit and hence the best use of money there are other things that need to be considered.
As Apprentice points out the heritability of prosocial behaviors such as cooperativeness, empathy and altruism is 0.5, and I think most people here are aware that IQ has a heritability around that number as well and is a pretty good predictor of life outcomes. If you want to increase the number of people in the world that are like yourself, then having children is a great way of doing so. This is particularly important since high IQ college educated individuals in Western countries have fertility rates that are below replacement levels and are some of the lowest in the world.
Rachels anticipates this argument by pointing out than one child is unlikely to produce the same returns as an investment in charity. I believe this is a mistake because it is short sighted. If you stop the utilitarian analysis at one generation into the future then yes having a smart altruistic child will not give the same returns as saving lives through charity, however consequentialism need not be short sighted. If you have more than one child, and/or if your children have children then the returns get magnified significantly - and it is worth noting that intelligent people contribute a lot to society not just through charity but through their work as well. Moreover, the people you would save by donating to charity would also have children and those children would have children all of whom might require yet more aid in the future. Thus the short term gains in QALYs that giving to GiveWell recommended charities provides lead to a long term drain of resources and human capital. And as I have already mentioned, intelligent people already have the lowest fertility in society, I'd rather not see it go even lower.
Jeff Kaufman provides two counterarguments that caught my eye: that this is an argument for sperm donation rather than having children; and that genetic engineering will solve the dysgenic fertility problem. However, sperm banks are already eugenic (in a sense) and it is fairly easy to saturate the supply of high quality sperm. Sperm donation is good idea for highly intelligent individuals (and to my surprise there are actually sperm donor shortages in some parts of the world making it an even better idea), but it is not a substitute for having children - the bottleneck quickly becomes the demand for said sperm. This is certainly a potential area worth investigating as a light form of eugenics, but I don't know of anyone who's trying to market eugenic sperm donation right now. With regard to genetic engineering, I have serious doubts that the field will develop to the point of commercialization in the next hundred years, and I have even stronger doubts that it will be widely accepted and used. While I realize that prediction of the future is very difficult, I would be very surprised if in a hundred years the average Joe will think about having genetically engineered children. Any mention of eugenics already invokes fear in the hearts of most people, and its pretty hard to deny that genetically engineering babies is the scariest kind of eugenics. Human genetic engineering might well solve the dysgenic problem, but I wouldn't bet strongly on that happening any time soon, whereas having children is an almost guaranteed way of helping to solve the problem.
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