I won't dwell on his barely-disguised intent too much, because Yawning Bread readers are intelligent enough to see through it all.

This doesn't mean that I am denying that the HIV prevalence rate among men who have sex with men (MSM) is probably significantly higher than among men who have sex with women (MSW). What I take issue with is his attempt to extend this into moral admonitions against the bogeyman, the "high-risk gay lifestyle".

Consider this: diabetes is more prevalent among Malays than among Chinese, and indeed it is related to the diet and exercise levels of many Malays. But do we go around moralising and warning about the "high-risk Malay lifestyle" with the subtext that they should change into Chinese? Or to use this line of argument to justify making it criminal to be Malay.

Instead, what I wish to focus on in this essay is Alan Chin's use of numbers. It's the trick he uses to give himself the gloss of authority and scientificity, but when you look closely, they are highly suspect.

Before I come to his numbers, however, I need to deal with Balaji Sadasivan's.

* * * * *

 
A few weeks ago, the Straits Times carried this report:

17 July 2007
Straits Times

Many more Singaporeans are HIV positive and don't know it

The number of people with HIV here is much higher than thought, going by a Health Ministry survey. It found that 1 in 350 patients in Singapore is HIV positive and don't know about it.

Dr Balaji Sadasivan revealed the findings of anonymous tests done on excess blood samples of 3,000 hospital patients earlier this year.

The Senior Minister of State for Information, Communications and the Arts, who was speaking at an Aids awareness event on Tuesday, added that the problem was more acute with male patients than female patients.

The male to female ratio of the undiagnosed HIV population in hospitals was 15 to 1.

Dr Balaji said the MOH survey was done anonymously, so the Government did not know what percentage of undiagnosed HIV cases existed in hospitals.

[truncated]

I noticed it immediately, but just wasn't exercised enough to write about it then. However, now that Alan Chin rests his case partially on Balaji's numbers, I cannot avoid dealing with them.

It's like this: Out of about 3,000 samples, 1 in 350 were found to be HIV-positive. That almost surely meant 8 or 9 samples. Yet Balaji said the male:female ratio was 15:1. How can 9 samples give you a 15:1 ratio? How many females were HIV-positive among the 8 or 9?

* * * * *

OK, now let's come to Alan Chin. Below is the letter that appeared today. At various points, I have inserted little red trapezoids, to mark the points which I will discuss further on.

8 August 2007
Straits Times Print Forum

Beware the high-risk 'gay lifestyle'

In the article, 'Most with Aids virus don't know they have it' (ST, July 18), Senior Minister of State Balaji Sadasivan announced that a study of 3,000 blood samples in government hospitals showed that 1 in 350 samples was positive for the human immunodeficiency virus (HIV) which causes Aids. The male to female ratio of these cases was 15:1.

What conclusions can we draw?

The 15:1 ratio means that the HIV epidemic is still confined mainly to the high-risk groups (concentrated epidemic) and has not spread to the general population (generalised epidemic). If it were already in the general population, the ratio would be much closer to 1:1.

Therefore we still have time to do something before the situation gets worse.

Who constitutes these high-risk groups?

Data released by the Ministry of Health on HIV last year showed two groups of men were responsible for approximately 83 per cent of HIV cases.

53 per cent of the cases were men who contracted HIV via unprotected high-risk heterosexual sex. This group was infected overseas or by local unlicensed prostitutes; our licensed prostitutes are screened for HIV.

30 per cent of the cases comprised men having sex with men (MSM). Based on the prevalence of 2.8 per cent of men being homosexual or bisexual, there are about 67,000 men in Singapore who engage in MSM.

I highlight this second high-risk group as it is a matter of public interest and concern, given the ongoing debate on the review of the Penal Code relating to Section 377A.

Extrapolating from the infection rate of 1 in 350 and 15:1 ratio of males to females, the conclusion is that among men who indulge in MSM, about one in 20 has HIV and does not know it.

This means that someone who indulges in MSM and has 20 sexual partners would have exposed himself to HIV.

A survey conducted in the United States has shown that 75 per cent of homosexual men have more than 100 sexual partners and 28 per cent of them have more than 1,000 partners.

I feel that not enough has been done to warn our youth that leading a 'gay lifestyle' is not cool. On the contrary, it is very unhealthy. There is a very high risk of contracting not only HIV but also a slew of other sexually transmitted diseases.

Dr Alan Chin Yew Liang

What is the basis for this figure of 2.8 per cent? It seems to be from the Laumann, Gagnon, Michael and Michaels (1994) study. According to a summary from the Kinsey Institute [1],

A research team at the University of Chicago headed a project that conducted interviews in 1992 of a random probability sample of 3,432 men and women in the U.S. between the ages of 18-59 (National Health and Social Life Survey). Homosexuality was viewed as a complex of same-gender behavior, desire, and identity. 9% of men and 4% of women reported having engaged in at least one same-gender sexual activity since puberty. Given the identity category choices of heterosexual, homosexual, bisexual, or something else, 2.8% of men and 1.4% of women surveyed reported "some level of homosexual identity."

(emphasis added by Yawning Bread)

Alan Chin has conveniently taken the figure for homosexual identity and used it when discussing sexual behaviour. I cannot believe that he is unaware that many men who think of themselves as heterosexual also engage in sex with other men [2]. Identity is not the same as behaviour. Study after study has shown that.

In this regard, the Kinsey Institute, summarising another study (Binson, Michaels, Stall Coates, Gagnon and Catania, 1995) noted that,

Data on the prevalence of homosexual behavior and the demographic distribution of homosexual and bisexual men were analyzed from two national probability surveys (General Social Survey - GSS and the National Health and Social Life Survey - NHSLS) and a probability survey of urban centers in the U.S. (National AIDS Behavioral Surveys - NABS) and results from earlier surveys discussed. Combined data from the GSS and NHSLS surveys showed 5.3% of men reporting sexual activity with a same-gender partner since age 18. Data from the NABS showed 6.5% of men reporting sex with men during the previous five years. The highest prevalence was found in central cities of the 12 largest SMSAs (14.4% since age 18) and among "highly educated" White males (10.8%).

As you can see, measuring the prevalence of homosexuality is a tricky exercise with widely differing results. When I saw Alan Chin using a single figure, it struck me as suspicious. This is especially as the rest of his computations depended on that figure, which he never bothered to explain or qualify.

The next figure he used was "67,000 men in Singapore who engage in MSM." Where did that figure come from? He didn't say.

I would rather start from data from the Department of Statistics. The latest population data (citizens and permanent residents) they have is for June 2006. [3] 

Total population: 3.608 million 

Males aged 15 and above: 1.429 million 

Depending on the percentage figure assumed, the numbers of MSM among Singapore citizens and permanent residents vary a great deal. I can't figure out where he got "67,000" from. More to the point, it is misleading to imagine certainty in numbers when there clearly is not.

Using his debatable assumptions, Alan Chin asserted that 1:20 MSM are HIV-positive. How reliable is that estimate? If I go through the numbers from the start again, this is what I get:

According to Balaji, 1 in 350 are HIV-positive, thus there would be about 10,300 HIV-positive people out of a total population of 3.608 million. However, we should bear in mind that Balaji was referring to 1 in 350 hospital patients, not 1 in 350 people at large, a caveat which we will ignore for now, though it may actually be important.

What about the split between MSM and MSW for these 10,300 undiagnosed cases?

For 2006, the Ministry of Health reports [4] that of the 357 cases reported that year, 330 (92%) were infected through sex. Of these, 222 (67.3% of 330) were heterosexually active, 94 (28.5%) were homosexual, and 14 (4.2%) bisexual.

(Since there are no known cases of lesbians being HIV-positive, I can assume that all the homosexually-transmitted cases refer to men)

Let's assume that undiscovered infections follow the same pattern -- though it may not be true, since I understand that gay men are more likely to go for testing than straight men. In that case, about 28.5 percent of the undiscovered reservoir of 10,300 HIV-positives would be MSM, i.e. 2,936 persons.

As you can see, depending on one's assumptions, the ratio obtained can vary vastly, from 1:14 to 1:70

Alan Chin's exclusive use of the "1 in 20" ratio is misleadingly precise.

Then Alan Chin goes off hyperventilating over the numbers of sexual partners some people can have. When it comes to risk however, the more important consideration is whether you're using protection or not, not how many people you show your dick to. You're better off having safe sex with 500 people than unsafe sex with 1.

This is where his moralising agenda becomes obvious. He has taken leave of sound medical advice (safe sex) to rant about the "gay lifestyle".

* * * * *

 
To close, I acknowledge that MSMs are a known risk group. It is not something to be whitewashed; if anything, it is something that deserves more attention, including such issues as how the criminalisation of homosexual sex obstructs public health efforts. But Alan Chin has added nothing useful to the mission. He's just confused everyone by his careless use of numbers to further his moralistic agenda, distracting us all. Every day that we don't do enough is a day that somebody dies.

© Yawning Bread