UPDATE: Read more about the “30 by 30” statistic at http://thirtybyagethirty.blogspot.com/
[Chairm has provided an excellent rebuttal to a recent, agitated commenter on this blog who just could not accept a statistic we quoted]
Among lots of other good stuff, Cura_te_ipsum cited the following:
“HIV/AIDS is rampant in the homosexual community. Epidemiologists estimate that 30 percent of all 20-year-old homosexually-active men will be HIV positive or dead of AIDS by the time they are 30.”
E. Goldman, “Psychological Factors Generate HIV Resurgence in Young Gay Men,” Clinical Psychiatry News, Oct. 1994.
And so J. Stone began his little sniping war against that statistical forecast. He repeated several times variations of the following:
“Do you really expect people to believe that 30% of sexually active gay 20 year olds contract HIV by the age of 30? That is the most preposterous statistic I’ve ever seen.”
For those readers who would like to know more about this forecast, here are the basics.
Statistical models are tools. Diagnosed infections are counted and sorted by relevant criteria. Incidence rates and prevalence ratios
are fed into the process whereby epidemiologists assess the available evidence and offer recommendations to help society respond to an
outbreak of disease. Forecasts form the basis for contingencies at multiple levels — from the individual person, to the local community,
to the nation and, in the HIV/AIDS pandemic, right through to the international level.
So it is normal that forecasts are made and estimates are made of current rates and ratios of infection. Note that J. Stone never,
throughout his sniping, proposed what statistic might pass his ‘sniff test‘. He offered no basis to assess any given forecast, much less
this particular 1995 forecast of HIV/AIDS.
Instead he said that 30% by age 30 is beyond credibility. He expressly doubted that the CDC had anything to do with such a
1. The CDC’s data is the basis for the 30% by 30 forecast. In 1994, epidemiologists at Columbia University reported that the CDC’s data
led them to forecast that
“lifetime individual risks of seroconversion of over 50 percent, with the highest annual hazard (4.4 percent per year) occurring before age 25 years.”
2. In 1995, clinical psychiatrist (and gay man in San Francisco), W. Odets, presented a paper to the international science community on the epidemiology of HIV/AIDS.
“Some simple epidemiology helps answer these questions: To date, more San Franciscans have died of AIDS – 90% of them gay men – than all the San Franciscans dead from the four wars of the 20th century, combined and quadrupled. Nationally, 30 percent of 20 year- old gay men will be infected with HIV or dead of AIDS by age 30. A majority of gay 20 year-olds will contract HIV during their lifetimes. In San Francisco, our current rates of seroconversion will much more than maintain a 50% prevalence of HIV infection indefinitely.”
Odets was not alone in making estimates in that range.
3. By 2001, researchers at the CDC reported that the HIV prevalence (i.e. those living with infection or with AIDS) in the 15-22 age group
“rose steadily with increasing age, to nearly 10% among 22-year-olds. […] The emerging data presented here suggest that we may be headed toward a resurgence in HIV infections among MSM”.
In other words, the prevalence and the incidence rate pointed toward fulfilling the 1995 forecast.
4. Since the outbreake of HIV/AIDS, the CDC has gathered statistics from across the country. By 2005, the CDC revised and refined its
analysis of the available evidence. It released more accurate incidence rates and prevalence rations.
The indications are that 30% by 30 had been fulfilled, tragically, in 1995-2005.
5. In 2005, a leading HIV/AIDS researcher at the CDC, R. Stall, presented his findings at the International AIDS Conference.
He reviewed the historical data and the current trends. Stall calculated the lifelong risk for twenty-year-old homosexually-active
men (i.e. men who have sex with men, aka MSM) of becoming infected with HIV. By age 30 — some ten years hence — about 25% would be
infected; 40% by age 40; and 50% by age 50.
6. In 2008, at the Conference on Retroviruses and Opportunistic Infections, R. Stall presented more research and a new forecast for
another ten years.
Taking as his starting point the current incidence of HIV infection among 15-22 year-old men who have sex with men (MSM), professor Stall ran a mathematic model to see how this would translate into HIV prevalence as the 18-year-old group got older.
In a press conference he explained:
“The model that we constructed yielded an estimate that at about age 25, about 15% of the men would be HIV positive; by age 35, about a third; and by age 40, about 41%.”
“We were kind of horrified that our model yielded prevalence estimates that high. […] What we find is that the model actually fits exactly what’s going on in terms of HIV prevalence among gay men, at least in America’s largest urban centers. This model that we are extrapolating based on the incidence rates, which culminates in an HIV prevalence rate of 40% at age 40, is not a prediction of something that may happen one day. We are describing epidemiological phenomena that are occurring all around us, and will continue to occur among young American men, if we do not find ways to lower HIV incidence rates
* * *
J. Stone ridiculed the 1995 forecast. He ridiculed as preposterous the high prevalance of HIV/AIDS among 30-year-olds. He derided the
estimate that by 30 almost 1 in 3 homosexually active men could be infected with HIV/AIDS or dead of AIDS.
“I want to reiterate that there is no way that 30% of sexually active gay 20 year olds contract HIV by the age of 30. How anyone could believe such an outrageous claim is beyond me.”
J. Stone waved away the heightened risk to homosexually-active young men. His rhetoric, actually, could be dangerous to the lives of people he claims to be defending.
J. Stone is wrong.