Yesterday, Australian Christian Lobby boss Jim Wallace told an audience debating gay marriage at the University of Tasmania that taking up smoking was a comparatively better lifestyle choice than engaging in the salacious activity associated with same-sex marriage.

“I think we’re going to owe smokers a big apology when the homosexual community’s own statistics for its health — which it presents when it wants more money for health — are that is has higher rates of drug-taking, of suicide, it has the life of a male reduced by up to 20 years,” he said. Smoking, by contrast, led to a reduced life expectancy of between seven and 10 years.

This morning, Prime Minister Julia Gillard pulled out of next month’s ACL conference in Canberra, condemning Wallace’s comments as “heartless and wrong”. How wrong? In another instalment of Crikey‘s Get Fact series, we put Wallace’s claims to the truth test.

There are a mountain of studies reporting poorer health outcomes among the gay community — gays are more likely to be smokers, to use and abuse drugs and to attempt suicide. In a follow-up ACL press release this morning, Wallace pointed to Canadian data sent to that country’s human rights commission showing troubling rates of alcohol use, depression, a lack of access to care, higher cancer risk and violence.

But what about life expectancy? Smokers may go to the grave a decade earlier but is a same-sex attracted person really likely to have their lives cut short simply because of their sexual preference?

Wallace’s claim about mortality — which he previously trotted out in The Australian last year — is repeatedly used by American anti-gay groups to ratchet up political support for the sanctity of marriage. But the foundation for the statement is dubious and contested.

Much of the “data” supporting that claim relates to gay men in an urban HIV subset (as opposed to say, lesbians in a civil union), and is at least 20 years old.

Wallace’s life expectancy claims could stem from a 1997 study in the International Journal of Epidemiology which concluded that “in a major Canadian centre (Vancouver), life expectancy at age 20 years for gay and bis-xual men is eight to 20 years less than for all men. If the same pattern of mortality were to continue, we estimate that nearly half of gay and bisexual men currently aged 20 years will not reach their 65th birthday.

“Under even the most liberal assumptions, gay and bisexual men in this urban centre are now experiencing a life expectancy similar to that experienced by all men in Canada in the year 1871,” the study said.

But the data in that study was collected between 1987 and 1992, well before advanced treatments for HIV were developed. In 2001, its authors published a follow-up study blasting “select groups in US and Finland” for exploiting the research to “suggest that gay and bis-xual men live an unhealthy lifestyle that is destructive to themselves and to others”. They wrote:

“If we were to repeat this analysis today the life expectancy of gay and bis-xual men would be greatly improved. Deaths from HIV infection have declined dramatically in this population since 1996 …

“It is essential to note that the life expectancy of any population is a descriptive and not a prescriptive measure. Death is a product of the way a person lives and what physical and environmental hazards he or she faces every day. It cannot be attributed solely to their s-xual orientation or any other ethnic or social factor.”

A 2009 Danish study published in the American Journal of Public Health found that while death rates among same-sex married couples was a third higher than the general population from1989 to 2004, after 1996 the mortality rate among gay men in same-sex marriages was similar to heterosexuals.

Another source favoured by gay marriage opponents is Cameron, Playfair and Wellum’s widely debunked “gay obituary” study published in 1994 in the Omega Journal of Death and Dying. It concluded gay men have an average lifespan of 43 years. The study involved researchers consulting the death notices — mostly AIDS-related — in the urban gay community press.

The problem was the study suffered from what statisticians call a “non response bias” — that is, the sample was corrupted by the non-inclusion of gay men who were still alive. According to statisticians from Columbia University, the average age of AIDS victims is about 40. But even before new treatments became widely available, only about 20% of gay men were likely to die of AIDS.

Cameron, the founder of recognised hate group Family Research Institute, followed that up with this pseudo 1998 study, “Does Homosexual Activity Shorten Life“. That was again based on surveys of gay obituaries and other “random surveys” and found the “medium age of death” for homosexuals was less than 50 years. The evidence was “consistent with previous findings suggesting that homosexual activity may be associated with a lifespan shortened by 20 to 30 years”.

Even excusing its dodgy methodology, treatment advances have rendered the conclusions defunct. As Andrew Carr, director of the HIV, immunology and infectious diseases unit at St Vincent’s Hospital, told The Sydney Morning Herald in July: ”Once upon a time the average person who got HIV had a life expectancy of about 10 years. Now, if you get HIV and go on treatment your life is still probably shorter than if you had never had the virus, but maybe only five to 10 years less.”

Carr said that when groups prone to HIV are stripped out, notably injecting drug users, then the difference becomes even smaller. And in the US, the death rate from HIV was nine times higher in 1990 than two years ago.

One of the other studies cited by Wallace in the past — a 2003 Dutch study — found on average gay relationships only last 18 months. Those findings, published in the journal AIDS, were based on a cohort of young Dutch gays aged 18-21 residing in the middle of Amsterdam.

In fact, other research, including a study in the US state of Vermont — the first state to legalise same-sex civil unions — showed civil union households seemed to mirror that of the general population. Crucially, the data did not require “participants” or volunteers that skewed the result — it was a simple reading of the information collected by state bureaucrats.

Peversely, it is likely that media interventions like Wallace’s may in fact perpetuate many the health problems he is himself referring to. A recent study from the University of Queensland, The Psychology of Same-Sex Marriage Opposition, showed that individuals exposed to media articles bagging same-sex marriage were more likely to report feeling negative and depresseda nd more likely to feel distressed, upset, guilty, scared, afraid, ashamed and nervous. They were more likely to report loneliness, more likely to report they felt weak and powerless — and less likely to report feeling happy or positive.

A recent Psychologists for Marriage Equality submission to the Senate inquiry into the gay marriage bill cited a 2007 study showing the phenomenon of “minority stress” means “social prejudice, discrimination, and violence against lesbians, gay men, and bisexuals play a significant role in the mental health outcomes” of these groups.

So, while the gay population does appear to experience a disproportionate prevalence of negative health effects brought on by others, the evidence that gays die earlier than straights is tenuous at best. Accordingly, we rate Wallace’s claims mostly rubbish.