Wednesday, August 06, 2008

Religion and health

Does religious diversity go with poorer health? It says below that it does. But surely the USA has huge religious diversity and also high health standards? But I guess that most American denominations could all be lumped together as "Protestant" or some such. A Baptist, for instance, would not normally feel uncomfortable in a Methodist church (though he might feel uncomfortable in some other Baptist churches!)

Some people, notably Richard Dawkins, an evolutionary biologist at Oxford University, regard religion as a disease. It spreads, they suggest, like a virus, except that the "viruses" are similar to those infecting computers-bits of cultural software that take over the hardware of the brain and make it do irrational things.

Corey Fincher, of the University of New Mexico, has a different hypothesis for the origin of religious diversity. He thinks not that religions are like disease but that they are responses to disease-or, rather, to the threat of disease. If he is right, then people who believe that their religion protects them from harm may be correct, although the protection is of a different sort from the supernatural one they perceive.

Mr Fincher is not arguing that disease-protection is religion's main function. Biologists have different hypotheses for that. Not all follow Dr Dawkins in thinking it pathological. Some see it either as a way of promoting group solidarity in a hostile world, or as an accidental consequence of the predisposition to such solidarity. This solidarity-promotion is one of Mr Fincher's starting points. The other is that bacteria, viruses and other parasites are powerful drivers of evolution. Many biologists think that sex, for example, is a response to parasitism. The continual mixing of genes that it promotes means that at least some offspring of any pair of parents are likely to be immune to a given disease.

Mr Fincher and his colleague Randy Thornhill wondered if disease might be driving important aspects of human social behaviour, too. Their hypothesis is that in places where disease is rampant, it behoves groups not to mix with one another more than is strictly necessary, in order to reduce the risk of contagion. They therefore predict that patterns of behaviour which promote group exclusivity will be stronger in disease-ridden areas. Since religious differences are certainly in that category, they specifically predict that the number of different religions in a place will vary with the disease load. Which is, as they report in the Proceedings of the Royal Society, the case.

Proving the point involved collating a lot of previous research. Even defining what constitutes a religion is fraught with difficulty. But using accepted definitions of uniqueness, exclusivity, autonomy and superiority to other religions they calculated that the average number of religions per country is 31. The range, though, is enormous-from 3 to 643. C"te d'Ivoire, for example, has 76 while Norway has 13, and Brazil has 159 while Canada has 15. They then did the same thing for the number of parasitic diseases found in each country. The average here was 200, with a range from 178 to 248.

Obviously, some of the differences between countries are caused by differences in their areas and populations. But these can be accounted for statistically. When they have been, the correlation between the number of religions in a place and how disease-ridden it is looks impressive. There is less than one chance in 10,000 that it has come about accidentally.

The two researchers also looked at anthropological data on how much people in "traditional" (ie, non-urban) societies move around in different parts of the world. They found that in more religiously diverse (and more disease-ridden) places people move shorter distances than in healthier, religiously monotonous societies. The implication is that religious diversity causes people to keep themselves to themselves, and thus makes it harder for them to catch germs from infidels.

Of course, correlation is not causation. But religion is not the only cultural phenomenon that stops groups of people from mixing. Language has the same effect, and in another, as yet unpublished study Mr Fincher and Dr Thornhill found a similar relationship there too. Moreover, their search of the literature turned up work which suggests that xenophobia is linked psychologically with fear of disease (the dirty foreigner.). Perhaps, then, the underlying reason why there is so much hostility between ethnic groups is nothing to do with the groups themselves, but instead with the diseases they may bring.


Antibiotic HINDERS treatment of AIDS

A drug used to fight tuberculosis also hampers the effectiveness of an HIV treatment widely used in Africa, the world's worst AIDS-hit region, a study published today says. The antibiotic rifampicin reduces concentrations in the blood of nevirapine, a low-cost agent that is part of the frontline therapy against HIV in poor countries, especially Africa.

The study was presented ahead of the start of the 17th International AIDS Conference, which runs in Mexico City until Friday. The evidence comes from a study, unfolding in South Africa between 2001 and 2006, among 2,035 individuals who began their treatment with efavirenz, 1,074 of whom had TB, and 1,935 others who initiated with nevaripine, of whom 209 also had TB. In the nevaripine group, 16.3 per cent patients with TB were nearly twice as likely to have elevated levels of HIV in their blood at a six-month follow-up check compared to 8.3 per cent among those without TB. They were also twice as likely to develop treatment failure faster than patients who did not have TB. However, a large majority - 80 per cent - of TB patients using nevirapine also succeeded in suppressing the virus at an 18-month check-up.

The findings are of high importance for sub-Saharan Africa, which is home to two-thirds of the 33 million people infected by the human immunodeficiency virus (HIV). Around the world, an estimated one-third of the persons living with HIV are co-infected with TB. For reasons that are poorly understood, co-infection can cause a lightning-fast decline in health, especially if the TB strain is resistant to frontline antibiotics. The death rate among cases of co-infection is five times higher than for tuberculosis alone.

The JAMA study, led by Andrew Boulle of the University of Cape Town, South Africa, said it was unclear why rifampicin had such an impact on nevaripine. One possible reason could be a shared toxicity. Another could be a drug interaction, caused by rifampicin, when the patient started to receive early doses of the antiretroviral. Anti-HIV drugs suppress the virus but do not eradicate it completely. If the drugs are halted, the AIDS rebounds.

The study appears in next Wednesday's issue of the Journal of the American Medical Association (JAMA).


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