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MINERVA: Minerva BMJ 2002; 324: 374 [Full text]

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Correlation not causation

Hugh P Young   (9 February 2002)

Not so fast, Minerva!

George Hill   (17 February 2002)

Correlation not causation 9 February 2002
Hugh P Young, none Pukerua Bay, New Zealand Send response to journal: Re: Correlation not causation	While it may be true that "Lack of male circumcision is significantly associated with HIV infection" (BMJ 2002;324:374, 9 February), it does not follow that circumcising babies, boys or men will protect anybody against HIV. Circumcision never happens in a social vacuum, and in Africa is confined to certain tribes and/or religions, all of which have correlations with sexual practice and hence HIV transmission. For example it is common that women from circumcising tribes will refuse sex with intact youths, delaying the onset of first intercourse in those tribes. The oft-quoted Rakei study, in which none of 50 circumcised men contracted HIV in up to 30 months, also found that another 29 of the circumcised men had HIV already and were excluded from the study. The suggestion that mass circumcision be implemented to prevent HIV transmission is being made commonly but prematurely. Some people seem to have a personal interest in promoting the practice. Æsop's fable about the fox's tale springs to mind. Promoting circumcision to protect against HIV would be dangerously counterproductive, with circumcised men (especially those who had recently undergone the painful procedure for this purpose) insisting they are "safe" and refusing to use condoms. References: Quinn TC, Wawer MJ, Sewankambo N, et al. Viral load and heterosexual transmission of human immunodeficiency virus type 1. N Engl J Med 2000;342:921-9.
Not so fast, Minerva! 17 February 2002
George Hill, Executive Secretary Doctors Opposing Circumcsion, Seattle Washington 98107, USA Send response to journal: Re: Not so fast, Minerva!	EDITOR--Minerva, goddess of wisdom, in her haste to report the latest opinion piece from another journal, apparently has forgotten that association does not prove causation.1 Bailey and colleagues rely on outmoded data to argue that there is an association between lack of male circumcision and HIV infection, and, therefore, male circumcision should be instituted as a prophylactic measure.2 de Vincenzi and Mertens, however, report that those early studies are filled with methodological flaws.3 More recent and better controlled studies do not support the conclusion that male circumcision is an effective disease control measure. Viral load4 and genital ulcers recently have emerged as the major factors in determining the risk of transmission of HIV.5 Older studies of the relationship between circumcision status and HIV infection do not control for viral load so their data are unreliable. Moreover, Gray et al., reporting from the Rakai Project, find that male circumcision is not a significant factor in HIV transmission.5 If it was true that is a significant association between high rates of HIV infection and lack of circumcision then one would expect to find that the corollary is also true--that there is a significant association between circumcision and low rates of HIV infection. However, that is not the case in America. Laumann et al. report that 78 percent of the U. S. adult males in their sample are circumcised.6 Laumann et al. also report that circumcised males are more likely to have a viral or bacterial STD infection. UNAIDS reports that the mostly circumcised United States has an adult HIV infection ratio of 0.61 as compared, for example, with the mostly intact United Kingdom, where few males are circumcised, which has an adult HIV infection ratio of 0.12.7 Bailey and colleagues admit that medical services in developing nations presently cannot provide safe circumcision services due to lack of sterile medical facilities.2 This lack of sterile facilities is confirmed by a recent report in the BMJ of HIV transmission in developing countries by sharps due to lack of sterilisation facilities,8 which is also yet another confounding factor in the study of the effect of male circumcision on HIV transmission. Gray et al. now believe that interventions to reduce viral load would be effective in reducing HIV transmission.5 Van Howe's recent meta-analysis concluded that proven methods of disease control only offer the best hope of controlling the epidemic.9 The evidence indicates that male circumcision is not a proven method of disease control.3,4,5,6,9 George Hill, Executive Secretary. Doctors Opposing Circumcision, 2442 NW Market Street, Suite 42, Seattle, Washington 98107, USA Web: http://faculty.washington.edu/gcd/DOC/ Minerva. BMJ 2002;324:374. Bailey RC, Muga R, Poulussen R, Abicht H. The acceptability of male circumcision to reduce HIV infections in Nyanza Province, Kenya. AIDS Care 2002;14(1):27-40. de Vincenzi I, Mertens T. Male circumcision: a role in HIV prevention? AIDS 1994;8(2): 153-160. Quinn TC, Wawer MJ, Sewankambo N, et al., for the Rakai Project Study Group. Viral load and heterosexual transmission of human immunodefficiency virus type 1. N Engl J Med 2000; 342: 921-29. Gray RH, Wawer MJ, Brookmeyer R, et al. Probability of HIV-1 transmission per coital act in monogamous, heterosexual, HIV-1-discordant couples in Rakai, Uganda. Lancet 2001; 357: 1149-53. Laumann, EO, Masi CM, Zuckerman EW. Circumcision in the United States. JAMA 1997;277(13):1052-1057. UNAIDS. Epidemiological Fact Sheets on HIV/AIDS and sexually transmitted infections. Geneva: UNAIDS, 2000. Gissellquist D, Rothenburg R, Potterat J, Drucker E. Non-sexual transmission of HIV has been overlooked in developing countries. BMJ 2002;324:235. Van Howe RS. Circumcision and HIV infection: review of the literature and meta-analysis. Int J STD AIDS 1999;10:8-16.