The study by Robert C. Bollinger and colleagues from Johns Hopkins University Medical School and the National AIDS Research Institute in Pune, India, was published Friday as a "research letter" in The Lancet medical journal.
"It is now about the ninth study which followed men who are HIV-negative over a period of months or years. It is the ninth study in a row which has found that the effect (of circumcision) is significant," said Robert C. Bailey, professor of epidemiology and biostatistics at the University of Illinois at Chicago, who was not connected with Bollinger's study.
"The fact that they found no behavioral differences between the two groups is all the more compelling, and indicates that there is a biological factor," Bailey said in a telephone interview.
Bailey, like the authors of the Lancet study, believe that cells in the foreskin may be particularly susceptible to infection.
The association between circumcision and a reduced risk ofwas noted as early as 1987, when Dr. William Cameron of the University of Manitoba in Canada reported findings from a study in Kenya.
The research published in The Lancet tracked 2,298 men who were being treated at three clinics in Pune, and who were confirmed to be HIV-negative at the start of the study.
The study also found that circumcised men were as much atof , and as the uncircumcised.
The nine studies have all tried to control for variables in behavior, Bailey said. "A randomized control trial is what is necessary now to really nail this down," he said.
By Robert Barr