Smokers may be at greater risk of HIV infection than non-smokers, reveals an analysis of published research issued ahead of print in the journal Sexually Transmitted Infections.

Cigarette smoking has already been linked to a higher than normal chance of contracting other infections generally, including those that have been sexually transmitted.

The researchers trawled through 13 academic research databases, three abstract databases from recent international AIDS conferences, as well as viewing relevant websites and contacting experts in the field.

Six studies assessed the association between cigarette smoking and becoming HIV positive. Five of them concluded that smokers ran a greater risk of this varying from around 60% to a more than tripling of the risk.

Ten further papers looked at the association between smoking and progression to AIDS, nine of them concluding that smokers were not at increased risk.

“The consistency of the findings is striking and represents a major strength of this review,” comment the authors, adding: “while the studies vary in quality, they include reports of high quality investigations using large sample sizes.”

Tobacco smoke may enhance vulnerability to infection by modifying the structure of the lungs and changing an array of immune system responses, including curbs on the production of antibodies and the activity of infection fighting white cells, say the authors.

There are almost 40 million people in the world living with HIV/AIDS, and the global death toll of deaths related to tobacco is expected to reach 8.4 million in 2020.

The authors suggest that as well as encouraging people to give up smoking as an essential public health measure, this may also contribute to the effectiveness of HIV/AIDS prevention programmes.