Thirty years of safer-sex advice were thrown into confusion at the 2010 International Microbicides Conference yesterday when a survey of lubricant use amongst a group of women and gay men found that those who used lubricants for anal sex were three times more likely to acquire gonorrhoea, chlamydia or syphilis than those who used none.
This effect was independent of the number of partners people had or how many times they had sex, and was also independent of whether they used condoms or not.
Researcher Pamina Gorbach of the University of California, Los Angeles, stressed that these results came from a small survey of a possibly unrepresentative group, and that her study was not powered to analyse the risk of various different lubricants. However, an accompanying study by Charlene Dezzutti of the University of Pittsburgh did find that some lubricants created more cellular damage than others.
These results imply that traditional messages about safer sex – "always use condoms and lube" - may have to be used with caution, at least until larger studies further investigate the apparent risk associated with lubricants and analyse which ones are the least harmful.
Gorbach’s survey was part of the U19 rectal microbicide research initiative funded by the US National Institutes of Health. Between October 2006 and December 2008, 879 men and women from the U19 programme completed computer-assisted self-interviews for the researchers about their sexual behaviour and were tested for rectal STIs – gonorrhoea, chlamydia and syphilis.
In order to include enough women who had had anal sex, half the interview group consisted of women who had had receptive anal intercourse (RAI) at least once in the last year, whereas gay men were only included if they had had RAI in the last month.
Just under half of the people interviewed (421 people, 47.6%) reported having had receptive anal sex within these criteria: 229 men having had it in the last month and 192 women in the last year. Of these, 302 completed the behavioural survey and all STI tests; the remaining data concern this group.
The group was 58% male and was a somewhat older group than many sex surveys, with a median age of about 40; 51% were African-American and the average socioeconomic status was poor, with 21% of the group classing themselves as homeless and 35% as disabled.
Three-quarters of the group (230 people) said they had used a lubricant during the last time they had had receptive anal intercourse. Lubricant use was less common in African-Americans (38.5%) and Hispanic people (58%). More HIV-positive people used a lubricant than HIV-negative people.
People used various kinds of lubricant: 67% had used a water-based one such as KY Jelly, 28% a silicone-based lubricant, 17% an oil-based lubricant such as Crisco, and 6% a numbing lubricant designed to deaden sensation.
One in twelve group members tested positive for a rectal STI (5.6% of women and 10.2% of men); only chlamydia and gonorrhoea were included in the analysis as syphilis is often transmitted orally.
Over one in nine (11.7%) of lubricant users were positive for a rectal STI compared with one in 22 (4.5%) who did not use lubricant: this was statistically significant (p=<0.05).
More than two-thirds (68%) of people diagnosed with rectal gonorrhoea and/or chlamydia had used a lube compared with a third of people who had not used a lube.
In multivariate analysis, using a lubricant was associated with a more than threefold greater risk of acquiring an STI (relative risk 3.15, 95% CI, 1.23 to 8.04). This was after controlling for number of partners, frequency of sex, condom use, gender and HIV status. In other words, lubricant use was not a surrogate marker for other risk behaviours but appeared to pose an independent risk. When syphilis was included in the analysis, the association of STIs with lubricant use was even stronger.
“What’s our take home message here?” Gorbach was asked. She said that her message would be that people should choose their lubricating substance carefully. Lubricants were not regulated like medicines: they were classed as ‘medical devices’ and did not have to undergo stringent safety testing. Many had ingredients that were ‘not friendly’ to the cells lining the rectum.
To underline this, another study (Russo) tested for toxicity six lubricants that can be bought over the counter in the USA. These were five water-based lubricants (Astroglide, Elbow Grease, ID Glide, KY Jelly and PRÉ vaginal lubricant) and one silicone-based one (Wet Platinum).
The physical properties of each lubricant were measured. Four lubricants (Astroglide, KY Jelly, ID Glide and Elbow Grease) were strongly hyperosmolar. This means that they would cause water to diffuse out of the cells lining the rectum into the rectum itself.
The lubes were tested on ‘friendly’ bacteria that are part of the normal vaginal flora. Astroglide killed off one species of Lactobacillus and KY Jelly, which contains the disinfectant clorhexidine, killed all species.
The four hyperosmolar lubricants stripped off the epithelium (outer layer) of cells from rectal tissue. In contrast, PRÉ and Wet Platinum caused relatively little damage. Astroglide caused almost as much damage as nonoxynol-9, the spermicide whose use has been shown to increase susceptibility to HIV.
As members of the audience commented, these studies do not imply that people should be advised not to use lubricant in anal sex, as this can cause trauma in itself. However, there is clearly an urgent need to conduct further research into sexual lubes, distinguish between harmful and harmless ones, and probably introduce more stringent safety checks for them before licensing them for over-the-counter sale.