Commercially available sexual lubricants may increase people’s susceptibility to sexually transmitted infection (STIs), US scientists reported recently. A study found that people who consistently used shop-bought ‘lubes’ for anal sex were three times more likely to have an STI than people who did not.
The study1 confirms results announced at the 2010 International Microbicides Conference. It found that people who had consistently used commercially available lubricants while being the passive partner in anal sex over the last month (the last year if female) were three times more likely to test positive for syphilis, rectal gonorrhoea or chlamydia than people who had not.
The study took a mixed population of women and gay men and asked them whether they had had receptive anal sex in the last year and month, whether they had used commercially sold lubes and, if so, what kind: were they water-based (e.g. KY), silicone-based (e.g. ID Millennium) or oil-based (e.g. Crisco). They also tested participants for rectal chlamydia and gonorrhoea with a swab and took a blood test for syphilis.
Because women tended to have anal sex only occasionally, one important distinction was that the definition of regular receptive anal sex was ‘during the last month’ for the men but ‘during the last year’ for the women.
The average age of participants was 39; 46% were women and 54% gay men. HIV status varied by age: 14% of 18 to 25 year-olds had HIV versus 37% of 26 to 35 year-olds. Over half (53%) were African-American, 18% Hispanic and 23% white.
The advice still stands that using condoms plus silicone- or water-based lube is the best way to avoid STIs.
Very few people reported one-off or casual anal intercourse: only 5% of people reported they had had a one-off sexual encounter involving anal sex during the last month (last year if a woman). In contrast, 56% reported anal sex during the last month (last year if a woman) with a main partner.
Only 12% of participants had not used commercially purchased lube at all, but only 32% of participants had used lube every time they had anal sex (the ‘consistent lube users’). One important caveat is that neither the sachets of lube supplied with free condoms, nor ad hoc lubes like hand cream, were counted in this survey: it only concerned lubes bought over the counter.
There were differences between consistent lube users and other participants. Lube users were nearly twice as likely to have HIV if they were under 35, though not if they were older. African-Americans were less likely than average to be consistent lube users and Hispanics more so. There were no differences between lube users and non-users in the number of partners they had or how many times they had anal sex.
The survey found that 9.5% of consistent lube users had an STI versus 2.9% of inconsistent/non-users (three times more). This was statistically significant and these results were independent of people’s age, race, gender, HIV status, number of partners and amount of sex.
Understanding condom use is problematic, because, while participants were asked about whether they had had receptive anal sex and/or used lube over the last month, they were only asked whether they had used condoms the last time they had anal sex. So we cannot say, for instance, whether people who used condoms the last time they had sex had more or fewer partners, or had sex more or less often, than people who hadn’t used condoms.
Nonetheless, in univariate analysis (i.e., not taking other factors into account), condom use at last sex was not significantly protective against STIs: 4.6% who reported condom use last time they had anal sex had an STI compared with 5.1% of those who did not report condom use - not a statistically significant difference. This doesn’t necessarily mean that condoms don’t protect against STIs. It could mean that, because condom users were more likely to use lube (44% used lube versus 24% of those who didn’t use condoms), the protective effect of condoms was being eroded by a harmful effect of the lubricant used. It could mean that condom users had more anal sex, but we don’t know.
The type of lube didn’t make a difference. One theory2 is that water-based lubes draw water out of the cells lining the rectum and damage them; silicone-based lubes might be safer, and even oil-based lubes for people not using condoms. However, in this study, although figures are small because few people exclusively used one type of lube, STIs were more common in consistent users of silicone lubes as well as of water-based ones.
The reason for these findings is unknown, but has left prevention workers at a loss as to what to say about lubes. It does not show that people should stop using lubes and at present the advice still stands that using condoms plus silicone- or water-based lube is the best way to avoid STIs. No causation has been proven: the study could not show how long participants had had STIs and so can’t reliably relate them to the times lube was used. Nonetheless this study, plus another3 that showed most commercially available lubes damage rectal cells to some extent, makes more research into lubricants and to how people use them in anal sex an urgent priority.
