Abstract

Objectives: To compare the characteristics of a self-selected, convenience sample of men who have sex with men (MSM) recruited through the Internet with MSM drawn from a national probability survey in Britain.

Methods: The Internet sample (n=2,065) was recruited via two popular websites for gay men in Britain in May and June 2003. This sample was compared with MSM (n=117) from the National Survey of Sexual Attitudes and Lifestyles (Natsal), a probability sample survey of adults resident in Britain conducted between May 1999 and February 2001.

Results: There were no significant differences between the samples on a range of socio-demographic and behavioural variables (p>0.05). However, men in the Internet sample were younger (p<0.0001), more likely to be students (p=0.0004) but less likely to live in London (p=0.0001) or report good health (p=0.014). While both samples were equally likely to report testing for HIV, men in the Internet sample were more likely to report a sexually transmitted infection in the past year (16.9% vs 4.8%, adjusted odds ratio: 4.14, 95% CI 1.76, 9.74, p=0.001), anal intercourse (76.9% vs 63.3%, p=0.001) and unprotected anal intercourse in the past three months (45.0% vs 36.6%, p=0.064).

Conclusions: The Internet provides a means of recruiting a self-selected, convenience sample of MSM whose social and demographic characteristics are broadly similar to those of MSM drawn from a national probability survey. However, estimates of high risk sexual behaviour based on Internet convenience samples are likely to overestimate levels of sexual risk behaviour in the wider MSM population.