Sexual behaviour in Britain: reported sexually transmitted infections and prevalent genital Chlamydia trachomatis infection

Background Studies of the epidemiology of sexually transmitted infections ( STI) are largely based on surveillance data. As part of a national survey o f sexual attitudes and lifestyles (Natsal 2000) in Britain, we estimated th e frequency of self-reported STIs, and the prevalence of urinary Chlamydia trachomatis infection. Methods We did a stratified probability sample survey of 11 161 men and wom en aged 16-44 years in Britain. Computer assisted self-interviews contained items on the nature and timing of previously diagnosed STIs. Half of all s exually experienced respondents aged 18-44 years were invited to provide a urine sample for ligase chain reaction testing for C trachomatis infection. Findings 10.8% of men and 12.6% of women reported ever having an STI, 3.6% of men and 4.1% of women reported ever being diagnosed with genital warts, and 1.4% of men and 3.1% of women reported previous infection with C tracho matis. 76% of men and 57% of women ever diagnosed with an STI had been to a GUM clinic. C trachomatis was found in 2.2% (95% CI 1.5-3.2) of men and 1. 5% (95% CI 1.11-2.14) of women with age-specific prevalence being highest a mong men aged 25-34 (3.1%) and women aged 16-24 years (3.0%). Non-married s tatus, age, and reporting partner concurrency or two or more sexual partner s in the past year were independently associated with infection with C trac homatis. Interpretation We show substantial heterogeneity in distribution of reporte d STIs, and the demographic and behavioural determinants of prevalent genit al chlamydial infection. The results have potentially wide application for proposed chlamydia screening programmes which, given the demonstrated preva lence, must now proactively seek to involve men.