The accuracy of reported sensitive sexual behaviour in Britain: exploring the extent of change 1990-2000.

OBJECTIVES: The 1990-1 British national probability sample survey of sexual attitudes and lifestyles (Natsal 1990) was repeated in 1999-2001 (Natsal 2000) to update population estimates of risk behaviours, and assess change over time. We examine whether changes in prevalence estimates may partly result from changes in measurement accuracy. METHODS: Taking Natsal 2000 (11 161 respondents) and Natsal 1990 (13 765 respondents aged 16-44) we compared the response rate, sample representativeness, reporting of abortion last year (relative to official statistics), and selected attitudes. Among the common birth cohort eligible for both surveys (aged 16-34 Natsal 1990, 26-44 Natsal 2000), we compared reporting of experiences before 1990. RESULTS: The response rate (66.8% Natsal 1990, 65.4% Natsal 2000) and completeness of reporting abortion were unchanged (84% Natsal 1990, 86% Natsal 2000). Attitudes were significantly changed in Natsal 2000 relative to Natsal 1990--for example, increased tolerance of male homosexual sex, OR (95% CI) 2.10 (1.93-2.29) men and 2.95 (2.74 to 3.18) women. In the common birth cohort reporting of heterosexual intercourse before 16 (OR 1.15 (1.02 to 1.29) men, 1.49 (1.31 to 1.69) women), and homosexual experience (OR 1.80 (1.46 to 2.21) men, 2.00 (1.61 to 2.48) women) were significantly increased. CONCLUSIONS: The results are consistent with improved reporting accuracy for some sensitive behaviours in Natsal 2000, in line with greater social tolerance and improved survey methodology. However, the evidence is not conclusive, and may not be generalisable to all such behaviours. The increase found in the reported prevalence of STI risk behaviours between Natsal 1990 and Natsal 2000 is likely to be somewhat overstated.

Sexual behaviour in Britain: partnerships, practices, and HIV risk behaviours.

BACKGROUND: Sexual behaviour is a major determinant of sexual and reproductive health. We did a National Survey of Sexual Attitudes and Lifestyles (Natsal 2000) in 1999-2001 to provide population estimates of behaviour patterns and to compare them with estimates from 1990-91 (Natsal 1990). METHODS: We did a probability sample survey of men and women aged 16-44 years who were resident in Britain, using computer-assisted interviews. Results were compared with data from respondents in Natsal 1990. FINDINGS: We interviewed 11161 respondents (4762 men, 6399 women). Patterns of heterosexual and homosexual partnership varied substantially by age, residence in Greater London, and marital status. In the past 5 years, mean numbers of heterosexual partners were 3.8 (SD 8.2) for men, and 2.4 (SD 4.6) for women; 2.6% (95% CI 2.2-3.1) of both men and women reported homosexual partnerships; and 4.3% (95% CI 3.7-5.0) of men reported paying for sex. In the past year, mean number of new partners varied from 2.04 (SD 8.4) for single men aged 25-34 years to 0.05 (SD 0.3) for married women aged 35-44 years. Prevalence of many reported behaviours had risen compared with data from Natsal 1990. Benefits of greater condom use were offset by increases in reported partners. Changes between surveys were generally greater for women than men and for respondents outside London. INTERPRETATION: Our study provides updated estimates of sexual behaviour patterns. The increased reporting of risky sexual behaviours is consistent with changing cohabitation patterns and rising incidence of sexually transmitted infections. Observed differences between Natsal 1990 and Natsal 2000 are likely to result from a combination of true change and greater willingness to report sensitive behaviours in Natsal 2000 due to improved survey methodology and more tolerant social attitudes.

Sexual behaviour in Britain: early heterosexual experience.

BACKGROUND: Relatively high rates of teenage conception and sexually transmitted infection among young people in Britain have focused attention on early sexual behaviour and its determinants. We report the results of the second National Survey of Sexual Attitudes and Lifestyles (Natsal 2000). METHODS: We did a probability sample survey between 1999 and 2001, of men and women aged 16-44 years in Britain. Participants were interviewed using a combination of computer-assisted face-to-face and self-completion questionnaires, and asked questions regarding first heterosexual intercourse, communication about sex, pregnancy, and sexually transmitted infections (STIs). FINDINGS: We recruited 11161 men and women to the survey (4762 men, 6399 women). The proportion of those aged 16-19 years at interview reporting first heterosexual intercourse at younger than 16 years was 30% for men and 26% for women; median age was 16 years. The proportion of women reporting first intercourse before 16 years increased up to, but not after, the mid-1990s. There has been a sustained increase in condom use and a decline in the proportion of men and women reporting no contraceptive use at first intercourse with decreasing age at interview. Among 16-24 year olds, non-use of contraception increased with declining age at first intercourse; reported by 18% of men and 22% of women aged 13-14 years at occurrence. Early age at first intercourse was significantly associated with pregnancy under 18 years, but not with occurrence of STIs. Low educational attainment was associated with motherhood before 18 years, but not abortion. INTERPRETATION: The increase in the proportion of women reporting first intercourse before age 16 years does not appear to have continued throughout the past decade. Only a small minority of teenagers have unprotected first intercourse, and early motherhood is more strongly associated with educational level than with family background. Factors most strongly associated with risk behaviour and adverse outcomes have considerable potential for preventive intervention.

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 of sexual attitudes and lifestyles (Natsal 2000) in Britain, we estimated the frequency of self-reported STIs, and the prevalence of urinary Chlamydia trachomatis infection. METHODS: We did a stratified probability sample survey of 11161 men and women aged 16-44 years in Britain. Computer assisted self-interviews contained items on the nature and timing of previously diagnosed STIs. Half of all sexually 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 trachomatis. 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 among men aged 25-34 (3.1%) and women aged 16-24 years (3.0%). Non-married status, age, and reporting partner concurrency or two or more sexual partners in the past year were independently associated with infection with C trachomatis. INTERPRETATION: We show substantial heterogeneity in distribution of reported STIs, and the demographic and behavioural determinants of prevalent genital chlamydial infection. The results have potentially wide application for proposed chlamydia screening programmes which, given the demonstrated prevalence, must now proactively seek to involve men.

Effect of computer-assisted self-interviews on reporting of sexual HIV risk behaviours in a general population sample: a methodological experiment.

OBJECTIVES: To develop methods to maximize the accuracy of reporting HIV risk behaviours in a general population survey. We assessed the feasibility of using a computer-assisted self-completion interview (CASI) in comparison with pen-and-paper self-completion interview (PAPI). DESIGN: A probability sample survey of residents aged 16-44 years in Britain, with alternate assignment of addresses to interview by CASI (462) or PAPI (439). METHODS: Personal interviews exploring demographic and sexual behaviour variables. Principal outcome measures were the impact of CASI in relation to PAPI on data quality and rates of reporting a range of behaviours. RESULTS: A total of 901 interviews were completed; 829 individuals were eligible for and accepted the self-completion module. Internal consistency of data items was greater with CASI than PAPI and item non-response was lower. Overall, there was no significant difference in rates of reporting between CASI and PAPI. The main effect for CASI compared with PAPI in a generalized estimating equation (GEE) analysis was an OR (95% CI) of 1.04 (0.92-1.17). Variables were also examined individually, including homosexual partnership (adjusted OR 1.26 95%, CI 0.69-2.29), payment for sex (adjusted OR 0.68 95% CI 0.29-1.59), masturbation (adjusted OR 0.89 95% CI 0.66 1.22) and five or more partners in the past 5 years (OR 0.85 95% CI 0.61 -1.19). CONCLUSION: We found no evidence of a consistent effect of CASI on rates of reporting sexual HIV risk behaviours in this sample. CASI resulted in improvement in internal consistency and a reduction in missed questions.