Methodology of the third British National Survey of Sexual Attitudes and Lifestyles (Natsal-3).

BACKGROUND: Data from the first two National Surveys of Sexual Attitudes and Lifestyles, carried out in 1990-1991 (Natsal-1) and 1999-2001 (Natsal-2), have been extensively used to inform sexual health policy in Britain over the past two decades. Natsal-3 was carried out from September 2010 to August 2012 in order to provide up-to-date measures of sexual lifestyles and to extend the scope of the previous studies by including an older age group (up to 74 years), an extended range of topics and biological measures. METHODS: We describe the methods used in Natsal-3, which surveyed the general population in Britain aged 16-74 years (with oversampling of younger adults aged 16-34 years). RESULTS: Overall, 15 162 interviews were completed, with a response rate of 57.7% and a cooperation rate of 65.8%. The response rate for the boost sample of ages 16-34 years was 64.8%, only marginally lower than the 65.4% achieved for Natsal-2, which surveyed a similar age range (16-44). The data were weighted by age, gender and region to reduce possible bias. Comparisons with census data show the weighted sample to provide good representation on a range of respondent characteristics. The interview involved a combination of face-to-face and self-completion components, both carried out on computer. Urine samples from 4550 sexually-experienced participants aged 16-44 years were tested for a range of STIs. Saliva samples from 4128 participants aged 18-74 years were tested for testosterone. CONCLUSIONS: Natsal-3 provides a high quality dataset that can be used to examine trends in sexual attitudes and behaviours over the past 20 years.