Natsal collects information not only on people’s health and wellbeing, but also their use of healthcare services. For example, Natsal-3 found that many young adults with a higher risk of chlamydia infection had not recently tested. These findings helped to evaluate whether the National Chlamydia Screening Programme was reaching populations most likely to benefit from testing.  

By identifying gaps between people’s needs and the support they receive, Natsal helps policymakers, health professionals, educators and charities understand where service improvements ae needed. 

Natsal is limited by the number of questions it can ask so as not to be too burdensome for participants. When reviewing the questionnaire at each round, there needs to be a careful balance between keeping questions from previous surveys to allow for comparisons over time and adding new questions so Natsal explores contemporary topics.   

To help ensure that Natsal findings are relevant and useful, Natsal researchers consult people who have an interest in Natsal findings, such as professionals and policymakers working in sexual health, to decide which questions should be added, updated or removed in order to collect the data most useful for informing policy and practice.   

For the development of the Natsal-4 questionnaire, an open online public consultation was held. There were 294 responses from members of the public, clinicians, policy makers, educators, researchers and those representing community and voluntary groups. These responses were used by the Natsal team to finalise which questions would be included or removed to ensure the final survey was an appropriate length.   

Some Natsal participants are asked to provide biological samples (for example urine or vaginal swabs). Combining information from biological samples with responses from survey questions allows Natsal to gain a fuller understanding of sexual health in Britain. For example, it enables a more accurate estimation of the prevalence of sexually transmitted infections in the population, as well as identifying which groups might not be accessing services. Information from Natsal can improve understanding of patterns of infection transmission and risk factors, which in turn can be used to inform and evaluate sexual health policies and screening services.  

For the first time, Natsal-4, asked individuals for permission to link their survey responses to information from their health, education and/or other administrative records. This is called data linkage. Examples include records held by General Practitioners (GPs), hospitals and education services. Linking information across sources can help researchers better understand the complex factors that influence sexual health and wellbeing throughout people's lives.  

Since the 1990s, Natsal has been funded primarily by the Wellcome Trust, a global charitable foundation which seeks to support research tackling pressing health challenges. Natsal-4 also received funding from the Economic and Social Research Council and the National Institute of Health Research.