Public Health Disrupted

Sex by numbers

Public Health Disrupted

Show Notes

“A remarkable number of claims you see in newspapers and magazines about sex are essentially made up.”

What does the average British person think about sex? For over 40 years the Natsal surveys have been recording sexual data, capturing striking changes in our behaviour and sexual lifestyles across the decades. They have been pivotal in the population measurement of the social, behavioural and biological aspects of sexual health. Its evidence has underpinned public health policy, practice and research for over 25 years.

So, how do you get someone to open up about something that’s so deeply personal and sensitive? Who decides what questions need to be asked and how much can we rely on the reported data? As a co-lead at Natsal, Prof Cath Mercer shares insights into the methodology and the survey’s broadening remit while Professor Sir David Spiegelhalter presents his argument for disrupting public health messaging.

GUESTS Professor Cath Mercer is Professor of Sexual Health Science at UCL and co-lead of UCL’s Centre for Population Research in Sexual Health and HIV. A statistician and demographer by training, Cath is recognised internationally as an expert in developing and employing robust methods that advance the study of sexual behaviour - one of the most socially-sensitive areas of scientific inquiry. For more than 20 years, Cath has played a key role in delivering Britain’s National Survey of Sexual Attitudes and Lifestyles (Natsal), one of the largest and most comprehensive surveys on sexual health in the world. She is now co-leading the fourth Natsal. Cath also champions myth-busting and promoting the public conversation around sex, including - rather nerve-wrackingly - through stand-up comedy sets for UCL’s Bright Club and her TEDx talk ‘Let's talk about (real) sex’. Professor Sir David Spiegelhalter is Emeritus Professor of Statistics in the Centre for Mathematical Sciences at the University of Cambridge. He was previously Chair of the Winton Centre for Risk and Evidence Communication, which aimed to improve the way that statistical evidence is used by health professionals, patients, lawyers and judges, media and policy-makers. He was very busy over the Covid crisis. He presented the BBC4 documentaries “Tails you Win: the Science of Chance”, the award-winning “Climate Change by Numbers”. His bestselling book, The Art of Statistics, was published in March 2019, and Covid by Numbers came out in September 2021. His career highlights include appearing on Desert Island Discs in 2022, and in 2011 coming 7th in an episode of BBC1’s Winter Wipeout. Find out more about the NatSal Surveys on their website https://www.natsal.ac.uk/ Production Credits: Public Health Disrupted with Rochelle Burgess and Xand van Tulleken is a podcast from UCL Health of the Public. Recorded remotely and edited by Annabelle Buckland at Decibelle Creative / @decibelle_creative.

More from Public Health Disrupted

Sep 17, 2026

From the moment we are born, microbes begin to shape our development. But what role do these early microbial communities play in our long-term health? In this episode, Professor Rochelle Burgess is joined by Professor Meghan Azad and UCL Professor Nigel Field to explore the science of the infant microbiome and what it can teach us about lifelong health.

Aug 3, 2026

To mark UCL's bicentenary, Public Health Disrupted comes to a live audience for the very first time. Hosts Xand van Tulleken and Rochelle Burgess are joined by medical historian Dr Cristiano Turbil for a conversation that challenges some of the stories we tell about public health progress.

Jul 15, 2026

Xand van Tulleken and Rochelle Burgess explore a deceptively simple question: what role does love play in our health and wellbeing?

Jun 11, 2026

Global Mental Health: Rights, Care and the Global Landscape

Apr 21, 2026

In the first episode of Season 6 of Public Health Disrupted, Dr Xand van Tulleken and Professor Rochelle Burgess explore why younger generations are drinking less, and what that shift means for public health.

See all episodes →