Health messages telling people to change their lifestyles should be more upfront and less misleading about the benefits people can expect.
That’s the finding from a paper in the journal Nature Human Behaviour calling on health organisations like the NHS to be clearer and more honest about what they say.
The team from Brunel University London and the University of Oxford looked at public health messages on 2,500 English language websites worldwide.
Nearly half (45%) were from government organisations such as the NHS and CDC (Centers for Disease Control and Prevention). Fewer than one per cent specifically spell out how much changing a certain behaviour can benefit someone’s health.
“We tend to think health misinformation comes from online scams, but these are very reputable organisations the population trust,” said Dr Micheal de Barra.
“Institutions prioritise what they see as effective behaviour change over transparency. There seems a real unwillingness in public health to just be frank with people about how big or small the benefits of behaviour change are, or how settled the science is.”
Messages asking people to change their behaviours should quantify the size of expected benefits and harms, the writers urge. Understanding the size of the expected benefit, they argue is the only way people can balance health benefits against personal priorities.
Doctors try to give patients a full picture of the costs and benefits of a medical intervention. But public health information about drinking alcohol, weight loss or exercise rarely clarifies the size of expected health benefit and the strength of the science behind the claim. Breastfeeding, for example, may help cognitive development and prevent illness, but comes at a significant cost for mothers. Parents deciding on breastfeeding, the authors argue deserve clear estimates about the likely benefits. Time spent exercising, similarly, may mean people have less time to do other things they value such as seeing family or friends. There are important trade-offs.
An example of good health communication the study highlights is this from Bupa: ‘And after you hit 40, each additional year you smoke reduces your life expectancy by another three months.’ It clearly tells the reader what’s to gain from quitting. This compares with hazier instructions from the CDC: ‘Being physically active lowers your risk for developing several commonly occurring cancers,’ which says nothing about how much someone can reduce their risk. People need meaningful estimates of how much behaviour change can improve health, the writers urge.
“If there's uncertainty about how beneficial particular behaviour changes are, that's also something that is important to communicate,” says de Barra. “If the plausible range of benefits is very, very wide, that means there’s a shaky understanding of the phenomenon. And that's an important thing for people to understand as well.”
Navigating the next public health crisis depends on public trust in health communications and research, the study warns. Yet persistently exaggerating health benefits risks eroding confidence in public health messages, Dr de Bara says: “Public trust in public health organisations is very important. Being clearer about effect sizes, causality, and scientific certainty seems like a good way to be worthy of that trust.”