Wearing face coverings does not appear to lead people to abandon hand hygiene, researchers say, suggesting people may not trade off the benefits of one public health measure against another.
Face coverings are now mandatory in many parts of the world, and in England must be worn not only on public transport but also in many shops.
While there is little evidence that cloth face coverings protect the wearer from Covid-19, experts say a growing body of research suggests they help to reduce transmission, limiting its spread from wearers to others.
Some scientists have raised concerns that the use of face coverings could give wearers a false sense of security and make them less likely to engage in other behaviours that could reduce the spread of coronavirus, such as handwashing and social distancing – a phenomenon known as “risk compensation”.
However, researchers say they have looked at existing studies and found little sign that wearing masks reduces adherence to hand hygiene.
Writing in the journal BMJ Analysis, the team report how they looked at 22 systematic reviews exploring the impact of mask wearing on the rate of respiratory viruses other than Covid-19, including flu, finding within them six randomised controlled trials that also looked at hand hygiene.
“We don’t have any direct evidence from the current pandemic, so all we have done is look at ‘well what existing evidence is there?’” said Prof Dame Theresa Marteau, a co-author of the research from the University of Cambridge.
While the six studies were not specifically designed to look at whether wearing masks influenced handwashing, the team say none showed evidence that mask-wearing was linked to a reduction in hand hygiene – as measured by self report and also, in four of the studies, by the volume of soap or sanitiser used. Indeed two of the studies suggested mask-wearing may even increase hand hygiene.
Marteau said while the research only covered six studies, the results chimed with other research, also highlighted by the team, that found no clear evidence that interventions such as the use of helmets when skiing or cycling increased risky behaviours.
“That’s not to say risk compensation doesn’t exist – it certainly exists at an individual level … But we can’t find any good evidence for risk compensation happening at a population level,” she said.
She said there was no sign that wearing face coverings increased transmission of Covid-19, as may be expected if risk compensation was rife.
“The concept of risk compensation, rather than risk compensation itself, seems the greater threat to public health through delaying potentially effective interventions,” the team wrote.
Trish Greenhalgh, a professor of primary care health sciences at the University of Oxford, welcomed the study.
“Many leading scientists and policymakers, including the UK government and the World Health Organization, used the idea of risk compensation as a reason to block the implementation of an intervention – face coverings – that could have saved many lives if implemented earlier,” she said. “[This research] is shocking because it reveals the confidence with which these bodies made claims that had no basis in fact.”
Dr Julian Tang, an honorary associate professor in respiratory sciences at the University of Leicester, said the research was important in raising awareness of the “myth” of risk compensation for mask-wearing.
“Whilst the authors accept that individual variation is possible, the overall impact of mask-wearing to the population is more likely to be more beneficial than not,” he said.
However, some warn there has been little research into people’s behaviour regarding actions such as mask-wearing and social distancing – or how different behaviours influence each other – and it is not clear how the team picked the studies.
Robert Dingwall, a professor of sociology at Nottingham Trent University, was among those sounding a note of caution: “It certainly seems premature to claim that risk compensation theory has been ‘laid to rest’ or that the concern should not be taken seriously in better-designed and more balanced studies of this intervention.”