People who walk slow and are a normal weight could be almost 2.5 times more likely to develop severe Covid-19 and 3.75 times more likely to die from the virus than normal-weight fast walkers.
The study, published in the International Journal of Obesity, looked at the relative association of body mass index (BMI) and self-reported walking pace with the risk of contracting severe Covid-19 and mortality among 312,596 middle-aged UK Biobank participants.
Those who walked at a speed of less than three miles per hour were considered to be slow walkers, while a steady/average spee was three to four miles per hour and a brisk walk being more than four miles per hour.
"We know already that obesity and frailty are key risk factors for Covid-19 outcomes,” said Tom Yates, lead researcher for the study and a professor of physical activity, sedentary behaviour and health at the University of Leicester.
"This is the first study to show that slow walkers have a much higher risk of contracting severe Covid-19 outcomes, irrespective of their weight.
"With the pandemic continuing to put unprecedented strain on healthcare services and communities, identifying individuals at greatest risk and taking preventative measures to protect them is crucial."
The research suggested normal weight slow walkers are more at risk of both severe disease and death than fast walkers with obesity.
Furthermore, risk was uniformly high in normal weight slow walkers and slow walkers with obesity.
Professor Yates added: "Fast walkers have been shown to generally have good cardiovascular and heart health, making them more resilient to external stressors, including viral infection, but this hypothesis has not yet been established for infectious disease.
"Whilst large routine database studies have reported the association of obesity and fragility with Covid-19 outcomes, routine clinical databases do not currently have data on measures of physical function or fitness.
"It is my view that ongoing public health and research surveillance studies should consider incorporating simple measures of physical fitness such as self-reported walking pace in addition to BMI, as potential risk predictors of Covid-19 outcomes that could ultimately enable better prevention methods that save lives."
The study was conducted by researchers from the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre.
The researchers noted a number of limitations to their study, saying although self-reported walking pace has been shown to be associated with cardiorespiratory fitness within UK Biobank, it is subject to possible reporting bias.
They say that given this and the observational design, no definitive causal conclusions can be derived from their results.
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