One in six people living in Calderdale suffer from back pain, figures show, with a charity warning it can have a "devastating impact" on quality of life.
Newly-released analysis by Imperial College London shows that 36,384 people in Calderdale reported suffering from back pain in 2012.
That's 18 per cent of the population, slightly higher than the England average of 17 per cent.
The data was collected from Public Health England's Health Survey, and analysed by Imperial College for the charity Versus Arthritis.
Only people who were in pain at the time of the survey, and had been in pain for at least three months, were counted in the figures.
That means the data is likely to be an underestimate of the prevalence of the condition, since acute bouts of back pain can be resolved within a three-month period.
More than 60 per cent of declared sufferers in Calderdale reported having severe back pain - a total of 22,686 people.
Back pain is the largest single cause of disability in the UK, and about 80 per cent of adults will experience it at some point in their lifetime.
A spokesperson for Versus Arthritis said: "Back pain can have a devastating impact on people's lives, affecting their independence, mobility, and ability to stay in work.
"Whilst there are currently a number of ways to manage this pain, such as physiotherapy and painkillers, the high prevalence highlights the need for more investment into treatments and better pain management techniques.
"We urge anyone struggling to manage their pain to speak to a healthcare professional about the best options for them, or contact us for self-management advice."
Across England, more than 9 million people live with back pain, and 5.5 million with severe pain.
Nuzhat Ali, national lead for musculoskeletal conditions at PHE, said: "Musculoskeletal conditions, such as back pain, are the biggest cause of lost working days in England, after coughs and colds.
"Our sedentary lifestyles, ageing population, high obesity rates and reduced levels of physical activity mean these conditions will continue to rise.
"We're working with partners to help everyone, including employers, to play their part in reducing this."