Approximately 2.3 billion people around the world - nearly half of all adults over the age of 20 - will experience at least one lower urinary tract symptom, such as adult incontinence, by 2018, new research suggests.

The study, which is published in the urology journal BJUI, provides detailed forecasts for North and South America, Africa, Asia and Europe.

It suggests that the prevalence of lower urinary tract symptoms, overactive bladder and urinary incontinence will increase by 18 per cent around the world in the space of just ten years.

South America, Asia and developing countries in Africa are likely to be particularly affected by an increase in adult incontinence, with many people relying on products such as Tena Lady as they get older.

Lead author Dr Debra Irwin, from the University of North Carolina's department of epidemiology, said: "Our study suggests that urinary and bladder symptoms are already highly prevalent worldwide and that these rates will increase significantly as the population ages.

"These findings raise a number of important worldwide issues that will need to be tackled, as a matter of urgency, by clinicians and public health experts if we are to prevent and manage these conditions."

The study collated data on the numbers and prevalence of adults with urinary and bladder conditions in 2008, using population estimates from the US Census Bureau International Database and a large population-based survey called the Epic study.

Researchers then extrapolated the figures and calculated that the worldwide prevalence of overactive bladder will increase by 20 per cent between 2008 and 2018, with 546 million people set to be affected.

At the same time, the prevalence of urinary incontinence will increase by 22 per cent and the condition will affect some 423 million people.

Dr Irwin said there is an "urgent need" to increase awareness of adult incontinence and other urinary and bladder complaints, as well as to improve their prevention, diagnosis and management.

She concluded that international and national programmes aimed at increasing public awareness, educating doctors and implementing public health campaigns to tackle the stigma associated with these conditions "will be a significant step towards reaching this objective".