Washington, Nov 6 (IANS): As people across the world live longer, soaring levels of chronic illness and diminished well being are poised to become a major global public health challenge, researchers have warned.

Unless health systems find effective strategies to address the problems faced by an ageing world population, the growing burden of chronic disease will greatly affect the quality of life of older people, said a major new series on health and ageing published in The Lancet.

By 2020, for the first time in history, the number of people aged 60 years and older will outnumber children younger than five years.

By 2050, the world's population aged 60 years and older is expected to reach two billion, up from 841 million today and 80 percent of these older people will be living in low-income and middle-income countries.

"Deep and fundamental reforms of health and social care systems will be required. But we must be careful that these reforms do not reinforce the inequities that drive much of the poor health and functional limitation we see in older age," suggested John Beard, director of the department of ageing and life course at the World Health Organisation (WHO).

Although, people are living longer, they are not necessarily healthier than before - nearly a quarter (23 percent) of the overall global burden of death and illness is on people aged over 60.

Much of this burden is attributable to long-term illness caused by diseases such as cancer, chronic respiratory diseases, heart disease, musculo-skeletal diseases (such as arthritis and osteoporosis), and mental and neurological disorders.

"This long-term burden of illness and diminished well being affects patients, their families, health systems and economies and is forecast to accelerate.

For example, latest estimates indicate that the number of people with dementia is expected to rise from 44 million now to 135 million by 2050.

"Collectively, we need to look beyond the costs commonly associated with ageing to think about the benefits that an older, healthier, happier and more productive older population can bring to society as a whole," said Somnath Chatterji from the department of health statistics and information systems at WHO.