Many countries are not preparing themselves for the huge health impact of an increasing elderly population, says the World Health Organisation (WHO).

Developing countries are particularly unprepared for the explosion of elderly people likely in the next century.

Combined with growing life expectancy is a reduction in birth rates throughout the world.

This means there will be fewer people to look after the elderly and fewer people in the workforce to support them financially.

The WHO says already more than a half of the 580m people over 60 - some 355m - live in developing countries.

Speed

The speed of the increase in average life expectancy is much faster than in developed countries.

It has taken France some 115 years for the proportion of people over 60 to double from seven to 17%.

However, it is thought that the elderly population in China could double between 2000 and 2027 - just 27 years.

The average life expectancy in developing countries has risen from 41 years in the early 1950s to 62 years in 1990.

By 2020, it is expected to rise to 70 years.

Already more than 20 developing countries have a life expectancy of 72 years or higher.

These include Sri Lanka, Jamaica and Cuba.

In most countries, excluding sub-Saharan Africa, birth rates have also fallen greatly.

Oldest region

However, despite projections that the number of elderly people in the world will reach more than 1bn by 2020 with 700m of them being in developing countries, Europe will still retain its title of oldest region in the world.

By 2020, a quarter of all Europe's residents will be over 60.

But Japanese people will live longest. Thirty-one per cent of its residents will be over 60 by 2020.

However, Greece and Italy narrowly pip Japan for the number of people expected to live past 80.

Age-related disease

The health impact of living longer is likely to be huge.

Three quarters of all deaths could be age-related by 2020, says the WHO.

Deaths from circulatory disease are rising around the globe

Most of the deaths will be due to circulatory problems such as heart disease, diabetes and cancer.

In Latin America, the number of age-related diseases is rising already.

In Argentina, Cuba and Uruguay, circulatory problems and cancer are responsible for 60% of all deaths.

In Africa, diabetes and hypertension are on the increase in several countries, including South Africa.

And in Asia, cancer and circulatory problems are the leading causes of deaths and diabetes has reached developed country proportions.

The WHO says circulatory problems cost the US $153bn a year in 1996, including medical treatment and loss of earnings.

Around 8% of developed countries' health budgets is eaten up by diabetes.

Dementia

And then there is mental health. The number of people with senile dementia in Africa, Asia and Latin America is likely to double to over 55m by 2020.

"The emerging social and public health consequences of ageing, especially in developing countries, need to be taken very seriously," says the WHO.

"In the majority of these countries poverty, lack of social security schemes, continuing urbanisation and the growing participation of women in the workforce all contribute to the erosion of traditional forms of care for older people."

It fears many countries are not ready to face up to the speed with which the ageing problem will hit them and its public health consequences.

It adds that many are facing the "double burden" of having to plan for a big increase in age-related diseases as well as a huge number of communicable diseases, such as Aids.

Health programme

The organisation launched a new programme on ageing and health in April 1995.

It will look at improving information on the effects of ageing on health, developing community-based programmes, training health workers and creating affordable and effective policies to deal with the problem.

"Living longer is both an achievement and a perpetual challenge. Investing in health and promoting it throughout the life span is the only way to ensure that more people will reach old age in good health and capable of contributing to society intellectually, spiritually and physically," it says.