According to a UN report, governments around the world must work out how to cope with ageing. The study by the UN Population Fund (UNFPA) and private group HelpAge International also urged countries to improve medical provision to extend the years of health that older people can enjoy.
The report, which was released to coincide with International Day of Older Persons, says that of the seven billion people who live on the planet, 893 million or 12.8 percent are elderly -- older than 60.
In just one decade, the elderly population will swell by 200 million taking it well beyond one billion people, and potentially putting a greater strain on welfare and medical systems around the world, the report said.
The report was accompanied by a symposium on ageing in Japan, the world's fastest-greying country, where around a quarter of the population is over 65 already, a proportion the government forecasts will rise to 40 percent within half a century.
"People everywhere must age with dignity and security, enjoying life through the full realization of all human rights and fundamental freedoms," said Babatunde Osotimehin, UNFPA executive director.
By 2050, the report said, some 80 percent of the world's older people will live in developing countries, many of which currently have young populations where there are many more workers than pensioners.
"In many developing countries with large populations of young people, for example, the challenge is that governments have not put policies and practices in place to support their current older populations or made enough preparations for 2050," the groups said in a joint statement.
The report warned that the skills and knowledge older people possess are going to waste, with many elderly under-employed and vulnerable to discrimination, abuse and violence at work and in the home.
The agencies are calling for governments and the public to end "these destructive practices and to invest in older people".
"We must commit to ending the widespread mismanagement of ageing," said Richard Blewitt, chief executive officer of HelpAge International.
"Global and national action plans are needed to create a pathway (so) people over 60... become growth drivers and value creators," he said.