Mrs Bani Gupta of Calcutta became depressed when her husband died. But she decided to join a women's association, and slowly emerged from her depression. "So many women came with such serious problems that my own crisis seemed insignificant," she says. She's just one of nearly 600 million people aged 60 and over in the world today, and India has more than any other country. The numbers have grown for good reasons - because of medical advances and improvements in nutrition which have led to longer life expectancy, even in poor countries. By 2020, there will be over 1 billion people over 60, and 2 billion by 2050. And most of them will be in the developing world, where the numbers of the elderly will rise rapidly from 171 million in 1998 to 1,594 million in 2050.

Mrs Bani was a dancer and loves bright colours, so she refused to wear the drab colours prescribed for the 'invisible' widow in India. But although people are living longer, new problems arise, because of the breakdown of traditional extended families, which used to care for the elderly. Mrs Bani says the elderly need homes where they can live with dignity. She thinks the state should provide them.

In a neighbouring village in Bengal, 79-year-old Azirul Islam says: "Today families living collectively are finished." He attributes this to rapid population growth, which has led to as many as 150 members in a family. The result - a shortage of land and jobs, and people live under great stress. "It makes them self-centred. Today the refrain is always, 'Me and mine'."

Further East, in Japan, the dilemma is that people are living longer than anywhere else in the world. At the same time young women are choosing to have fewer babies, so the proportion of the elderly, dependant population is increasing all the time. It also means there are more sick, bedridden and senile old people. Setsuko is 77 and chooses to remain independent from her children, living alone in Tokyo and pursuing her hobby of writing. She points out that because of longevity, children are often middle-aged by the time they start looking after their parents. "This means parents disrupt their children's lives," she says. "In some cases, they destroy them completely,"

Toshiko looks after an elderly parent, but she lives with her 84-year-old mother in a 'Senior House' apartment where friends or family members can stay with the elderly. Toshiko says this arrangement allows her to carry on living her own life - otherwise she would have had to become a full-time carer: "I would have collapsed," she says.

With medical advances, more people today are living to very old ages. Kuniko is 65, but her mother is still alive at 99 and has to be looked after. She's dependent on a group of volunteers who provide informal, cheap home help for those unable to afford professional care, supported by local government subsidies. Without them, she couldn't cope.

In Japan, as in India, the traditional extended family has broken down, and more and more people are living alone. There are demographic changes too. Japanese women today have fewer than two children, compared with four or five before the Second World War. The danger is that, as the new century progresses, there won't be enough young people to look after the elderly.

In Tunisia, too, people are living longer and the numbers of elderly are on the increase. But here the traditional extended family remains strong, and today's generation continues to look after its parents. Of the 800,000 elderly in Tunisia, only one in a 1,000 lives in a home. The President has made it obligatory for working people to look after their parents - but most don't need persuading. Fouzia lives with her husband's mother, brother and sister, as well as all their children, while her husband works in France to support them all. Fouzia is proud that Arabs care for elderly people - unlike the French, she says, who care more for their pets than their elderly.

But many worry about the erosion of these values by western media and lifestyles, like Moncef Achour, the director of the only old people's home in Tunis: "It's a radical problem for society - and so for the care of old people."

TRANSCRIPT Read the full transcript of The Silver Age