Until eight months ago, Freda Gibson drove regularly around London and was behind the wheel when she returned from Wales after an annual walking trip. 

She lives alone, shops and cooks for herself. But after more than 70 years she decided to give up driving and prefers to stay close to the home she has lived in for more than half a century. 

At six months shy of her 94th birthday who could blame her? Her eyesight is failing and she has the odd memory lapse, but apart from that, Gibson says she feels fine. 

"My doctor says there's no reason I shouldn't see 100," she says with a sly smile. 

If she reaches 100, she won't be alone. The number of centenarians in England and Wales has doubled about every 10 years and is expected to hit 39,000 by 2036. 

Lower birth rates, longer life expectancy and retiring baby boomers mean that in the next four years the number of 55 to 64-year-olds in Europe will exceed those in the 15 to 24-year age group. 

"Experts predict that the world will have 2 billion people over 60 by 2050, up from the current 600 million. Ageing societies are a reality," Ursula Haubner, the Austrian minister of generations and social affairs, told a meeting on health and ageing in Vienna. 

LIVING HEALTHIER LONGER 

Some experts believe medical advances could push age boundaries beyond the current upper limit of 120 and the average life expectancy in developed countries from about 80 to more than 100. 

Like Gibson, who has enjoyed good health throughout her long life, more elderly people are choosing to live alone. 

"In Western Europe the trend is, if you are able, to live on your own or with your spouse," said Professor Emily Grundy, a demographic gerontologist at the Centre for Population Studies at the London School of Hygiene and Tropical Medicine. 

Couples and single people sometimes decide to move to another area or country after they retire. Usually, it is only a small proportion of retirees but Grundy said it has a big effect because they tend to go to the same places. 

Coastal towns in Britain, villages in southern Spain and France, and cities in Florida and Arizona in the United States are favourite destinations. 

"Only in the face of serious disability towards the end of life does moving, either to an institution or with relatives, become more common," Grundy added. 

Medical experts predict one of the biggest challenges of an ageing population -- alongside a greying workforce, supporting pensions, age discrimination and equitable access to health care -- will be learning how to live healthier longer. 

As the world ages, cases of Alzheimer's disease, the leading cause of dementia in the elderly, are predicted to double every 20 years and could reach more than 81 million by 2040. 

The progressive, degenerative disorder, which attacks the brain's nerve cells resulting in loss of memory and mental ability, affects an estimated 12 million people worldwide. 

"Alzheimer's is the absolutely crucial thing," said Grundy. 

"At the moment there is not much sign of a really effective preventive treatment. It is very strongly age-related and it needs quite extensive long-term care for four or five years." 

Parkinson's disease, cancer, heart disease, stroke, osteoarthritis, the eye disorder macular degeneration and depression are other illnesses that afflict the elderly. 

Professor Claude Le Pen, a health economist at the Universite Paris Dauphine in France, estimates that on average in the European Union about 15 percent of the ageing population who are in very poor health will lead to around 60 percent of health-care expenses. 

He believes any investment in improving peoples' interest in health and ageing will benefit both the individual and society. 

AGEIST ATTITUDES 

Keeping elderly people active physically and mentally as well as socially connected to family and friends is crucial for maintaining health. Part of the problem is that societies are not ageing as individuals do. The emphasis on youth can have a negative impact on the elderly, according to the experts. 

"We need to be more creative and imaginative about the kinds of contributions which older people might make in their communities, in neighbourhood organisations and by volunteering," said Robert Anderson, of the Dublin-based European Foundation for the Improvement of Living and Working Conditions. 

Le Pen believes governments should do more to keep older people at work by tackling age discrimination in recruitment. Grundy agrees. 

"Governments have to be able to work across parties to come up with long-term consensus plans. In terms of health care, we need to focus on doing something about Alzheimer's and musculoskeletal problems which cause a lot of disability that inhibits people from looking after themselves," she said. 

"We need to become less ageist. Manufacturers are already looking at the older person's market." 

If politicians ignore the concerns of the elderly it will be at their peril because, as Grundy noted, they are an important part of the electorate, almost the majority in some places and they are more likely to vote than younger people. 

"We need to make the most of elderly people and change our institutions to deal with this. It is going to affect every area of life," Grundy added. 

Gibson says the best thing about being in her 90s is still being able to do things she enjoys -- daily walks, gardening and listening to classical music. 

"Sometimes lately I've thought I'm ready anytime now but then I think perhaps I'll have few more years."