The 21st century – the last century of youth?

At this year’s Oxford London Lecture, Oxford University gerontologist Professor Sarah Harper spoke about the implications of a falling birth rate coupled with rising longevity – a phenomenon affecting most countries across the globe.

At the public lecture, entitled 'The 21st century – the last century of youth?', Professor Harper, Director of the Oxford Institute of Population Ageing, pointed to UN estimates that show the proportion of children per population in most countries is likely to fall to 15% or lower by the end of this century. In some countries it could even dip to that level by 2050, she noted.

Meanwhile, life expectancy is now increasing rapidly in the more developed world, and catching up in the emerging economies thanks to improvements in public health and medical advances, she said. Demographers who have attempted to build assumptions about future scientific and medical advances into their forecasts say the number of centenarians may reach almost one million in the UK alone by the end of the century.

Professor Harper also commented on a marked increase in the use of expensive new drug therapies which have helped us to live longer, noting this trend is likely to increase. But she warned against embracing pharmaceutical advances as a replacement for public education programmes on healthy living, saying: 'I think we may be entering a world where preventable chronic disease will not be prevented by public health measures tackling lifestyles, but increasingly by drug therapies which will control and reduce symptoms of chronic disease.

'We have to ask if we wish our future to be one where individuals at increasingly younger ages pop pills rather than eat healthily, stop smoking, reduce alcohol, and take up exercise.'

Drawing on their database of nearly two million occupational pension records, researchers at the Oxford Institute of Population Ageing have found that healthy lifestyles have contributed as much to raising life expectancies as high incomes. Professor Harper said 65 year-old-men retiring in ill health who had a low income and an unhealthy lifestyle could expect to live another 11 years, but 65-year-olds with healthy lifestyles added an extra four years to their lives, regardless of income. 

On the issue of global population predictions, Professor Harper noted global fertility rates are dropping, a phenomenon identified by demographers as 'the decline of the two-child family'. She said: 'If there is one thing which demographers failed to predict last century, it is how fast the total fertility rate would fall.' 

She said that there are now warnings of a 'low fertility trap', whereby children in low-fertility countries adapt to the childless or one-child family model, thereby causing fertility rates to decline further. She cited anecdotal evidence emerging from China, where the one-child policy has been in place for 30 years. It shows that most Chinese people are choosing to have just one child themselves because of their experience in single-child families, despite the fact that they are allowed two children.

Professor Harper also talked about the rising health costs of an ageing population. She cited another study involving the Institute that showed that the main driver of health care costs in OECD countries has not been solely an ageing population but the increasing costs of health provision. These costs have been driven up particularly through advances in medical techniques and drug therapy, as well as increased general demand.

She concluded: 'The message is I think clear– the 21st century is unlikely to be the last century of where youth exists, but it is also unlikely that we will see a return to population structures dominated by young people. In that sense it will be the last century to see the youthful demographies which the human race has experienced to date. We are seeing unprecedented change in our population structures.'

The Oxford London Lecture 2012 was staged in association with The Guardian. It is an annual lecture series hosted by the Vice-Chancellor of the University of Oxford. The series aims to explore the latest Oxford research and consider how it can affect the world in the 21st century.