Worldwide, we are currently witnessing an unprecedented demographic transformation, as life expectancy increases from the present 66 years of age to 77 years of age by 2050, and the proportion of the population over 60 doubles from 10 to 21%. A result of this increase in life expectancy is that the number of persons over the age of 60 years will rise from the current 600 million to around 1.5 billion by 2050. Britain will have over 6 million people over 75 years – double the 1985 figure, but significantly the great majority of older adults will reside in the less developed regions of the world (see also ‘Ageing and health behaviour’). Currently around 60% of the world's older population live in less developed countries, i.e. an estimated 279 million: by 2050 this proportion is projected to increased to 88%. This explosion in numbers of the over-70s will bring higher incidences of age-related illness and infirmity. Longevity is one of humanity's major achievements, but it brings with it the challenge to adjust our societies to this new reality by changing attitudes, introducing new political, social, health and economic measures that shift us from the current youthful pyramidal structures that are becoming obsolete in most world regions, though at a significantly faster rate in the more industrialized countries. Many less developed countries are currently experiencing a significant downturn in natural population increase (births minus deaths), similar to the decline that occurred in industrialized nations a few decades earlier.