Introduction

Across the world, population structures are changing, with particularly rapid growth in the numbers of very old people. For example, in the USA, the number of people aged 85 or over is now around 4.6 million, having grown at nearly 4% per annum since 1980.1 It appears that human longevity has been increasing gradually over many years, with centenarians only appearing as a relatively recent phenomenon about 1800,2 the age of 110 being reached in the mid-20th century and 115 only by 1990. There is no sign of this extension of longevity slowing down towards a presumed biological maximum. In addition to the increase in the maximum age, there is a decrease in mortality rates in almost all age groups, and there has been a considerable rise in the chances of surviving from age 60 to 80 over the last century, which will further increase the numbers of very old people. Furthermore, the death rate in England and Wales for people aged 85 or over has decreased throughout the twentieth century.3