Actuaries and medical doctors are united in their desire to understand what influences human mortality. Mathematician Benjamin Gompertz was the first to observe in 1825 that mortality rates increase exponentially with age, in that the chance of death approximately doubles every eight years of life.
Application of Gompertz mortality curve
Age is therefore also classified as a key risk factor for predicting a person’s life expectancy. Other risk factors include gender, prior disease, access to treatments, occupational hazards and smoking.
However, when data is not readily available for certain risk factors, proxies can be found. For example, where a person lives may not be a risk factor, but it can provide proxies for risk factors such as access to healthcare.
Year of birth is a valuable proxy. It helps map exposure to different risk factors over the lifetime of a group of people, and assess the potential impact on their future longevity. For example, those born in Germany, the UK and Japan in the early 1930s not only benefitted from warnings on the dangers of smoking in the 1970s, but also from successive developments in treatment options and clinical guidance for high blood pressure and high cholesterol.
Uncertainties for how risk factors and proxies will develop pose a significant challenge when making predictions about future longevity. One estimate suggests that, today, a 65-year-old woman in the UK can expect to live another 20.9 years and a 75-year-old 13.1 years. But a number of other estimates could be put forward and reasonably supported.
It is even more difficult to assess how long a 75-year old woman might live in ten years’ time, illustrated below with just some of the medical advances that took place between 2000 and 2010.
ABC News and Med Page Today’s top-ten US medical advances of 2000 – 2010
Every generation has a unique life history of shared events and innovations. One generation might be less susceptible to disease than the next, but the later generation could live longer through medical advances or having healthier lifestyles. The complex interaction between risk factors, disease and treatment means that historical trends do not tell the whole story.
Considerations when building a forward-looking, disease-centred approach for assessing future longevity