Healthy life expectancy: introduction
What is life expectancy (LE)?
Put at its simplest, LE is an estimate of how long the average person might be expected to live. LE is most often quoted for an entire lifetime; LE at birth is the number of years that a newborn baby would live if they experienced the death rates of the local population at the time of their birth, throughout their life. It is a theoretical measure rather than a true prediction of life expectancy, since death rates may increase or decrease during a person's lifetime, and people may move to areas with different mortality risks.
LE can also be calculated for other ages. For example, LE at age 65 indicates the number of further years that a 65-year-old might be expected to live. As a person who reaches 65 has already survived many years, their LE when added to their current age (65) will generally be greater than the corresponding estimate of a baby's LE at birth. For example, a 65-year-old man might have a LE of 15 years, meaning that he might be expected to live until the age of 80; whereas a boy's LE at birth might only be 73 years.
While LE is a very useful measure, it does not take account of how healthy someone is during their life. The measure of healthy life expectancy attempts to do this.
What is healthy life expectancy (HLE)?
Put at its simplest, HLE is an estimate of how long the average person might be expected to live in a 'healthy' state. Like LE, it is most often expressed for an entire lifetime from the time of birth. HLE at birth is the number of years that a newborn baby would live in 'healthy' health if they experienced the death rates and levels of general health of the local population at the time of their birth, throughout their life.
HLE is calculated by combining LE and a measure of 'healthy' health: in these HLE analyses for Scotland the measure used is self-assessed general health (see HLE technical paper (section 1.4). This is self-reported by survey or Census respondents but has been shown to reflect both mental and physical health.
Why is HLE useful?
HLE provides a single summary measure of a population's health, which takes account of the population's health status and death rates at different ages. HLE can be used to look at health trends over time and to compare the health of different populations and population sub-groups. It is useful in resource allocation, planning of health and other services, and evaluation of health outcomes. Further information on the uses made of HLE estimates, and users’ experiences of the statistics, are included in the HLE technical paper (Appendix B).
Why look at HLE alongside LE?
While one aim is to maximise LE for the population, a second aim is to maximise HLE for the population. In other words, the target is a healthy life and not just a long life. The gap between LE and HLE indicates the length of time likely to be spent in 'not healthy' health by the average person, and therefore when considering time trends a third aim is to try to increase HLE so that it comes closer to LE, reducing the gap or period of morbidity (ill-health). The proportion of the average lifetime expected to be spent in 'healthy' health (HLE/LE) is often used to assess whether over time there is a compression of morbidity (proportion increasing, i.e. less time spent in poor health) or an expansion of morbidity (proportion decreasing, i.e. more time spent in poor health).
The period spent in 'not healthy' health will tend to occur towards the end of life, but LE and HLE are average measures and some people experience 'not healthy' health in their early years.
Both LE and HLE are usually estimated for males and females separately, as in Western Europe women generally outlive men by several years. More detailed notes on LE and HLE and methodology can be found in the HLE technical paper.
What other measures of health expectancy are there?
The global term for HLE and other similar measures is health expectancy. While these HLE analyses for Scotland are based on self-assessed general health, alternative measures of health can be used. One of the most common is the absence of limiting long-term illness or disability (primarily a measure of physical functioning), leading to the estimation of disability-free life expectancy (DFLE) which is sometimes also called healthy life years.