Inequality gap in life expectancy and healthy life expectancy at birth (Slope Index of Inequality) in years by Local Health Board and Local Authority
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Metadata
General description
Table displays data for the National indicator "Healthy life expectancy at birth including the gap between the least and most deprived" as required by the Well-being of Future Generations (Wales) Act 2015.Life expectancy (LE) is a widely used statistical measure of the average expected years of life for a newborn based on recently-observed mortality rates. As such, LE at birth is also a measure of mortality across all ages. It should be noted, however, that mortality rates are likely to change in the future, and therefore whilst LE figures are our “best guess” at this point in time, they cannot provide a precise estimate of the lifespan of an individual.
In addition to general LE, it is important to consider healthy life expectancy (HLE). This represents the number of years a person might expect to live in good or very good health. HLE incorporates survey data on health in Wales and hence its estimation may be affected by any survey sampling error.
Life expectancy estimates are directly comparable between areas, time periods and sexes. 95 per cent confidence intervals have been produced which describe the degree of uncertainty around the estimates. These intervals can be used to ascertain the statistical significance of a difference between two estimates. If, for example, the confidence intervals between the life expectancy estimate in the earlier period and the estimate in the later period overlap, then the difference between the two is not statistically significant.
The HLE estimates are very sensitive to variation in health status data, particularly in the older age groups, where there are fewer survey responses. Welsh Health Survey data is self-reported and subject to the individual’s own perception of health.
Data collection and calculation
Life expectancy was calculated using the preferred method of the Office for National Statistics for calculating life expectancy at birth for small areas, as described by Eayres & Williams and Toson & Baker.This method has been shown to be sufficiently reliable for populations larger than 5000.
It utilises population estimates and mortality data to calculate a life table, from which the probability of surviving each 5-year age group, given that the previous age group has been survived, is calculated. It estimates the average number of years of life expected for any particular age. In this report only the average number of years of life expected from birth is presented.
The results are reported with 95 per cent confidence intervals.
The main measure of the inequality gap in life expectancy used in this report is the Slope Index of Inequality (SII). The SII is a measure of the difference in life expectancy between the most and least deprived, whilst taking into account the distribution across the whole population. As such, it is a measure that takes account of the social gradient, but summarises this as an absolute gap between life expectancy at the two extremes of the deprivation spectrum.
To measure the inequality gap in mortality rates, this report uses the rate ratio. This is calculated by dividing the rate in the most deprived fifth by the rate in the least deprived fifth. If this rate is greater than one, then the rate is higher in the most deprived fifth. A rate ratio of two means that the rate is twice as high in the most deprived fifth as in the least deprived fifth.
A particular caveat to be aware of concerns the use of population estimates supplied by the Office for National Statistics (ONS). During the preparation of this report, it was discovered that the population aged 85+ has been underestimated in some areas by the ONS estimates. In most parts of Wales, the impact of this issue on life expectancy and mortality rates will be small, and the effect on national figures is likely to be negligible. Further details are available from the webpage linked above.
