Academic journal article Bulletin of the World Health Organization

Measurement and Utilization of Healthy Life Expectancy: Conceptual Issues

Academic journal article Bulletin of the World Health Organization

Measurement and Utilization of Healthy Life Expectancy: Conceptual Issues

Article excerpt

The periodic calculation of healthy life expectancies permits the evaluation of the impact of new health policies at a given moment, as well as the assessment of trends under changing health conditions. In spite of their apparent simplicity, the results obtained will have to be interpreted by experts. Useful reference values can be provided by international comparisons. However, several choices remain to be made, such as (i) the types of morbidity and disability data to be associated with mortality data; (ii) the multiple indicators available; (iii) the type of observations to be recorded, i.e., "abilities" or "performances"; (iv) whether or not the recovery of lost functions should be considered; (v) the mode of computation, i.e., life expectancy before the first morbid event or global healthy life expectancy; and (vi) the determination of thresholds based on either relative or absolute criteria.

Determining population health status

Numerous attributes have been attached to the measurement of healthy life expectancy [1]. But in the absence of a clear distinction between the health status of individuals and that of populations, two questions arise that are connected and often confused with one another:

(1) By living to a greater age, are we not individually becoming more and more weak and decrepit? (2) As more peole survive at every age level, are we not collectively becoming less strong and less effective at each increasing age?

Any calculation of healthy life expectancy must take into account the health status of the population and determine whether this improves over a period of time.

A calculation of cross-sectional healthy life expectancy answers the first question given above for a fictitious cohort of individuals who would be subject, at all ages, to various health influences during a chosen period (e.g., one year) -- influences such as forces that determine mortality, morbidity, disability, and cure or recovery. This calculation cannot measure [1] the health status of the individual because each member of the cohort would have experienced or will experience a different history, or [2] the health status of the population, which during the chosen period would involve multiple cohorts, but it can measure the conditions influencing the population's health during the given period. Repeating the cross-sectional calculation would indicate the changes in healthy life expectancy of that same fictitious cohort when subjected at each age period to specific health conditions over many years in succession. A comparison of the figures obtained for these successive cross-sectional life expectancies provides an answer to the second question.

It is well known that in Western countries the successive cross-sectional life expectancies have increased greatly during the present century. The conclusion from this is that the conditions for a longer life are evolving favourably. But what about the healthy life expectancies in the same moment and conditions, if it had been possible to calculate them? Would they also have increased and, if so, at the same rate or more quickly or less quickly than the life expectancies?

The various cases

As regards each cohort exposed to different successive sets of health conditions, (i) is there an absolute or relative "compression" in the number of years of bad health within the life expectancy [2], or (ii) has more or less of a "balance" been maintained between the numbers of years of good and bad health, or (iii) is there a general "expansion" in the number of years of bad health [3]? Unfortunately certain results show that under successive time periods the disability-free life expectancy will increase less quickly than life expectancy [1]. In such cases, which are perhaps the most probable for the immediate future, the improvement in healthy life expectancy would, paradoxically, be accompanied by an increase in the number of years lived in bad health within the total life expectancy. …

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