Healthy life expectancy (HALE) is the average number of years a person is expected to live in good health at a certain age (e.g. at birth or 60 years), given the conditions of mortality and morbidity prevailing in the population. It measures both the length and quality of life, complementing the more widely used indicator life expectancy, which only measures the length.

HALE may also be called healthy life years (HLY), disability-free life expectancy (DFLE), or disability-free life years (DFLY). In some cases, these names are used interchangeably with the same underlying estimation method, while in other cases HALE is used to describe estimates based on different methods. Caution should be taken when comparing estimates from various sources.

The differences between WHO and country estimates of HALE, as well as estimates from other institutions, mainly come from 1) the data inputs and 2) the estimation methods. These two elements are often interdependent, as the form of data inputs is determined by the methods to be applied, and the availability of data may limit the options of estimation methods.

For HALE estimation within the GPW13 Results Framework, WHO proposes the Sullivan method, which is also applied in WHO’s regular updates of HALE for the Global Health Estimates (GHE).

This method apportions the remaining life expectancy at a certain age into years lived in full health and years lived in less than full health. The estimation requires two types of data inputs: 1) mortality: average number of years lived in each age group from life tables; 2) morbidity: prevalence of disability in a population.

Alternative measures for disability prevalence, unweighted or weighted using different schemes, are available from other analyses using various types of data and instruments for defining healthiness and disability. Below are some measures for disability in population-based surveys that are commonly used in Member States:

1) The “Self-reported health” approach that asks respondents to rate their levels of health. (e.g. excellent, very good, good, or poor)

2) The “Limitation of activities” approach, including Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL), that collects information on individuals’ performance of essential activities for an independent life (e.g. for ADL: bathing, dressing, eating, toileting; for IADL: preparing own meals, shopping for personal items, managing money, and managing medication).

3) The “Global Activity Limitation Index (GALI)” approach which asks the degree to which an individual has been limited due to health issues in normal activities for duration of six months or more (e.g. not limited, limited but not severely, or severely limited).

Because of variation in survey design, question wording, frequency of surveys, healthcare system, as well as social and cultural factors, estimates of population-level morbidity from one country may not be readily comparable with other countries or global estimates, or from one year to another. It is therefore critical to use globally comparable methods and estimates for reporting HALE in the GPW13 Results Framework.

Besides the proposed Sullivan method, another method is the “Multistate life table” approach that 1) models the transition rates between different health states including death; 2) allows two-way transitions between all non-fatal health states; and 3) allows death rates to vary by health states. This method is more flexible yet more computationally complex and requires longitudinal data as an input.

HALE is intended to serve as an overarching integrative indicator for reporting the overall progress towards the combined GPW13 Triple Billion targets. All health gains achieved through meeting the Triple Billion targets will ultimately be reflected in gains of HALE.

However, attributing the gain in HALE to each of the Billion Targets or their underlying indicators is not possible at present, primarily for two reasons:

1) The estimation requires a two-stage method: i) decomposing the change in HALE over time to those due to change in mortality and those due to change in morbidity, ii) attributing the changes in mortality and morbidity, respectively, to each of the three Billions, indicators or risk factors. A comprehensive analysis of comparative risk assessment to quantify the independent impact of Billions or indicators on mortality and morbidity is needed to enable the second-stage analysis. This is data-demanding and computationally intensive, and typically challenging for individual countries to perform such analysis routinely.

2) The Triple Billion targets are interrelated to some extent, impacting the same set of health outcomes directly or indirectly, and resulting in some overlaps. For example, cardiovascular disease is addressed in the UHC (Universal Health Coverage) Billion directly through hypertension treatment, and also in the Healthier Populations Billion indirectly through tobacco control, reducing harmful alcohol use, improve air quality, etc. Additionally, indicators like access to well-managed sanitation are included in the Healthier Population Billion and also in the UHC billion (albeit used as a proxy for service coverage). Overlaps between the Billions and among the relevant indicators render the assessment of individual and independent impact of each Billion and indicators challenging.

Given these challenges, assessing the contribution of each Billion or underlying indictors to the gain in HALE would require further development of methods as well as additional data and analyses. Also, attributing the estimated overall HALE values to progress in a subset of the Billions or indicators, as opposed to using it as an overarching measure for all, would be misleading. It would overestimate the contribution of the included indicators while not accounting for other relevant factors or indicators to health outside the current framework.

HALE is one of the most comprehensive measures, addressing both mortality and morbidity, and summarizing the overall burden of diseases and injuries.

It is expressed in number of years, which is interpretable for policy dialogues, and resonates with the general public as a measure of the average number of years a person can expect to live in good health.

The estimation method is also straightforward and can be easily implemented by countries, provided required data inputs are available.

Other indictors tend to lack this comprehensiveness and/or comparability. In the case of avoidable deaths, it only addresses mortality, while the average number of years people live in disability is increasing as life expectancy extends. And it only focuses on the deaths that are avoidable rather than the overall disease burden. The definition of avoidable deaths may vary across different countries, depending on individual country’s population health priorities and capacity in successfully avoid deaths through prevention and treatment for what causes in what demographic groups.

More precise assessment of avoidable deaths and the interventions to reduce them would require more data with varying forms and from different sources, and more complex methodology. Most elements of the required data input would need to come from population-based epidemiological studies rather than from routine data collection mechanisms. Regular updates of the data and corresponding analyses are essential in the GPW13 Results Framework, yet in practice few countries currently have the resources or capacity to calculate avoidable deaths on their own.