Healthy life expectancy for 187 countries, 1990–2010: a systematic analysis for the Global Burden Disease Study 2010

Summary

Background

Healthy life expectancy (HALE) summarises mortality and non-fatal outcomes in a single measure of average population health. It has been used to compare health between countries, or to measure changes over time. These comparisons can inform policy questions that depend on how morbidity changes as mortality decreases. We characterise current HALE and changes over the past two decades in 187 countries.

Methods

Using inputs from the Global Burden of Disease Study (GBD) 2010, we assessed HALE for 1990 and 2010. We calculated HALE with life table methods, incorporating estimates of average health over each age interval. Inputs from GBD 2010 included age-specific information for mortality rates and prevalence of 1160 sequelae, and disability weights associated with 220 distinct health states relating to these sequelae. We computed estimates of average overall health for each age group, adjusting for comorbidity with a Monte Carlo simulation method to capture how multiple morbidities can combine in an individual. We incorporated these estimates in the life table by the Sullivan method to produce HALE estimates for each population defined by sex, country, and year. We estimated the contributions of changes in child mortality, adult mortality, and disability to overall change in population health between 1990 and 2010.

Findings

In 2010, global male HALE at birth was 59·0 years (uncertainty interval 57·3–60·6) and global female HALE at birth was 63·2 years (61·4–65·0). HALE increased more slowly than did life expectancy over the past 20 years, with each 1-year increase in life expectancy at birth associated with a 10-month increase in HALE. Across countries in 2010, male HALE at birth ranged from 27·8 years (17·2–36·5) in Haiti, to 70·6 years (68·6–72·2) in Japan. Female HALE at birth ranged from 37·1 years (26·8–43·8) in Haiti, to 75·5 years (73·3–77·3) in Japan. Between 1990 and 2010, male HALE increased by 5 years or more in 48 countries compared with 43 countries for female HALE, while male HALE decreased in 22 countries and 11 for female HALE. Between countries and over time, life expectancy was strongly and positively related to number of years lost to disability. This relation was consistent between sexes, in cross-sectional and longitudinal analysis, and when assessed at birth, or at age 50 years. Changes in disability had small effects on changes in HALE compared with changes in mortality.

Interpretation

HALE differs substantially between countries. As life expectancy has increased, the number of healthy years lost to disability has also increased in most countries, consistent with the expansion of morbidity hypothesis, which has implications for health planning and health-care expenditure. Compared with substantial progress in reduction of mortality over the past two decades, relatively little progress has been made in reduction of the overall effect of non-fatal disease and injury on population health. HALE is an attractive indicator for monitoring health post-2015.

Funding

The Bill & Melinda Gates Foundation

Introduction

Improvement of population health means more than simply delaying death or increasing life expectancy at birth. People and societies are also concerned about the presence of disease and about degrees of functioning. Over the past six decades, advances in medicine and public health, improved living standards, greater educational attainment, and decreased fertility have contributed to huge reductions in mortality in most world regions.1, 2, 3 With the accompanying trend of population ageing, the need to prioritise healthy ageing is increasingly recognised.4, 5 Design and implementation of effective interventions and programmes, organisation and financing of health systems, and monitoring of progress toward goals for health and development all need valid and comparable measures of the population's health, including mortality and non-fatal outcomes.

More than 40 years ago, Daniel Sullivan developed a method to account for both mortality and morbidity in a single index capturing the expected years of survival free of disability,⁶ building on earlier work.⁷ Such single measures of overall population health provide a useful adjunct to measures of health gaps, such as disability-adjusted life-years, which are often disaggregated by disease and injury.⁸ Healthy life expectancy is a summary measure of population health that has evolved from Sullivan's concept.9, 10, 11 Healthy life expectancy is the number of years that a person at a given age can expect to live in good health taking into account age-specific mortality, morbidity, and functional health status.

Healthy life expectancy is part of a class of population health measures called health expectancies,¹² which all combine mortality and morbidity information in a single index, but differ in how non-fatal outcomes are defined, categorised, and evaluated. Health expectancies have been computed for several countries and regions over time (eg, Austria, South Australia, China, Denmark, Hong Kong, India, the UK, and the USA).13, 14, 15, 16, 17, 18, 19, 20 Since 2004, the European Union has used a health expectancy measure—healthy life-years—as one of its structural indicators for yearly monitoring of outcomes related to health-care and retirement policies.21, 22 Health expectancies have also been calculated for some subnational populations (eg, municipalities in Japan, health-care regions in the Netherlands, and several states in the USA),23, 24, 25, 26 and even for a large general practice in the UK.²⁷ Several studies have focused on differences in health expectancies in relation to sex or socioeconomic status.28, 29, 30, 31, 32, 33 The Global Burden of Disease project calculated healthy life expectancy for 191 countries between 1999 and 2002.10, 34, 35, 36, 37, 38, 39

Health expectancies are appealing, simple, summary measures of population health. However, many alternative approaches to estimation of health expectancies have been proposed.¹² These approaches sometimes differ in how they combine information about mortality and morbidity in the life table. Sullivan's original approach—still the most common method—was to combine mortality from a period life table with cross-sectional information for prevalence of morbidity. Researchers have compared Sullivan's approach with alternatives—for example, based on multistate life tables—and established the statistical properties of Sullivan's method.⁴⁰

Approaches to calculation of health expectancies also differ with respect to three factors related to definition and measurement of non-fatal outcomes. First, a range of health outcomes and constructs have been used, with some applications focusing on the absence of disability expressed as activity restriction,41, 42 some on avoidance of major diseases such as dementia,43, 44 and others on a broader multidimensional construct of functioning.10, 45 Second, the empirical basis for estimation of the prevalence of reduced health has varied. Some studies rely on self-reported data from surveys,13, 28, 46 whereas others use extensive combinations of self-reported, measured, and functional test data.¹⁰ Third, studies have used different methods to weight outcomes to assign the contributions of years lived in different health states to overall healthy life expectancy. Some measures use dichotomous schemes, whereby thresholds are defined for major morbidity and disability.9, 22 In these schemes, morbidity or disability that exceeds the threshold makes no contribution to healthy life expectancy, whereas any morbidity or disability below the threshold contributes a full year. Other measures use detailed categorisation of outcomes and an associated weighting scheme, by which a set of health states are assigned weights on a scale from 0 to 1, where 0 is equivalent to death and 1 is equivalent to ideal health.10, 45 Choices about definition and measurement of health outcomes have important implications for the interpretation of health expectancy results, particularly for comparisons between settings or over time.

The extent to which trends in prevalence of health conditions accord with or diverge from trends in mortality is crucial for understanding the development of human health and the performance of health systems.⁴⁷ In some settings in the 19th and 20th centuries, as mortality decreased, morbidity increased substantially.48, 49, 50, 51 Gruenberg⁵² and Kramer⁵³ argued that because of medical intervention, disease case-fatality rates fell but incidence did not, leading to higher disease prevalence (expansion of morbidity). Fries and others54, 55, 56, 57 have argued the opposite view, that as mortality decreases, the age of onset of chronic conditions is delayed through prevention, leading to shorter durations of conditions with functional impairment (compression of morbidity). The debate about expansion versus compression of morbidity continues, and touches on important questions about the future of public health and health-care costs.58, 59, 60 A third, intermediate scenario is a dynamic equilibrium in which severe disability decreases but mild and moderate disability increase as life expectancy increases.61, 62, 63, 64 Calculation of life expectancy, healthy life expectancy, and the difference between the two—which can be interpreted as the average number of years of healthy life lost to poor health—offers a direct and simple method to assess the relation between changes in mortality and morbidity and test competing hypotheses.

The Global Burden of Disease Study (GBD) 2010 provides estimates of the prevalence of 1160 sequelae of disease and injury based on systematic analyses of all available data for 187 countries in 1990 and 2010, along with new estimates of disability weights representing the magnitude of health losses associated with each sequela.65, 66 Because prevalence is analysed by age the results of the GBD 2010 can be used to estimate healthy life expectancy. Previous versions of the GBD have been used to estimate healthy life expectancy by region for 1990,⁶⁷ and for countries in 1999, with revisions up to 2002.10, 34, 35, 36, 37, 38, 39 In this report, for the first time, we assess healthy life expectancy at two timepoints, across 187 countries, using comparable methods, to characterise current levels and patterns as well as change over the past two decades.