Elsevier

The Lancet

Volume 386, Issue 10009, 28 November–4 December 2015, Pages 2145-2191
The Lancet

Articles
Global, regional, and national disability-adjusted life years (DALYs) for 306 diseases and injuries and healthy life expectancy (HALE) for 188 countries, 1990–2013: quantifying the epidemiological transition

https://doi.org/10.1016/S0140-6736(15)61340-XGet rights and content

Summary

Background

The Global Burden of Disease Study 2013 (GBD 2013) aims to bring together all available epidemiological data using a coherent measurement framework, standardised estimation methods, and transparent data sources to enable comparisons of health loss over time and across causes, age–sex groups, and countries. The GBD can be used to generate summary measures such as disability-adjusted life-years (DALYs) and healthy life expectancy (HALE) that make possible comparative assessments of broad epidemiological patterns across countries and time. These summary measures can also be used to quantify the component of variation in epidemiology that is related to sociodemographic development.

Methods

We used the published GBD 2013 data for age-specific mortality, years of life lost due to premature mortality (YLLs), and years lived with disability (YLDs) to calculate DALYs and HALE for 1990, 1995, 2000, 2005, 2010, and 2013 for 188 countries. We calculated HALE using the Sullivan method; 95% uncertainty intervals (UIs) represent uncertainty in age-specific death rates and YLDs per person for each country, age, sex, and year. We estimated DALYs for 306 causes for each country as the sum of YLLs and YLDs; 95% UIs represent uncertainty in YLL and YLD rates. We quantified patterns of the epidemiological transition with a composite indicator of sociodemographic status, which we constructed from income per person, average years of schooling after age 15 years, and the total fertility rate and mean age of the population. We applied hierarchical regression to DALY rates by cause across countries to decompose variance related to the sociodemographic status variable, country, and time.

Findings

Worldwide, from 1990 to 2013, life expectancy at birth rose by 6·2 years (95% UI 5·6–6·6), from 65·3 years (65·0–65·6) in 1990 to 71·5 years (71·0–71·9) in 2013, HALE at birth rose by 5·4 years (4·9–5·8), from 56·9 years (54·5–59·1) to 62·3 years (59·7–64·8), total DALYs fell by 3·6% (0·3–7·4), and age-standardised DALY rates per 100 000 people fell by 26·7% (24·6–29·1). For communicable, maternal, neonatal, and nutritional disorders, global DALY numbers, crude rates, and age-standardised rates have all declined between 1990 and 2013, whereas for non–communicable diseases, global DALYs have been increasing, DALY rates have remained nearly constant, and age-standardised DALY rates declined during the same period. From 2005 to 2013, the number of DALYs increased for most specific non-communicable diseases, including cardiovascular diseases and neoplasms, in addition to dengue, food-borne trematodes, and leishmaniasis; DALYs decreased for nearly all other causes. By 2013, the five leading causes of DALYs were ischaemic heart disease, lower respiratory infections, cerebrovascular disease, low back and neck pain, and road injuries. Sociodemographic status explained more than 50% of the variance between countries and over time for diarrhoea, lower respiratory infections, and other common infectious diseases; maternal disorders; neonatal disorders; nutritional deficiencies; other communicable, maternal, neonatal, and nutritional diseases; musculoskeletal disorders; and other non-communicable diseases. However, sociodemographic status explained less than 10% of the variance in DALY rates for cardiovascular diseases; chronic respiratory diseases; cirrhosis; diabetes, urogenital, blood, and endocrine diseases; unintentional injuries; and self-harm and interpersonal violence. Predictably, increased sociodemographic status was associated with a shift in burden from YLLs to YLDs, driven by declines in YLLs and increases in YLDs from musculoskeletal disorders, neurological disorders, and mental and substance use disorders. In most country-specific estimates, the increase in life expectancy was greater than that in HALE. Leading causes of DALYs are highly variable across countries.

Interpretation

Global health is improving. Population growth and ageing have driven up numbers of DALYs, but crude rates have remained relatively constant, showing that progress in health does not mean fewer demands on health systems. The notion of an epidemiological transition—in which increasing sociodemographic status brings structured change in disease burden—is useful, but there is tremendous variation in burden of disease that is not associated with sociodemographic status. This further underscores the need for country-specific assessments of DALYs and HALE to appropriately inform health policy decisions and attendant actions.

Funding

Bill & Melinda Gates Foundation.

Introduction

The Global Burden of Disease study 2013 (GBD 2013) seeks to bring together all available epidemiological data using a coherent measurement framework, standardised estimation methods, and transparent data sources to allow comparisons of health loss to be made over time and across causes, age–sex groups, and geographies. The GBD 2013 data for disease and injury incidence and prevalence, years lived with disability (YLDs), causes of death, and years of life lost because of premature mortality (YLLs) for 188 countries provide an opportunity to assess the effect of recent changes in population health by examining summary measures of health loss attributed to specific causes, expressed in DALYs, and summary measures of average population health, expressed as HALE.1, 2 These measures are crucial to track health progress, strengthen policy decisions, assess programme effects and results, and inform health service and research priorities. Such holistic measures of population health, encompassing both disability and mortality levels and patterns in populations, are also attracting interest as part of the discussion around the Sustainable Development Goals .3, 4, 5

A hallmark of the GBD approach is an emphasis on making national data easier to compare by taking into account the extensive variation that exists in national medical certification and cause of death coding practices and widely varying case definitions and measurement methods used to track the incidence and prevalence of diseases and injuries.1, 2 The GBD not only provides detailed metrics for specific causes, but also generates summary measures, such as DALYs and HALE, which enable comparative assessments of broad epidemiological patterns across countries and different time periods. HALE is a useful summary of overall health for a country and DALYs allow assessment of both premature mortality and non-fatal outcomes by cause. These broad summary measures allow quantification of general trends, such as the epidemiological transition, while also making clear how countries and regions deviate from general patterns.6, 7, 8, 9 The unfolding of the HIV epidemic and the rise of adult mortality, especially among men in Eastern Europe and Central Asia, have called into question the notion of a universal pattern of epidemiological change that occurs with sociodemographic development.2, 10, 11, 12, 13 However, the general notion of a shift from communicable to non-communicable causes of disease burden and injuries remains a powerful framework for global and regional health policy debates.9, 14, 15, 16, 17, 18 The GBD provides an opportunity to quantify these patterns and explore the extent to which epidemiological change is driven by sociodemographic change, reduction of health risks, improvement of health management, or other local factors.

GBD 2013 results for deaths, YLLs, incidence, prevalence, and YLDs by cause for 1990 to 2013 for 188 countries have already been published.1, 2 In this study we use these GBD 2013 results to calculate DALYs and HALE. These summary metrics are used to characterise broad patterns of lost healthy life and cross-country variations within these patterns. The GBD 2013 provides a complete re-analysis of each country's data from 1990 to 2013 and thus supersedes all previously published GBD analyses of DALYs and HALE.

Section snippets

Study design

GBD 2013 uses a hierarchy of causes that organises 306 diseases and injuries into four levels of classification, the rationale for which has been described previously.2, 19 The first level distinguishes three broad categories: first, communicable, maternal, neonatal, and nutritional disorders; second, non-communicable diseases; and third, injuries. Level 2 has 21 mutually exclusive and collectively exhaustive categories, level 3 has 163 categories, and level 4 has 254 categories. The full cause

Global

Global life expectancy at birth for both sexes combined increased from 65·3 years (95% UI 65·0–65·6) in 1990 to 71·5 years (71·0–71·9) in 2013, whereas during the same interval, HALE at birth for both sexes combined increased from 56·9 years (54·5–59·1) to 62·3 years (59·7–64·8). The survivorship curves shift up and to the right with increasing quintiles of country sociodemographic status (figure 1). In the three groups of countries, defined as the lowest, middle three, and highest quintiles of

Discussion

Global health is improving: life expectancy at birth rose by 6·2 years between 1990 and 2013, while HALE at birth increased by 5·4 years during the same interval; worldwide, age-standardised DALY rates fell by 27%. Global progress has accelerated since 2005 because of major reductions in HIV/AIDS and malaria, in addition to continued progress against other major communicable, maternal, neonatal, and nutritional disorders. Although the total volume of DALYs is down by only 3·6% over the 23 year

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