Understanding DALYs (disability-adjusted life years)

Estimating the burden of disease in one Swiss canton: what do disability adjusted life years (DALY) tell us?

BACKGROUND

Examining life expectancy and general mortality rates, the health of the population of Geneva can be described as one of the best in the world. However, in some areas Geneva fares worse than the rest of Switzerland or Europe. To re-appraise the current health priorities of the Genevan population, we analysed the relative importance of specific diseases and injuries calculating DALYs.

METHODS

We followed the procedures developed for the Global Burden of Disease (GBD) study to ensure comparability. Some adaptations were made for mortality coding. Disability was estimated based on data for countries classified as Established Market Economies (EME) in the GBD study.

RESULTS

Non-communicable diseases accounted for 79% of the disability adjusted life years (DALY), injuries represented 12%, and communicable diseases and other disorders 9%. Ischaemic heart disease was the largest single contributor to DALY, followed by unipolar major depression. Neuropsychiatric disorders and mental health accounted for more than 23% of DALY.

CONCLUSIONS

Some of the most important problems identified-depression, osteoarthritis and alcohol abuse-would have been overlooked in an analysis based solely on mortality data. The most striking finding is the importance of mental health problems. The main limitation is the lack of morbidity data for Geneva.

The social value of health programmes: is age a relevant factor?

In cost-effectiveness analysis (CEA) it is usually assumed that a quality-adjusted life-year (QALY) is of equal value to everybody, irrespective of the patient's age. However, it is possible that society assigns different social values to a QALY, according to who gets it. In this paper, we discuss the possibility of weighting health benefits for age in CEA. We also examine the possibility that age-related preferences depend on the size of the health gain. An experiment was performed to test these hypotheses. The assessment of results suggests that the patient's age is a relevant factor when assessing health gains.

Discounted lives? Weighing disability when measuring health and ruling on "compassionate" murder

This paper examines the politics of "suffering" by considering the Disability-Adjusted Life Year (DALY) alongside a controversial Canadian murder case, involving the killing of a child with disabilities by her father. The DALY aims to measure health and death correctly so as to allocate resources fairly, and eventually achieve better living conditions among the world's people. The Latimer controversy centres on the contention that some lives are not worth living, which the DALY's formula also implies. By ranking types of people according to their degree of disability, the DALY rates the lives of some people as worse than "a state equivalent to death". By examining the politics of "suffering" in the DALY and the Latimer affair, this paper underlines a valorisation of the "normal" body in much of the social science literature on health, medicine and suffering.

Discrete time representation of the formula for calculating DALYs

The global burden of disease (GBD) was measured using a new indicator called disability-adjusted life years (DALYs). The formula to calculate DALYs is based on the idea of time being a continuous variable, which is not consistent with the way economic and health data are collected and reported, and is also different from the concept of time used in the vast majority of policy analyses. Use of this formula gives rise to a time-aggregation bias in the estimates of GBD. Based on discrete time representation and the key principles outlined in the GBD study, a new formula for estimating DALYs is derived in this paper. The properties of the two formulae are compared and contrasted and the implications of using the new formula are discussed. The results show that there is an appreciable difference in percentage terms (14.06%) between the burden of cataract in Sub-Saharan Africa in 1990 calculated using the new and the old formulae. The global burden of diseases and injuries as previously reported in the GDB study may, therefore, be underestimated and the relative positions of some diseases and injuries, and hence the relative priorities of related interventions, may shift if the more appropriate, discrete-time formula is used. The difference is greatest for diseases of short duration (e.g. infectious diseases).

Setting health priorities in a Swiss canton: what do different methods tell us?

STUDY OBJECTIVE

Despite excellent mortality indicators, there is clear evidence that the health status of the population of Geneva could be improved if more attention and resources were devoted to prevention strategies. To identify a set of robust health priorities an original approach was used triangulating results between three methods.

METHODS

The study calculated potential years of life lost, disability adjusted years of life lost, and conducted a Delphi survey to gather the opinion of health professionals and the general public.

MAIN RESULTS

Several health conditions were unanimously selected by all three methods as top priorities: cardiovascular diseases, AIDS, respiratory cancer, breast cancer for women, suicide and traffic accidents. In addition, two determinants-alcohol abuse and tobacco abuse-for which a clear conceptual link could be established between all methods were chosen. Connections between priorities identified through the DALY and the Delphi method lead to further inclusion of chronic back pain and depression. Some issues solely identified through the Delphi survey were included as they were consistently considered important by professionals and the lay public alike-violence in the family, unemployment, social exclusion.

CONCLUSIONS

These results indicate that health priorities, and by extension health care priorities, would benefit from using a mix of quantitative and qualitative research methods. The triangulation of results allows for a broader perspective and makes results more acceptable.

Estimating the "avoidable" burden of disease by Disability Adjusted Life Years (DALYs)

The World Bank's Global Burden of Disease Study pioneered the use of Disability Adjusted Life Years (DALYs). In this paper we distinguish between the total and the "avoidable" burden of disease. We identify different ways of measuring DALYs: incidence-based DALYs are appropriate where the means of reducing the burden of disease is by prevention; prevalence-based DALYs are appropriate when a disease cannot be prevented but effective treatment is available. The methods of estimating each are explained and we describe how we have applied these methods to seven causes of death and disability in the South and West Region. We discuss the relevance of this work for monitoring the health of populations and deciding how best to use scarce resources to improve health.

Quality-adjusted life-years and other health indices: a comparative analysis

This article provides a descriptive overview of both unadjusted and adjusted health indices that are being applied in the current health-services research literature. We describe, give examples, and discuss a variety of the better-known health indices. Summary tables that compare health indices across dimensions, such as level of analysis, weighting methodology, preference measurement, and longevity measurement, are also included. Our goal is to provide information about similarities among and differences between health indices and enhance understanding of comparative health-outcome measurement. An extensive list of references is included to guide the reader toward additional discussions of metrics and methodologies. Given the multitude of health indices reported in the literature, this descriptive and comparative overview provides a framework for understanding these metrics in the context of health-outcomes research.

Global mortality, disability, and the contribution of risk factors: Global Burden of Disease Study

BACKGROUND

Prevention and control of disease and injury require information about the leading medical causes of illness and exposures or risk factors. The assessment of the public-health importance of these has been hampered by the lack of common methods to investigate the overall, worldwide burden. The Global Burden of Disease Study (GBD) provides a standardised approach to epidemiological assessment and uses a standard unit, the disability-adjusted life year (DALY), to aid comparisons.

METHODS

DALYs for each age-sex group in each GBD region for 107 disorders were calculated, based on the estimates of mortality by cause, incidence, average age of onset, duration, and disability severity. Estimates of the burden and prevalence of exposure in different regions of disorders attributable to malnutrition, poor water supply, sanitation and personal and domestic hygiene, unsafe sex, tobacco use, alcohol, occupation, hypertension, physical inactivity, use of illicit drugs, and air pollution were developed.

FINDINGS

Developed regions account for 11.6% of the worldwide burden from all causes of death and disability, and account for 90.2% of health expenditure worldwide. Communicable, maternal, perinatal, and nutritional disorders explain 43.9%; non-communicable causes 40.9%; injuries 15.1%; malignant neoplasms 5.1%; neuropsychiatric conditions 10.5%; and cardiovascular conditions 9.7% of DALYs worldwide. The ten leading specific causes of global DALYs are, in descending order, lower respiratory infections, diarrhoeal diseases, perinatal disorders, unipolar major depression, ischaemic heart disease, cerebrovascular disease, tuberculosis, measles, road-traffic accidents, and congenital anomalies. 15.9% of DALYs worldwide are attributable to childhood malnutrition and 6.8% to poor water, and sanitation and personal and domestic hygiene.

INTERPRETATION

The three leading contributors to the burden of disease are communicable and perinatal disorders affecting children. The substantial burdens of neuropsychiatric disorders and injuries are under-recognised. The epidemiological transition in terms of DALYs has progressed substantially in China, Latin America and the Caribbean, other Asia and islands, and the middle eastern crescent. If the burdens of disability and death are taken into account, our list differs substantially from other lists of the leading causes of death. DALYs provide a common metric to aid meaningful comparison of the burden of risk factors, diseases, and injuries.