Measuring Disease Burden

Measures of disease burden commonly used in epidemiological research are considered elsewhere in these notes, along with population attributable risks and the challenge of choosing suitable comparison groups in public health.

This page addresses the measurement of disease burden on a wider, national scale.

Disease burden

Disease burden is the impact of a health problem on a given area, and can be measured using a variety of indicators such as mortality, morbidity or financial cost. This allows the burden of disease to be compared between different areas for example regions, towns or electoral wards (see small area analysis section). It also makes it possible to predict future health care needs.

Disease burden is often measured using two widely accepted indicators, that facilitate comparison of the burden of different diseases and take into account both death and morbidity in a single measure:

• Quality-Adjusted Life-Years (QALY) take into account both quantity and the quality of life generated by healthcare interventions. It is the measure of the life expectancy corrected for loss of quality of that life caused by diseases and disabilities. Some health interventions do not prolong life but do significantly improve the quality of life. A year of normal health is given a QALY of 1 whilst a year of complete functional impairment (e.g. death) has a QALY of 0
• Disability Adjusted Life Years (DALY) are a measure of the burden of disease and reflects the potential years of life lost due to premature death (PYLL) and equivalent years of 'healthy' life lost by virtue of being in states of poor health or disability. These disabilities can be physical or mental. One DALY can be thought of as one lost year of 'healthy' life

Global Burden of Disease Study

Probably the most well known assessment of disease burden is the Global Burden of Disease (GBD) Study carried out by the World Health Organisation. GBD researchers first devised the concept of DALYs. The first study in 1990 sought to quantify the health effects of more than 100 diseases and injuries for eight regions of the world, generating estimates of mortality and morbidity by age, sex and region.¹

The GBD Study was most recently updated in 2004 and the report can be accessed here. It provides estimates of the leading causes of death in the world, and the top three causes include coronary heart disease, cerebrovascular disease, and lower respiratory tract infections.²

Why measure disease burden?

The results of the GBD make interesting reading from a public health perspective, but the WHO team also provide helpful guidance on the practicalities of measuring disease burden on a local and national scale.³ They suggest several reasons why it is important to measure disease burden:

• Prioritizing actions in health and the environment
• Planning for preventive action
• Assessing performance of healthcare systems
• Comparing action and health gain
• Identifying high-risk populations
• Planning for future needs
• Setting priorities in health research

References

1. http://www.who.int/healthinfo/global_burden_disease - Accessed 31/01/09
2. http://www.who.int/mediacentre/factsheets - Accessed 31/01/09
3. Prüss-Üstün A, et al. Introduction and methods: assessing the environmental burden of disease at national and local levels. World Health Organization, 2003. (WHO Environmental Burden of Disease Series, No. 1).

© Helen Barratt, Maria Kirwan 2009