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Measures of disease burden (event-based and time-based) and population attributable risks including identification of comparison groups appropriate to Public Health

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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. See “Numerators, denominators and populations at risk” and “Years of life lost”.

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 population, 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 “Analysis of health and disease in small areas”). 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) are a 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; QALY take into account both quantity (length) and the quality of life generated by a healthcare intervention. A year of life in perfect 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) reflect the potential years of life lost due to premature death (YLL) 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.

More information on how to calculate QALYs and DALYs is given in Section 4D, Health Economics “Economic appraisal”.
 

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 is regularly updated, with most recent estimates based on data from 2016, published in 2017. The reports can be accessed here. It provides age- and sex-stratified estimates of the burden of 333 leading causes of death and disability globally and for 195 countries and regions.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, namely:

  • Prioritising 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 20/02/16
     
  2. Hay SI, et al. Global, regional, and national disability-adjusted life-years (DALYs) for 333 diseases and injuries and healthy life expectancy (HALE) for 195 countries and territories, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet 2017;390:1260-1344.
     
  3. Practical guidance for assessment of disease burden at national and local levels. http://www.who.int/quantifying_ehimpacts/national/en/ - Accessed 20/02/16

 

 

© Helen Barratt, Maria Kirwan 2009, Saran Shantikumar 2018