Question

What does global burden of a disease mean? Explain how global health researchers tend to measure how significant a health issue is (that is, its global burden and list some methods used for estimating disease burden in the population.

Answer 1

Global burden of disease- Meaning

Global burden of disease is a statistical measure indicating loss of years of healthy life through disabling      disease in a specified population, as measured in DALYs.

Methods to measure global burden of disease

• 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 . 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:

Health-Adjusted Life Years (HALYs) are summary measures of population health used in burden of disease estimates. They combine the effects of disability or disease (morbidity) and death (mortality) simultaneously. HALYs, an umbrella term for a number of such summary measures, allow for comparisons to be made across illnesses, interventions, and populations. The data are normally presented by age, sex, and region.

To calculate the HALYs of a disease, three general steps are required. A researcher must:

1. Describe the associated state of health (“health state”) or disease conditions;

2. Develop numerical values for the health state or condition;

3. Combine the numerical values of each health state with estimates of life expectancy.

• Estimating Quality-Adjusted Life-Years (QALY) QALYs represent statistical values ascribed to health outcomes, both in terms of quantity and quality.

It takes 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 while a year of complete functional impairment (e.g. death) has a QALY of 0. It is measured by asking respondents to assess which health states are more valuable to them.

• Estimating 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.

DALY= Years of life lost due to premature mortality (YLL) + Years lived with disability (YLD)

          YLL = N x L

Where:

N=number of deaths

L = standard of life expectancy at age of death in years

          YLD= I x DW x L

Where:

I = number of incident cases

DW = disability weight

L = average duration of the case until remission or death (years)

Data Required to Calculate Burden of Disease:

HALYs, including DALYs and QALYs, are based on the latest available epidemiological data.

To measure HALYs the following information is required:

• Mortality (number of deaths)

• Disease incidence

• Health state distribution

• Health state duration

• Weights associated with each health state.

The information needed can be retrieved from different sources: vital statistics, data from reportable diseases, healthcare utilization data, country censuses, national and local surveillance data, verbal autopsies (in countries where they are used), hospital records, surveys (e.g. road safety surveys, institutional survey, household survey, health survey, etc.), police records, death certificates and mortuary records.