Disease Burden - Estimating The Burden

Estimating The Burden

WHO developed a methodology to quantify the health state of a population using summary measures of population health (SMPH), which combine information on mortality and non-fatal health outcomes. The SMPH can be divided into two distinct categories: the measures of health gap and measures of health expectancies. The most commonly used is the DALY.

The exposure-based approach, which measures exposure via pollutant levels, is used to calculate the environmental burden of disease. This approach needs the following data:

• Identification of outcomes associated with the relevant risk factor
• Assessment of exposure in the study population
• Exposure distribution of the study population
• Dose-response relationships

A dose-response relationship is a function of the exposure parameter assessed for the study population. Exposure distribution and dose-response relationships are combined to yield health impact distributions in the study population. Health impact distributions, usually expressed in terms of incidence, can then be converted into health summary measures, such as DALYs. Exposure-response relationships for a given risk factor are commonly obtained from epidemiological studies, and the derived attributable fractions are then applied to disease burden, expressed in deaths or DALYs, associated with the risk factor. For example, the disease burden of outdoor air pollution for Santiago, Chile, was calculated by measuring the concentration of atmospheric particulate matter (PM10), estimating the susceptible population, and combining these data with relevant dose-response relationships. A reduction of particulate matter levels in the air to recommended standards would cause a reduction of about 5200 deaths, 4700 respiratory hospital admissions, and 13,500,000 days of restricted activity per year, for a total population of 4.7 million.

In 2002, WHO estimated the environmental burden of disease globally by using a combination of comparative risk assessment data and expert judgment to develop environmentally attributable fractions (EAFs) of mortality and morbidity for 85 categories of disease.

In 2007, WHO released the first ever country-by-country analysis of the impact environmental factors have on health for its then 192 member states. These country estimates were the first step to assist national decision-makers in the sectors of health and environment to set priorities for preventive action. It is divided into three parts: