Health-based impact measures
A range of aggregate health metrics have been devised for use in assessing policy impacts or the effectiveness of health management systems. Many are also used as indicators for routine monitoring of health status at the national or international level. A number are summarised below.
Table 1. Some commonly used health-based impact measures
| Acronym | Description | Definition |
| LE | Life expectancy | Average number of years a new-born baby would survive, were he or she to experience the particular area's age-specific mortality rates for that time period throughout his or her life. |
| HLY | Healthy life years | Number of remaining years that a person of a certain age can be expected to live without disability. |
| YLL | Years of life lost | Total number of years of reduced life due to premature mortality: calculated as the number of deaths multiplied by a standard life expectancy at the age at which death occurs. |
| LLTI | Limiting long-term illness | Number of people affected by long-term illness, health problem or handicap which limits the daily activities or the work that a person can do. |
| YLD | Years living with disability | Number of years lived with a specified disease. |
| DALY | Disability adjusted life years | The sum of years of potential life lost due to premature mortality and the years of productive life lost due to disability. |
| QALY | Quality adjusted life years | How many extra months or years of life of a reasonable quality a person might gain as a result of treatment (particularly important when considering treatments for chronic conditions). |
Each of these measures may be useful in specific circumstances (e.g. depending on the range of health effects of intrest). DALYs, however, are generally the most relevant for integrated environmental health impact assessments, because they bring together, within a single measure, both morbidity and mortality effects, and take explicit account of both the duration and severity of morbidity and the timing of mortality (see link to QALYs and DALYs, below). Calculation of many of these measures can also be relatively complex, because of the need to estimate long-term effects, and to make allowance for underlying trends in life expectancy in the population. A calculation tool is therefore provided via the link below, which computes DALYs and several other key health impact measures .
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