Proportional mortality ratio:
The proportional mortality ratio (PMR) is the proportion of the number of deaths attributed to a specific cause and the total number of deaths, expressed in percentages. About 80% of the deaths in Belgium occur among elderly (65 years and older); the specific causes of death of this group have a decisive influence on the overall mortality. The study of the PMRs for all ages gives a good image of the main causes of death among elderly, but also masks those causes that occur at a younger age. Therefore, the PMR was calculated for the following age groups: 1-14 years, 15-24 years, 25-44 years, 45-64 years and 65 years and older.
Age and sex are important factors when studying the mortality statistics. For the comparison of mortality rates between the Belgian regions, the data were standardised for age and/or sex, with the distribution of age of either the Belgian, the European or the World population as reference groups. For the comparison of districts, the mortality rates were standardised for sex and age, with as reference group the specific mortality rates by sex and age of either the Belgian, the Flemish, the Walloon or the Brussels population: indirect standardisation or SMR (Standardised Mortality Ratio). The number of observed deaths is calculated as compared to the number of expected deaths based on specific mortality rates by sex and age at national level. An SMR smaller than 100 means that the number of observed deaths at the level of the district is smaller than what was expected when the mortality rate at the national level was applied to the concerned district.
Potential years of life lost (PYLL):
This indicator is used to measure the importance of premature causes of death. The number of years lost before the age of 65 years for example, as death occurs at age X, is calculated using the formula "65 - X". Then, the total PYLL for a specific cause of death is divided by the number of exposed person years.
The theoretical increase in the number of life years after 100% elimination of the mortality due to a specific cause of death is an indicator based on the comparison of two life expectancies at birth (summary life tables are used to calculate the life expectancy): one is (as usually) calculated from the risk of mortality by age group and the other is estimated after elimination of mortality by a specific cause of death (or a group of physiologically related causes). This leads to the assumption that the risk of death by this specific cause is independent of other causes of death.