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The Vancouver Island Health Authority uses geographical information systems (GIS) to map health statistics. You can view several choropleth maps displaying this data by clicking on the links listed on the left-hand menu.
Choropleth maps display patterns or intensities in different areas by shading them different colours. They are widely used in health mapping for a number of reasons:
- The majority of health and demographic data is only released by area.
- By not showing precise locations, these maps avoid concerns about privacy and confidentiality.
In this instance, the local health area (LHA) is the administrative area used to map the data. Choropleth maps give the impression of uniformity within areas and show sharp changes between areas, even though the underlying distribution may change gradually or continuously. The map’s appearance and the message it conveys vary depending on the size, number, and configuration of area units mapped. For example, small area units are more likely to capture the underlying pattern of health events, while large areas conceal local differences. The scale of area units affects our perceptions and understanding of health patterns.
Data Definitions
SMR (Standardized Mortality Ratio) - The ratio of the number of deaths occurring to residents of a geographic area to the expected number of deaths in that area based on provincial age-specific mortality rates. With reference to the maps, a value greater than 1 indicates that the Local Health Area experienced a greater number of deaths than expected. A value less than 1 indicates that the Local Health Area experienced fewer deaths than expected. The number of deaths expected is determined provincially.
PYLL (Potential Years of Life Lost) - The number of years of life lost when a person dies before a specified age (75 years). All deaths are assumed to occur at the midpoint of five-year age groups. This technique considers the age of death rather than the mere event of death, as it allows assigning a different weight to deaths that occur at different moments of life. The objective of this indicator is to provide a wider view of the relative importance of the most relevant causes of premature mortality. It is used primarily in the planning and definition of health priorities.
Low Birth Wt. - Any live born infant weighing less than 2500 grams.
Pre-Term - Any live born infant less than 37 week gestation at delivery.
Teenage Mother - Any mother who was 19 years of age or younger at time of delivery of a live born infant.
Elderly Gravida - Any mother who was 35 years of age or older at time of delivery of a live born infant.
Stillbirth - Any birth of a dead child or fetus.
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