1. South West Public Health Observatory Using GIS in Public Health Luke Hounsome South-West Public Health Observatory

2. South West Public Health Observatory Overview Summary of GIS basics Use of GIS in Public Health Data display Access to services Cluster analysis Conclusions

3. South West Public Health Observatory GIS basics I Fundamental principle of GIS is that any object has two types of information associated: Spatial and Attribute Spatial – grid reference, longitude/latitude Attribute – name, population, height These combine to allow powerful visual display of data, or analyse data based on geography

4. South West Public Health Observatory GIS basics II Geographical features can be represented in three main ways Point – Hospital location, case of disease Line – Roads, rivers Polygon – County, urban area, catchment area These are built up in layers, allowing comparison between various features using GIS software

5. South West Public Health Observatory GIS in public health GIS can help in Public Health in several ways: Highlight areas of good/poor health Identify clusters of disease (be careful !) Analyse access to services Help visualise spatial trends at a large level

6. South West Public Health Observatory Dr. John Snow’s map of cholera in London (1854)

7. South West Public Health Observatory Charles Dupin’s map of illiteracy in France (1826)

8. South West Public Health Observatory Thematic mapping for health Thematic maps are the most common output and can convey information relating to Range – highs/lows Spatial variation Geographical details – e.g. hospital locations Require some thought to avoid common mistakes Can be choropleth or isarithmic: each type has its advantages

9. South West Public Health Observatory Thematic mapping types Choropleth maps use pre-existing boundaries Ecological fallacy – grouping by area Can hide small pockets of interest Isarithmic maps use the data to define boundaries Requires more analysis work Could set boundaries to ‘prove’ an issue (MAUP)

10. South West Public Health Observatory Know your data I

11. South West Public Health Observatory Know your data II

12. South West Public Health Observatory Know your data III

13. South West Public Health Observatory Use reasonable colours

14. South West Public Health Observatory Scale is important

15. South West Public Health Observatory Scale is Important

16. South West Public Health Observatory Thematic maps can be interactive

17. South West Public Health Observatory Thematic maps online

18. South West Public Health Observatory Thematic maps – summary Select how you display your data carefully – what are you trying to show? Don’t overcomplicate maps – you may need to produce a couple Consider colours, what they can represent and how they match together (black and white) Urban areas can be difficult to display – consider ‘zooming- in’

19. South West Public Health Observatory Using GIS to calculate travel times A growing area of interest Setup a road network and then assign traffic speeds by class and urban/rural Software calculates the time taken to travel from a central point, and defines an isozone This can be used to calculate access to services or define a ‘catchment’ population

20. South West Public Health Observatory Travel times around UWE

21. South West Public Health Observatory Add population locations to travel times Population figures are often available by age-bands and sex If we can identify a point which is the proxy for the population location, we can map it to the isozones Population-weighted centroids have been calculated for LSOAs (small administrative areas) These are added to our previous map

22. South West Public Health Observatory Population locations mapped to travel times

23. South West Public Health Observatory Using the population data Determine which population points lie within each isozone Link to population figures, either within GIS software or externally Imagine UWE wishes to target local young people for a recruitment campaign

24. South West Public Health Observatory Results Based on 2006 populations from ONS, using age band 15- 19 MaleFemalePersons 10 minutes7287698614273 20 minutes145331376128294 30 minutes9718920318921 Totals315382995061488

25. South West Public Health Observatory Results analysis As the 20 minutes isozone is much larger, it covers a larger population However, the 30 minute zone covers more rural areas hence a lower population This often occurs around urban areas, which is why services such as hospitals are sited in cities rather than geographically central locations

26. South West Public Health Observatory Are travel-time/distance calculations overcomplicated? Is this use of software justified? Relatively time-consuming to set up and run Expensive; very important for public sector! Could a simpler approach be as good? Test this out using a fixed radius approach Approximate 20mph in town, 45 outside Draw circles at radius 3.33, 8.75 and 16.25 miles

27. South West Public Health Observatory Comparison of techniques

28. South West Public Health Observatory Results Simple methodRouteViewDifferenceDifference in Total vs Isochrones 10 minutes18481142734208 29% 20 minutes2607928294-2215-8% 30 minutes2145118921253013% Total660116148845237% It is probably worth using travel-time software if you can but this isn’t a bad start

29. South West Public Health Observatory Cluster analysis Plotting actual geographical locations can highlight patterns which are not otherwise obvious Must be careful not to try and find a reason for patterns we see – need to test a hypothesis Beware of the MAUP – Modifiable Areal Unit Problem Back up with other statistics

30. South West Public Health Observatory Looking at locations of deaths

31. South West Public Health Observatory Matching deaths to urban areas

32. South West Public Health Observatory Rates give a clearer picture

33. South West Public Health Observatory The MAUP – an example A fictional scenario….. Look at deaths around the Severn estuary A theory is postulated that pollution from the river is causing the deaths we have been considering A pressure group has analysed publicly available data and claims a higher rate of deaths adjacent to the river compared to Gloucestershire as a whole

34. South West Public Health Observatory The MAUP – an example

35. South West Public Health Observatory The MAUP – an Example

36. South West Public Health Observatory The MAUP – an Example

37. South West Public Health Observatory The MAUP – statistics Using the area 1 selection, a rate of 5.15 deaths per 1000 people is calculated This compares to a Gloucestershire average of 3.85 deaths per 1000 An increase? Area 2 has rate of 3.46 per 1000; but basically fulfils the same criteria

38. South West Public Health Observatory The MAUP - statistics The rates can be made to look quite different by subtle adjustments Define an area before testing a hypothesis – and stick to it! Back up with further statistical analysis: in this example the confidence intervals overlap, so we cannot say there is a true difference

39. South West Public Health Observatory Overall conclusions Using GIS in the field of Public Health can be helpful to: Highlight areas of concern Help people understand where these areas are Visualise general trends of an indicator versus location

40. South West Public Health Observatory Overall conclusions GIS can also be used to perform more complex analysis Population demographics/catchment area Access to services via. travel time Spatial Interpolation e.g. rainfall, air pollution

41. South West Public Health Observatory Sources of information For health data: http://www.nchod.nhs.ukhttp://www.nchod.nhs.uk For general statistics: http://neighbourhood.statistics.gov.ukhttp://neighbourhood.statistics.gov.uk For geographical boundary data: http://neighbourhood.statistics.gov.uk/dissemination/Info.do ?page=SOABoundaries.htm http://neighbourhood.statistics.gov.uk/dissemination/Info.do ?page=SOABoundaries.htm General geography information: http://www.statistics.gov.uk/geography/default.asp http://www.statistics.gov.uk/geography/default.asp