Geographical Information System in Public Health

Dr. Mitasha Singh

Department of Community Medicine

DRPGMC, Tanda

Definition

• Geographical Information Systems (GIS) are a special class of information systems that keep track not only of events, activities, and things, but also of where these events, activities, and things happen or exist.

Source: Longley et al (2005) Geographic Information Systems and Science. 2nd Edition. John Wiley and Sons Ltd.

Dr. John Snowand the 1854 Cholera outbreak in London's Broad Street region

‘father of modern epidemiology’ and the ‘father of GIS’ because of the famous case of the 1854 Cholera outbreak in London’s Broad Street region.

• The map was made by Dr John Snow, who has conceived the hypothesis that cholera was transmitted through the drinking of polluted water, rather than through the air, as was commonly believed.

• He noticed that the outbreak appeared to be centred on a public drinking water pump in Broad Street – and if this hypothesis was correct, the pattern shown on the map would reflect the locations of people who drank the pump’s water.

Source: http://blogs.esri.com/Info/photos/geography_matters/images/1440/secondarythumb.aspx

• There were anomalies, in the sense that deaths had occurred in households that were located closer to other sources of water, but he was able to confirm that these households also drew their water from the Broad Street pump.

• Snow had the handle of the pump removed, and the outbreak subsided, providing direct causal evidence in favor of his hypothesis.

Source:http://www.gisdevelopment.net/application/health/overview/images/image1.jpg

• Spatial analysis- how the location in which events take place can have help us understand better the nature of phenomenon.

• At the time of the breakout, cholera was not understood to be geographically related. However, as soon as location of deaths was introduced into the picture it was clear that this was a geographical problem.

• Term GIS used for first time by Roger Tomlinson (1968) of the Department of Energy, Mines, and Resources

• Recent definition-• A computer system for the input, storage, maintenance,

management, retrieval, analysis, synthesis, and output of geographic or location-based information (spatial data).

• In the most restrictive usage, GIS refers only to hardware and software.

• In common usage, it includes hardware, software, and data. • When organizations refer to their GIS, this latter usage is

usually what they mean. • For some, GIS also implies the people and procedures

involved in GIS operation.

Federal Geographic Data Committee (US). Framework introduction and guide. Washington: The Committee; 1997.

GIS Terminology

• Geocoding– Append latitude and longitude to an address

• Centroid– Center of a region

• Layer– One type of geography on a map

• Features– Anything on a map

• Attributes– Characteristics of features

• Thematic mapping– Visualization of feature attributes

Functional components of GIS

• Data acquisition and verification

• Data storage and database management

• Data transformation and analysis

• Data output and presentation

Data acquisition and storage

• Spatial (geographic) data is needed -Data must be organized geographically/geocode the event -Records must include addresses or, -the region the point is located in (such as a zip code, census tract, etc.)

• Spatial database-• raster- Made up of pixels

No relationship between elements

• vector file format-

Points connected by lines

Data storage and database management

• Obtaining attribute data which must include geographical reference

• Relates to any public health issue of interest and can include disease information such as reported cholera cases, social data and environmental data.

Data transformation and analysis

• defines and executes spatial and attribute procedures to generate derived information.

• heart of a GIS

• Examples of analytical applications- • To identify the location of a target population based on the socio-economic

characteristics of individuals residing in a given community.• To identify a disease cluster and then to describe it’s characteristics in

terms of nearby health resources, risk factors, etc.

• Data transformation application- rely on the use of a GIS to transform a dataset or append variables to a dataset based on the spatial characteristics of records.

• For example-

1. appending the distance that each case resides from the location of a

known risk factor.

2. one layer in a GIS may contain the boundaries of health districts, while

another layer contains the residential point locations of individuals who

visited a clinic. By overlaying the two layers together, it is possible to

append the respective health district identifier to each of the individual

records in the database, solely on the basis of where they are physically

located on the map.

• Maintenance and transformation of spatial data- • input, manipulate, and transform data once it has been created.

• Examples of Spatial Database Queries-

• Identifying and locating disease clusters

• Locating target populations

• Identifying and locating community resources useful for intervention programs

Data output and presentation

Example of a Theme Map

• In this example of a theme map there are a total of 4 layers:– Layer Name Type of Layer– Zip Codes Region– Counties Region– Interstates Line– Hospitals Point

• Two of the layers have themes associated with them:• Zip codes have been color coded on the basis of the number of Myocardial

Infarctions per square mile which occurred during 1995. Red zip codes had at least 36.9 per square mile while the lowest category (blue) had under 6.2 per square mile.

• Hospitals have been sized based on the total number of beds at the hospital. Hospitals assigned the largest triangle size have at least 1,934 beds while hospitals which are the next largest size have at least 1,291 beds, etc.

Types of studies that can benefit from GIS

• Calculation and visualization of morbidity and mortality rates for regions-

• For developing rates- the case record- from a source such as a department of health services, vital statistics, clinics, etc.,

• denominator for the rates- from census data or from a demographic data vendor.

• case records must be aggregated to the regional level and then be appended to the regional attributes.

• Age can be controlled for by creating separate attribute fields for population by age and for the numbers of cases by age.

• Calculation of distance variables for statistical testing

• when a distance variable is to be calculated so that further analysis can be performed with a statistical analysis program

• For example- hypothesis- the closer an individual with TB resides to a clinic, the more likely they are to comply with the full course of TB treatment.

• the distance that each individual resides from the nearest clinic must be calculated and appended to the record which also contains the treatment status.

• the record must be geocoded and placed as a layer in a GIS program.

• the locations of all clinics providing TB treatment must also be geocoded and placed into another layer.

• The GIS software can then be used to calculate the distance of each TB case to the nearest clinic and populate the appropriate field with that value.

• Append the distance

• table loaded into a statistical analysis program to statistically test the association between the distance variable and the patient compliance.

• Disease cluster analysis– Locating larger than expected incidences of a disease

related by time and place

Commonly Used GIS Programs

• Atlas GIS (ESRI)• ArcView GIS (ESRI)• ArcInfo GIS (ESRI)• MapInfo (MapInfo)• EpiMap GIS

Advantages

• GIS technology improves the ability of practitioners, planners, and researchers to organize and link datasets (for example, by using geocoded addresses or geographic boundaries).

• Ability to link datasets can help public health practitioners plan more cost-effective interventions.

• GIS technology provides public health practitioners and researchers with several new types of data.

• Public health practitioners can also explore the utility of data collected by marketing firms about consumer spending patterns, retail expenditures, and lifestyle segmentation profiles.

• Diagnose and investigate a health hazard in community.

• GIS technology encourages the formation of data partnerships and data sharing at the community level.

• Maps developed using GIS technology-

- display large amount of information in easily understandable form

- can be an extremely effective tool to help community decision makers

visualize and understand a public health problem.

• Remote sensing and Global positioning system has been integrated under the GIS umbrella for disease surveillance, situation analyze and the spatial modelling of disease transmission. 

• Evaluate effectiveness, accessibility and quality of health services.

Application of GIS- Infectious diseases

• Distribution of cases and association with environmental conditions

• Models to predict risk of infection

• Investigation of an outbreak

• Predict spread of epidemic on the basis of movement of people

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Access to health care health planning

• Utilization of healthcare is inversely proportional to distance from health facility

• Access to-

primary health care

maternal health care

cancer

emergency transport

Risk assessment

Proof of association

• Distribution of risk factors

• Distribution of disease or health conditions

• Collaborative evidence

• Helpful for predictions

Health monitoring and decision making

• used for mapping the biodiversity• ecology of vectors, • disease prevalence,• disease transmission, • spatial diffusion. • It has been used for monitoring the past, present, and

future disease control programs • Example- The national mass drug administration programs in different

states aim toward the elimination of filariasis disease in India.

Limitations

• Complex data is easy to understand but simple picture is subjected to ecological fallacy.

• Sometimes serious distortions in visual images suggest conclusions that would not be supported by careful epidemiological analysis.

• Aggregation bias- failing to identify the true nature of cause effect relationships at level of individual.

• Atomistic fallacy- failing to consider the context in which individual behavior occurs.

• High priced software and their non availability at multiple locations.

• Capacity of public health researchers to use GIS and remote sensing technologies to analyze and interpret data

• Privacy and confidentiality issues- maps may contain sufficient detail so that individual cases can be identified.

Primarily an issue when maps are released to the public or included in

published work.

thank you