GIS and Health Geography - UBC Department of Geographyibis.geog.ubc.ca/courses/geob479/notes/Handouts/Lecture06.pdf · GIS and health geography ... spatial dimension, therefore. More

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GIS and Health Geography

What is epidemiology?

GIS and health geography Major applications for GIS

Epidemiology What is health (and how location matters) What is a disease (and how to identify one) Quantifying disease occurrence

Incidence vs prevalence Identifying the population Working with small area data

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A GIS can be a useful tool for health researchers and planners because, as expressed by Scholten and Lepper (1991):

Health and ill-health are affected by a variety of life-style and environmental factors, including where people live. Characteristics of these locations (including socio-demographic and environmental exposure) offer a valuable source for epidemiological research studies on health and the environment. Health and ill-health always have a spatial dimension, therefore. More than a century ago, epidemiologists and other medical scientists began to explore the potential of maps for understanding the spatial dynamics of disease.

GIS and health Geography

1. Spatial epidemiology

2. Environmental hazards

3. Modeling Health Services

4. Identifying health inequalities

Major applications for GIS

Spatial epidemiology is concerned with describing and understanding spatial variation in disease risk.

Individual level data Counts for small areas

Recent developments owe much to: Geo-referenced health and population data Computing advances Development of GIS Statistical methodology

Spatial epidemiology

Population is unevenly distributed geographically.People move around (day-to-day movements;

longer term movements including migration).People possess relevant individual characteristics

(age, sex, genetic make-up, lifestyle, etc).People live in communities (small areas).

Framework for analysis

Provides a qualitative answer about the existence of an association (e.g. between environmental variable and health outcome).

May provide evidence that can be followed up in other ways.

Why small area analyses?

These studies typically involve examining geographical variations in exposure to environmental variables (air, water, soil, etc.) and

their association with health outcomes while controlling for other relevant factors using regression.

Geographical correlation studies

Issues: Spatial misalignment

Frequency and quality of population data (e.g. Census every 5/10 years).

Spatial compatibility of different data sets.Availability of data on population movements.Measuring population exposure to the

environmental variable.Environmental impacts are often likely to be quite

small (relative to, for example, lifestyle effects) and there may be serious confounding effects.

Cannot estimate strength of an association.Ecological (or aggregation) bias.

Issues: Uncertainty

Allow for heterogeneity of exposure.Use well defined population groups.Use survey data to help obtain good

exposure data.Allow for latency times.Allow for population movement

effects.

Issues: Best practices(Richardson 1992)

Dr. John Snows Map of Cholera Deaths in the SOHO District of London, 1854

Spatial epidemiology

Environmental hazards

Hazard Surveillance

Hazardous agent present in the environment

Route of exposure exists

Exposure Surveillance

Host exposed to agentAgent reaches target tissueAgent produces adverse

effect

Outcome Surveillance

Effect clinically apparent

Environmental hazards

GIS: Identify causal and mitigating factors

A generic index of accessibility/ remoteness for all populated places in non-metropolitan Australia.

A model which allows accessibility to any type of service to be calculated from all populated places in Australia.

ARIA (Accessibility/Remoteness

Index of Australia)

https://www.health.gov.au/internet/main/publishing.nsf/Content/health-historicpubs-hfsocc-ocpanew14a.htm

AIRA

https://www.health.gov.au/internet/main/publishing.nsf/Content/E2EE19FE831F26BFCA257BF0001F3DFA/$File/ocpanew14.pdfhttps://www.health.gov.au/internet/main/publishing.nsf/Content/E2EE19FE831F26BFCA257BF0001F3DFA/$File/ocpanew14d.pdfhttps://www.health.gov.au/internet/main/publishing.nsf/Content/E2EE19FE831F26BFCA257BF0001F3DFA/$File/ocpanew14d.pdf

Mortality rate of infants

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Metro.

Rural

Remote

Geo

grap

hica

l loc

atio

n

Mortality Rate / 1000 live births

non-AboriginalAboriginal

Where do infants and children die in WA? 1980-2002 Jane Freemantle, PhD. November 2004

Chart5

17.95.9

18.56.5

23.96.8

Aboriginal

non-Aboriginal

Geographical location

Mortality Rate / 1000 live births

infan_Ab status ALL_inf nn pnn

Infant mortality 1980-2002, by Aboriginal status

Aboriginalnon-AboriginalRR

1980-1984258.42.98

1985-1989257.63.27

1990-199420.15.63.61

1995-199716.94.43.83

1998-200116.13.74.4

ALL

infantneonatalpostneonatal

1980-19849.25.53.5

1985-19898.65.43.3

1990-19946.43.62.7

1995-19975.13.22.1

1998-20014.52.71.8

ALL inf neo post mortality 1980-2002

infan_Ab status ALL_inf nn pnn

Aboriginal

non-Aboriginal

RR

Birth year group

Rate/1000 live births

nn pnn_Ad stats

NND and PND by Abstatsus 1980-2002

Ab.-neonatenon-Ab.-neonateAb.-postneonon-Ab.-postneo

1980-198415.55.259.723.14

1985-198910.225.0814.732.61

1990-19948.53.4711.922.15

1995-19977.222.959.71.6

1998-20017.42.38.81.3

infant

neonatal

postneonatal

Birth year groups


nn pnn_Ad stats

Ab.-neonate

non-Ab.-neonate

Ab.-postneo

non-Ab.-postneo

Birth year groups


location

ALL

MetroRuralRemote

1980-19848.39.415

1985-19897.98.512.9

1990-19945.87.19.7

1995-19974.95.17.1

1998-20013.7512.3

Ab.metronon-Ab.metroAb.ruralnon-Ab.ruralAb.remotenon-Ab.remote

1980-198418.58.117.48.932.610

1985-198923.27.624.87.4268.7

1990-199419.35.4186.3225.7

1995-199716.64.610.54.720.32.5

1998-200112.13.518.33.918.14.9

RRnon-Aboriginal cf non-Aboriginal

Remote cf metroRemote cf ruralRural cf metro

1980-19841.241.131.1

1985-19891.171.221

1990-19941.10.91.2

1995-19970.60.50.3

1998-20011.41.31.1

RRAboriginal cf Aboriginal

Remote cf metroRemote cf ruralRural cf metro

1980-19841.81.90.9

1985-19891.21.11.1

1990-19941.11.20.9

1995-19971.220.6

1998-20011.511.5

CMR - 1980-2001

Aboriginalnon-AboriginalRR

Metro.17.95.93

Rural18.56.52.9

Remote23.96.83.5

location

Metro

Rural

Remote

Birth year group


Ab.metro

non-Ab.metro

Ab.rural

non-Ab.rural

Ab.remote

non-Ab.remote

Birth year group


Ab.metro

non-Ab.metro

Ab.rural

non-Ab.rural

Ab.remote

non-Ab.remote

Birth year groups


*

Remote cf metro

Remote cf rural

Rural cf metro

Birth year groups

Relative risk of death

Remote cf metro

Remote cf rural

Rural cf metro

Birth year groups

Relative risk of death

Aboriginal

non-Aboriginal

RR

Geographical location

Rate/1000 live births& RR

Identifying health inequalities:Well-known relationship 25% 50% of observed gradient due to risk factors like smoking,

hypertension and diabetes in lower socio-economic groups (Marmot et al.,1997)

Access to healthcare (Bosma et al., 2005) Imbalance between workplace demands and economic reward

(Lynch et al.,1997) Poor education, lower levels of health literacy, low birth weight

(Marmot, 2000)

Relationship may vary with gender, with the association thought to be stronger in males (Thurston, 2005) (should we question this?)

SES and Heart disease

Number of daily hospital discharges (Y) with Ischemic Heart Disease (IHD) where admission had been via emergency room for 591 postcodes in NSW Every day from July 1, 1996 to June 30, 2001 Males and females 5-year age increments

Denominator (N) obtained from censusSocial disadvantage measured at postal area level

using the census-derived SEIFA (Socio-Economic Indexes for Areas) index

The Data

High values indicate social advantage

SEIFA distribution in NSW

NSW IHD rates




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The study of the distribution and determinants of health and disease-related states in populations, and the application of this study to control health problems.

the product of [epidemiology] is research and information and not public health action and implementation (Atwood et al. 1997)

epidemiologys full value is achieved only when its contributions are placed in the context of public health action, resulting in a healthier populace. (Koplan et al. 1999) (Source: Rutgers)

What is epidemiology?

http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCwQFjAA&url=http://dimacs.rutgers.edu/BMC/TeacherMaterials/Introduction%20to%20Epidemiology%20and%20the%20Modules.ppt&ei=XLUWU6aVI4OBogTIvILQAw&usg=AFQjCNETuiEEoMB4wlHVLet6l-ceuYV9hA&sig2=yq9QVzs6KhBRofuAXSxxaQ&bvm=bv.62286460,d.cGU&cad=rja

Epidemiologic approaches

DESCRIPTIVE Health and disease in the communityWhat? Who? When? Where?What are thehealth problemsof the community?

What are theattributes of these illnesses?

How many peopleare affected?

What are theattributes ofaffected persons?

Over whatperiod of time?

Where do theaffected peoplelive, work orspend leisuretime?

ANALYTIC Etiology, prognosis and program evaluation

Why? How?What are the causal agents?

What factorsaffect outcome?

By what mechanism do they operate?

Dorland's Illustrated Medical Dictionary (28th ed.):

Health "a state of optimal physical, mental, and social well-being, and not merely the absence of disease and infirmity.

Disease "any deviation from or interruption of the normal structure or function of any part, organ, or system (or combination thereof) of the body that is manifested by a characteristic set of symptoms and signs . . .".

What are health and disease?

Health, as defined in the World Health Organization's Constitution, is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity."

Health is seen as more than just the absence of disease, and depends upon a complex suite of factors, with location taking the lead. A location is more than just a position within a spatial frame (e.g., on the surface of the Earth or within the human body).

Different locations on Earth are usually associated with different profiles: physical, biological, environmental, economic, social, cultural and possibly even spiritual profiles, that do affect and are affected by health, disease and healthcare. (Source: Dr. M. N. Kamel Boulos)

What is health

http://healthcybermap.org/HGeo/index.htm

An example of how location matters and carries with it other factors into play: The body weight of infants at birth is one readily available

piece of data, and the relationship between low birth-weight and maternal and child health is a continuing line of research.

In New York City, Sara McLafferty and Barbara Tempalskihave studied the spatial distribution of low birth-weight infants and identified areas in which the number of low birth-weight infants increased sharply during the 1980s.

Their results indicated that the rise in low birth-weight was closely linked to women's declining economic status, inadequate insurance coverage and prenatal care, as well as the spread of crack/cocaine.

Location and health

Location and health

http://healthcybermap.org/HGeo/pg1_2.htmhttp://healthcybermap.org/HGeo/pg1_2.htm

Location and health




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Manifestional criteria: refer to symptoms, signs, and other manifestations of the condition. Defining a disease in terms of manifestational criteria relies on the proposition that diseases have a characteristic set of manifestations. This defines disease in terms of labeling symptoms.

Causal criteria: refer to the etiology (cause) of the condition, which must have been identified in order to be employed. This defines disease in terms of underlying pathological etiology.

What is disease

How do you identify a disease?

The Acquired Immunodeficiency Syndrome (AIDS) was initially defined by the CDC in terms of manifestational criteria as a basis for instituting surveillance.

The operational definition grouped diverse manifestations Kaposi's sarcoma outside its usual subpopulation, PCP and other opportunistic infections in people with no known basis for immunodeficiency.

This was based on similar epidemiologic observations (similar population affected, similar geographical distribution) and a shared type immunity deficit (elevated ratio of T-suppressor to T-helper lymphocytes).

Manifestational Criteria

Around 1984 Human Immunodeficiency Virus (HIV, previously called human lymphotrophic virus type III) was discovered and demonstrated to be the causal agent for AIDS.

AIDS could then be defined by causal criteria.

Causal Criteria

http://www.nejm.org/doi/full/10.1056/NEJMp038194

A single causal agent may have multiple clinical effects.

Multiple etiologic pathways may lead to apparently identical manifestations, so that a manifestationally-defined disease entity may include subgroups with differing etiologies (equifinality).

Not all persons with the causal agent develop the disease (e.g., Typhoid Mary).

Challenges with Disease Classifications

http://en.wikipedia.org/wiki/Equifinalityhttp://en.wikipedia.org/wiki/Typhoid_Mary

UnderlyingGeneticSusceptibility

Onset ofdisease

Diagnosisof disease

Environmental & Behavioral Factors(Spatial dependence)

PhysiologicAbnormalities Clinical disease

Cause-specificmortality

XSub-clinical disease

The natural history of disease



Incidence versus prevalence Identifying the population Working with small area data

TOC

To study disease, we need measures of its occurrence.

Some measures of disease occurrenceCountsPrevalence IncidenceMortality

Measures of disease occurrence

Epidemiologic approaches

DESCRIPTIVE Health and disease in the communityWhat? Who? When? Where?What are thehealth problemsof the community?What are theattributes of these illnesses?

How many peopleare affected?

What are theattributes ofaffected persons?

Over whatperiod of time?

Where do theaffected peoplelive, work orspend leisuretime?

Each of the measures can be calculated for different combinations of What? Who? When? and Where?

Each of the Ws needs to be defined carefully to get comparable measures across a province or state, a nation, the world.

Incidence and prevalence measure different aspects of disease occurrence

Prevalence Incidence

Numerator:

Denominator:

Measures:

Most useful:

Incidence and Prevalence

All cases, no matter how long diseased

Only NEW cases

All persons in pop Only persons at risk of disease

Presence of disease Risk of disease

Resource allocation Risk, etiology

Etiology: the study of a diseases causes.

Numerator Number of deaths

Denominator Number of individuals in

population (how defined?)

Time interval 1-year: Annual Mortality Rate

(typical to use an annual rate)

Specifier age, sex, race, etc.

Mortality Rate Incidence of death

Mortality rates

Prevalence numerator case definition

Result ofnew definition

1st Quarter of 1993:Expansion of

surveillance casedefinition

AIDS cases, United States 1984-2000

Understanding population dynamics is crucial to epidemiolog y.

Demography = the study of population dynamics including fertility, mortality and migration

The demi in Epidemiology

English

epi among

demos people

logy study




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Developing multi-level models for spatially-correlated data requires confidence in the dependent data.

Data for disease mapping often consists of disease counts and exposure levels in small adjacent geographical areas.

The analysis of disease rates or counts for small areas often involves a trade-off between statistical stability of the estimates and geographic precision.

Data considerations

Spatial Analytic Techniques for Medical Geographers (Albert et al., 2000)

Methodological toolboxes



Incidence versus prevalence Identifying the population Working with small area data

Summary

GIS and Health GeographyTOCGIS and health GeographyMajor applications for GISSpatial epidemiologyFramework for analysisWhy small area analyses?Geographical correlation studiesIssues: Spatial misalignmentIssues: UncertaintyIssues: Best practicesSpatial epidemiologyMajor applications for GISEnvironmental hazardsEnvironmental hazardsMajor applications for GISARIA (Accessibility/Remoteness Index of Australia)AIRAMortality rate of infantsSES and Heart diseaseThe DataSEIFA distribution in NSWNSW IHD ratesTOCWhat is epidemiology?Epidemiologic approachesWhat are health and disease?What is healthLocation and healthLocation and healthLocation and healthTOCWhat is diseaseManifestational CriteriaCausal CriteriaChallenges with Disease ClassificationsThe natural history of diseaseTOCMeasures of disease occurrenceEpidemiologic approachesIncidence and PrevalenceMortality Rate Incidence of deathMortality ratesPrevalence numerator case definitionThe demi in EpidemiologyTOCData considerationsMethodological toolboxesSummary

GIS and Health Geography - UBC Department of Geographyibis.geog.ubc.ca/courses/geob479/notes/Handouts/Lecture06.pdf · GIS and health geography ... spatial dimension, therefore. More

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