South-East Asia Regional Conference on Epidemiology

Uses and development of Geographic
Information System (GIS) technology in
epidemiological research
Mark Daniel
The use of Geographic Information System (GIS) technology in environmental and population health
research is increasing (1,2). The influence of different levels of environmental exposures, the nature
of these exposures and individual-level socio-demographic, psychosocial and behavioural effects on
public and population health outcomes are increasingly being studied using GIS (3-6). The aims of
the MEGAPHONE® GIS (Montreal Epidemiological and Geographic Analysis of Population Health
Outcomes and Neighbourhood Effects) (7), developed with the support of the Canada Foundation
for Innovation, are to determine which environmental risk conditions are robustly related to health
outcomes and to elucidate how these effects are expressed. The identification of environmental
factors, both important and changeable, can provide an evidence base for policy interventions on
services and resources needed for healthful living. Environmental intervention can enable healthful
behaviour, e.g. provision of outlets for fresh fruit and vegetables or efficient public transportation can
positively influence diet and active transport involving incidental physical activity. Other actions may
include strategies to improve the quality of air and water or noise reduction.
Environmental risk conditions function at the level of communities or populations. They are the
conditions of living and health-related resources and opportunities available to a population. They can
be specific to a geographical area (e.g. the availability, accessibility and affordability of healthful food
for a given community) or they can exert broad effects at the macro-social level (e.g. institutionalized
racism or restricted economic opportunity) (8). They are expressed as contextual measures of places
(e.g. housing quality, social disorder or the availability and accessibility of goods and services) and as
compositional measures of population attributes (e.g. aggregated educational attainment or income).
Relevance of environmental factors
It is a tenet of public health that environmental and lifestyle or behavioural factors are reciprocal in
their relationships to each other and hence influence health indirectly and directly (Fig. 1). By this
logic, the lifestyles and health status of populations cannot be understood or targeted for improvement
without attention to environmental factors. The principle underlying the focus on environmental
risk conditions is that the causes of individual cases are not the causes of incidence (9). Causes of
cases are individual risk factors whereas causes of sick populations (incidence) are environmental
risk conditions. This can be shown by contrasting different populations in their distributions of risk
factors and disease. Much epidemiological research has, however, implicitly or explicitly, attributed
diseases for which there are known behavioural components to individual causes. This disregards
that the population distribution of risk is inherently a function of environmental factors, including the
norms, resources, opportunities and living conditions that define a population. A biological ‘norm’ or
‘deviations’ cannot be defined without reference to specific populations and their characteristics (10).