new methods for measuring access to food sources

UW-CORUW Center for Obesity Research

Urban Form Lab

New Methods For Measuring Access To Food Sources

Philip Hurvitz, PhCUrban Form LabCollege of Architecture & Urban PlanningUniversity of Washington

Research to Policy Briefing with Food Standards, Australia/New Zealand

September 6, 2007

UW-COR Slide 2 (of 19) PMH

Overview

Importance of location in public health Typical representations of location Fine-scaled approaches to

representation and analysis of location Future directions in spatial

representations for public health surveillance and intervention


Overview





Importance of location in epidemiology & public health “…the curse causeless shall not come”

–Proverbs 26:2 Exposure to disease-causing conditions

and agents is spatially and temporally bound

Epidemiology is fundamentally a spatial science

Has medical scienceignored location inrecent decades?


Importance of location in epidemiology & public health Epidemiology and public health are interested

in population-wide effects, … but … Population-wide effects can only be

ascertained from individual-level measurements

GIS allows the measurement of individual characteristics within an explicitly spatial context

If location is an important factor in a public health issue, GIS should be incorporated as a data management and analysis tool


Overview





Typical representations of location

Area-based representations are popular Easily created from simple statistical

tables and base map geographic files

http://go.worldbank.org/DL057HBF30

http://www.cdc.gov/nccdphp/dnpa/obesity/trend/maps/

Obesity by state, 2006


Typical representations of location

Large area-based maps tell us little about the exposure → disease causal chain

Aggregated data ignore the spatial nature of individualistic exposure (MAUP)

this tract is high in FF density

this tract has FF density of 0


Overview





Fine-scaled approaches to representation and analysis of location “Public” data sources can be used for

location source data

PHSKC data

Yellow Pages data


Fine-scaled approaches to representation and analysis of location Geocoding of individual locations can

be useful Knowledge of specific locations of

agents of exposure may be informative beyond simple spatial aggregation

this tract is high in FF density

does this tract have an effective FF densityof 0?


Fine-scaled approaches to representation and analysis of location Use of newer spatial analysis methods Interpolation techniques (e.g. kernel density

estimator, KDE) can estimate exposures at any location in

space not limited to arbitrary administrative

boundaries this tract has arelatively high

effective FF density


Fine-scaled approaches to representation and analysis of location

Use of fine scaled data sources

Tax-lot-level data are detailed and varied

Variation at the household-unit population level is maintained and can be used for analytical purposes0 200 400100 m[

property value

< 100K

100-250K

250-500K

500K-1M

1-2M

> 2M

Wallingford Parcels


0 200 400100 m[

property value

< 100K

100-250K

250-500K

500K-1M

1-2M

> 2M

Wallingford Parcels

Fine-scaled approaches to representation and analysis of location

Census data lack detail and variation

Within-tract variation is lost as geometries become larger and more aggregated

Boundaries may lack meaning

mean property value

< 100K

100-250K

250-500K

500K-1M

1-2M

> 2M

Wallingford Census Tracts

0 200 400100 m[


0 2000 4000 6000 8000

0.0

e+

00

1.0

e+

07

2.0

e+

07

Individual Parcel Value (n=8875)

valu

e (

$)

Fine-scaled approaches to representation and analysis of location Fine-grain disaggregate data give much

greater statistical power for linking SEP, exposure, and disease

1 2 3 4 5 6 7 8

25

00

00

35

00

00

45

00

00

Tract Mean Parcel Value (n=8)

valu

e (

$)

Rank order by value Rank order by value


Fine-scaled approaches to representation and analysis of location Measurement of physical activity and

location in real time (1 s, 3-7 m precision)


Fine-scaled approaches to representation and analysis of location Measurement of energy balance in real

time, providing information about healthy food choice and physical activity enhancing locations


Overview





Future directions in spatial representations for public health surveillance and intervention Partnerships among researchers, public

health agencies, local governments, and health care providers for surveillance and intervention

Transdisciplinary research teams (urban planning, epidemiology, computer science

Spatially explicit data sources available from top down and generated from bottom up

New analytical methods to handle multiple and high-resolution data sources

new methods for measuring access to food sources

Documents

spatial representations

public health surveillance

finescaled approaches

overviewimportance of

spatial contextif location

based representations

public health issue

analysis of locationuse