Table 2.
Description of spatial exposure measures from extracted relationships and associations
| Concept | Measure | Description | Number of relationshipsa | Number of associations (n = 202)b | % of associations significant in the expected or unexpected directionc | |
|---|---|---|---|---|---|---|
| Availability | Continuous density | Euclidean kernel density estimation | A continuous density surface across a given area based on defined Euclidean kernels calculated using a probability density function | 3 | 18 | 61.1 |
| Variety | Road network buffer | Number of different outlets belonging to the same outlet category type within a defined area calculated using a road network radius from a reference location | 2 | 2 | 50 | |
| Count | Road network buffer | Number of outlets within a defined area calculated using a road network radius from a reference location | 26 | 68 | 44 | |
| Euclidean buffer | Number of outlets within a defined circular area calculated using a straight line radius from a reference location | 5 | 20 | 40 | ||
| Presence | Euclidean buffer | Binary presence/absence (1, 0) of outlets within a defined circular area calculated using a straight line radius from a reference location | 8 | 11 | 9 | |
| Road network buffer | Binary presence/absence (1, 0) of outlets within a defined area calculated using a road network radius from a reference location | 5 | 12 | 8 | ||
| Relative density | Euclidean buffer count/10,000 population | Number of outlets relative to another quantity within a defined circular area calculated using a straight line radius from a reference location | 9 | 13 | 7.7 | |
| Diversity | Euclidean buffer | Number of different outlet category types within a defined circular area calculated using a straight line radius from a reference location | 1 | 1 | 0 | |
| Retail food environment index | Euclidean buffer | Ratio of different outlet types within a defined circular area calculated using a straight line radius from a reference location | 1 | 1 | 0 | |
| Accessibility | Proximity | Euclidean distance | Straight line distance from a reference location to the nearest outlet | 7 | 11 | 36.4 |
| Road network distance | Road network distance from a reference location to the nearest outlet | 36 | 38 | 21 (2.6) | ||
| Average proximity | Road network distance | Average road network distance from a reference location to all outlets | 7 | 7 | (28.6) | |
aCount of the total number of relationships that employed a particular measure
bDunn (2012) [43] did not report on the technique used to determine proximity, count within a 1 mile buffer, and count within a 3 mile buffer. Therefore, these associations (n = 3) were excluded from the table
cThe percentage of unexpected associations is placed in brackets