De Facto population density and the location of AEDs: Are they proportional to each other?

Is the spatial distribution of AEDs proportional to the static population or the De Facto population?

The purpose of this study is to investigate the correlation between the distribution of automated external defibrillators (AED) installed in public spaces and the population density in Seoul.

Unlike the past, when the residential population could only be measured by the census, real-time populations (de facto populations) can now be measured by smartphone signal data. This study aims to compare the spatial distribution of AEDs in Seoul, the residential population, the working population, the number of local businesses, and the de facto population.

The analysis utilizes the Seoul Living Population data set, which is collected through personal mobile GPS location data.

On a daily basis, the Seoul Metropolitan Government provides data collected from the population of 19,153 census tally districts in Seoul by dividing the number of populations located in the districts of each 24-hour unit by sex and age (5-year interval, all ages from 0 to 69 and over 70).

This information is based on LTE (Long Term Evolution, a 4G mobile communications standard) signal data provided by KT (Korea Telecom). It is recorded at the point of time when either a base station is changed or data are used, regardless of whether users utilizes their mobile phones.

Thus, Seoul Living Population differs from the concept of floating population in the sense that it is a de facto population that exists at the time of measurement. Therefore, it is not identical to the census data, and it is not limited to a static location.

The National Emergency Medical Center (NEMC) and Ministry of Health and Welfare has installed AEDs in public places to provide first aid for sudden cardiac arrests. In the Seoul area, a total of 4,336 AEDs have been installed. The location data of each unit are obtained from the NEMC[1] website.

<Figure 1> [1]

Then, each location of an AED unit is geocoded into the Katec coordinate system, EPSG 1841 (Vessel Ellipsoid) using GIS – as in <Figure 2>.

<Figure 2> The location of AED units in Seoul

A multiple linear regression (robust SE) analysis was conducted using AED density (the number of AEDs per each census tally unit area) as the dependent variable, and the density of the residential population, working population, local businesses, and the de facto population as the independent variables.

Results show that only the residential population density was significant among the variables. They also suggest that the spatial distribution of AEDs is only correlated with the residential population density. Thus, they imply that the location of each unit was originally determined by the residential population density, not by worker, business, or de facto population density.

<Table 1> Analysis result: Multiple linear regression (Robust SE)

The location of AEDs is critical in first aid situations. Their distribution should be proportional to the population density (TD Rea et al., 2010). The more populated the place, the higher the likelihood of the occurrence of an emergency cardiac arrest (E Marijon et al., 2015). This insight suggests that the effectiveness of AEDs could be increased if concentration can be accurately measured.

In sum, the results show that the spatial distribution of public AEDs was only correlated with residential population density. They further indicate that, if cardiac arrest occurs during working hours, the current placement of AEDs is rather ineffective for the provision of first aid. However, additional information about where heart attacks are most likely to occur— home or work—is needed in order to draw a more comprehensive conclusion.

To enhance the effectiveness of public AEDs, analysis of various data is needed: worker density, business density, and de facto density. These data should be considered together when determining the location of public AEDs.

** Reference

Marijon, E., Bougouin, W., Tafflet, M., Karam, N., Jost, D., Lamhaut, L., … & Tourtier, J. P. (2015). Population movement and sudden cardiac arrest location. Circulation131(18), 1546-1554.

Rea, T. D., Olsufka, M., Bemis, B., White, L., Yin, L., Becker, L., … & Cobb, L. (2010). A population-based investigation of public access defibrillation: role of emergency medical services care. Resuscitation81(2), 163-167.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: