The research article, “Changes in Emergency Department Access Between 2001 and 2005
Among General and Vulnerable Populations” by Shen & Hsia analyzes how geographic access to
emergency departments changed between 2001 and 2005 among populations in over 28,000
neighborhoods among the general population while also looking at some vulnerable populations
including race/ethnicity, foreign-born individuals, and economically disadvantaged communities. They
assessed a baseline of how long it took from the center of each zip code to the nearest emergency
department and compared it with the changes in 2005 using stacked bar graphs. They found that “more
than 95% of the population had the same or improved geographic access to EDs between 2001 and 2005
(Shen & Hsia, 2010).” However, deteriorating access of 10 minutes or longer occurred mostly in
communities with economic proportions and high shares of non-white races, particularly Hispanics. This
is good news for much of the population, but in those communities, roughly 11.4 million people, have
increased driving times, particularly rural communities. In the case of major emergencies such as
strokes and heart attacks, mere minutes could mean the difference between life and death.
When showing the distribution of the changes in time between 2001 and 2005, the authors
used stacked bar graphs. They could have used pie charts and compared rural and urban communities.
I believe they chose stacked bar graphs, ultimately, because 95% of the populations did not have an
increase in driving time. This would have left a small sliver that would have been difficult to distinguish
between the less than 10 minutes group and the 10 minutes and more groups (Shen & Hsia, 2010). It
made more sense to use bar graphs, because it is easier to see the differences between those 2,
because as I stated before mere minutes make a big difference in emergent situations. Within this
article, the authors identified the relative risk ratio, also called relative risk or risk ratio within urban and
rural populations and among vulnerable populations. According to Sullivan, relative risk is defined as
“the ratio of prevalence or incidence in the exposed group to the prevalence or incidence in the
unexposed group (2012).” According to Shen and Hsia, the reference group, also known as the
unexposed group, in the case of low-income communities in urban areas, was those communities with
high-incomes within urban areas and the exposed group was the low-income communities within urban
areas (2010).
According to table 2 of the research done by Shen & Hsia, the relative risk ratio for communities
with a high share of foreign-born populations in rural areas was 0.70. The exposed population was
those communities with a high share of foreign-born populations in rural areas whose driving time to
EDs increased by at least 10 minutes. The unexposed population was those with a high share of foreignborn populations that saw no increase in driving time or the increase was less than 10 minutes (2010).
The relative risk ratio means that those communities with a high share of foreign-born populations in
rural areas had a decreased risk of an increase in driving time being 10 minutes or more.
References
Shen, Y. & Hsia, R.Y. (2010). Changes in Emergency Department access between 2001 and 2005 among
general and vulnerable populations. American Journal of Public Health. Vol 100, No. 8. Retrieved
May 13, 2013 from
https://engage.cune.edu/learn/pluginfile.php/7396/mod_forum/intro/Ch3EmergencyDepartme
nt.pdf
Sullivan, L. M. (2012). Essentials of Biostatistics in Public Health (2nd Ed.). Sudbury, MA: Jones and
Bartlett Learning.