ED visits were by Non-Hispanic Black patients, 37% by non-Hispanic White patients,
3% by Hispanic or Latino patients, and the remaining 6% by patients of other racial and
ethnic groups. Describing ED visit payment methods, 11% of patient visits were covered by
Medicare, 42% by Medicaid, 22% by private insurance, and 22% were self-paid.
Following Hurricane Irene, 38 of 100 counties in North Carolina had disaster declarations,
mostly along the eastern coast and counties adjacent to the coastal counties (Figure 1).
Examining asthma-related ED visit rates across all counties in North Carolina, in September
2010 the asthma-related ED visit rate was 6 per 10,000 person months. This is compared
with September 2011, following Hurricane Irene, when rates of asthma-related ED visits
were similar in counties with and without disaster declarations (7 per 10,000 person months
and 5 per 10,000 person months, respectively) (Table 1). In difference of differences
analyses, rates of asthma ED visits counties affected differed little, if at all, from rates
in counties not affected by the hurricane (rate ratio [95% confidence interval]=1.02 [0.97,
1.08]) when adjusting for county, month, and year and accounting for correlation between
monthly-county rates within the same year. In sensitivity analyses using rainfall levels
instead of disaster declaration as the exposure metric, there was little or no difference in
the rate of asthma ED visits between counties that experienced >7 inches of rain and 2–7
inches of rain compared to those that had ≤2 inches of rain following Hurricane Irene (RR
[95% CI]=0.93 [0.85, 1.02] and 1.01 [0.95, 1.09] respectively) when controlling for the
same factors as in the primary model.
DISCUSSION
In this study, we examined changes in county-level ED visits for asthma in North Carolina
following Hurricane Irene. Although asthma triggers introduced following hurricanes can
increase asthma exacerbations, we observed little evidence of a change in asthma ED visits
following Hurricane Irene. There are several potential explanations for these results. It
is possible that aggregating visits by county masked a true association between hurricane-
related exposures and asthma exacerbations. A more granular level of exposure, for example
an individual-level estimate of home flooding or displacement, may have been better suited
to identify potential impacts of Hurricane Irene on patients with asthma. Alternatively, it is
possible that there was no impact of Hurricane Irene on asthma in North Carolina. Another
study found an impact from hurricanes on people with asthma examined the effects of
Hurricane Katrina [2]. Hurricane Katrina was a category 5 hurricane when it made landfall
and had a higher economic and infrastructural impact on the New Orleans community
than Hurricane Irene had on North Carolina. It is possible that hurricane Katrina, a larger
magnitude storm with those greater impacts, had more effects on patients with asthma.
Additionally, there may have been more knowledge of how to control asthma following
a storm among the people impacted by Hurricane Irene than those living in New Orleans
during Hurricane Katrina.
A strength of this study was the use of HCUP data which captured >97% of ED visits
in North Carolina for the months included in this analysis. Another strength of this study
is the use of FEMA disaster declarations as a proxy for hurricane impact. Using FEMA
disaster declarations helped capture all effects of Hurricane Irene such as flooding, home
Cowan et al.
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Disaster Med Public Health Prep
. Author manuscript; available in PMC 2022 December 21.
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