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ISDS 2012 Conference Abstracts

Evaluating Utility of Cold-Injury Syndromic Surveillance
Data in New York City
Kathryn Lane*1, Ramona Lall2, Katherine Wheeler1, Kazuhiko Ito1 and Thomas Matte1

1Bureau of Environmental Surveillance & Policy, NYC Department of Health & Mental Hygiene, New York, NY, USA; 2NYC Department
of Health & Mental Hygiene - Bureau of Communicable Diseases, New York, NY, USA

Objective
1) Develop cold exposure-related injury syndromic case defini-

tions 2) use historical data to compare trends among cases identified
in syndromic surveillance and cases identified in NY Statewide Plan-
ning and Research Cooperative System (SPARCS) hospital discharge
data to evaluate representativeness and 3) develop regression models
to examine relationships with cold weather conditions, and compare
relationships across case definitions and data sources.

Introduction
Cold weather exposure-related injuries range from hypothermia to

less severe conditions such as frost bite, trench foot, and chilblains,
which are all preventable causes of mortality and morbidity. In re-
cent years, NYC has successfully used syndromic surveillance of
heat-related ED visits to inform emergency response during heat
waves. Similar timely surveillance of cold-exposure related injuries
could also inform public health protection measures during severe
winter weather or cold season power outages. We conducted a retro-
spective analysis to compare hypothermia and cold-injury patient
case characteristics, as well as temporal and meteorological corre-
lates, between syndromic surveillance data and hospital discharge
data.

Methods
Using chief complaint key words, we developed syndromic case

definitions for 1) hypothermia only and 2) all injury caused by envi-
ronmental cold exposure. Case definitions were applied to an archive
of 2008-2010 cold season (October to April) syndromic surveillance
data reported from a subset of NYC emergency departments (ED SS),
representing 95% of all ED visits in NYC. Relevant ICD-9 codes
(991, E901.0, E901.8, E901.9, E988.3) were applied to ED discharge
data (ED Dx) to detect hypothermia and cold injury cases. Age, gen-
der, and alcohol involvement were compared using tests of proportion
to determine whether characteristics of cases identified through ED
SS were representative of cases identified in ED Dx data. Poisson re-
gression models were fit to estimate the relation of daily ED SS and
Dx counts with daily temperature, snow depth, and other weather
conditions. Models were adjusted for month, holiday, day of week,
and year to account for potential temporal confounding.

Results
Fewer hypothermia and cold injury cases were detected with ED

SS than with ED Dx but the two populations did not differ signifi-
cantly with respect to age and sex. From 2008-2010, there were 292
hypothermia cases with an average annual rate of 1.2 per 100,000
people, and 445 cold injury cases (1.8 per 100,000) identified in ED
SS data. Over the same time period, there were 566 hypothermia
cases (2.3 per 100,000) and 933 cold injury cases (3.7 per 100,000)
identified in ED Dx data. Daily counts of hypothermia and cold in-
jury were correlated across data sources. In preliminary analyses
using both case definitions, minimum daily temperature was associ-
ated with increases in daily ED SS and ED Dx counts. Mean daily
snow depth was associated with ED SS and ED Dx cold injury cases,
although not with hypothermia counts. Risk increased at lower tem-
peratures for both case definitions.

Conclusions
There were no meaningful differences between ED SS and ED Dx

weather models. Minimum temperature is associated with both case
definitions. Snow depth is associated with cold injury. Daily mini-
mum temperature and mean snow depth are potentially useful in de-
termining timing of surveillance. Syndromic surveillance data are a
timely means for monitoring hypothermia and other cold-related in-
juries, and could provide health departments with useful information
during severe winter weather to guide prevention.

Keywords
syndromic; cold-injury; environmental surveillance

Acknowledgments

Data Analysis and Syndromic Surveillance Unit, Bureau of Communica-
ble Diseases, NYC DOHMH

*Kathryn Lane
E-mail: klane1@health.nyc.gov

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e122, 2013