Population Health and the Polar Vortex

This winter’s “polar vortex” has led to discussions about everything from the devastating effects sub-zero temperatures can have on homeless populations, to the difficulties it’s caused marathon runners in training, and the dangers extreme cold can pose to pets.

Here at HMS, we saw several state public health departments use EpiCenter to implement a cold weather classifier that would enable them to track the number of injuries related to the extreme cold. This tool allowed for the tracking and analysis of emergency department registrations with chief complaints containing phrases like “out in the cold,” “no heat,” “hypothermia,” “frostbite,” and “exposure.” Observing event-specific data in situations like these allows public health to track the overall health of the population, and also to monitor the effectiveness of public outreach efforts and public health warnings.

New Jersey used EpiCenter to create a cold-related injury classifier with input from HMS, which they utilized in conjunction with their Super Bowl surveillance. Ohio created their own, separate cold-related injury classifier in EpiCenter and then shared the SAS code for that classifier with the International Society for Disease Surveillance (ISDS). Several other regions, including Indiana, New Hampshire, Washington, and Boston, then implemented the same code in their own cold weather surveillance.

During the first round of severely cold temperatures on January 6th, 7th, and 8th, temperatures in Ohio dropped well below zero degrees Fahrenheit. As could be expected, they observed a surge in ED visits due to cold-related injuries, with visit numbers peaking on the 8th. After that initial cold snap, Ohio initiated public health messages warning the population about taking precautions to seek shelter and stay out of the cold. The second cold snap on January 28th and 29th, during which temperatures dropped even lower, yielded dramatically fewer emergency department visits, a trend that Ohio’s public health officials believe can be attributed in part to the warnings they issued following the initial burst of below-freezing temperatures.

Cold-Related Injury ED visits in Ohio

The availability of this sort of data is opening doors for research on the relationships between public policy measures and emergency department utilization. For example, January’s cold-related injury data could be leveraged in conjunction with information about the capacity of homeless shelters and auxiliary facilities to assess the effects of public policy on the numbers of emergency department visits. Several state public health departments have also created heat-related injury classifiers in preparation for summer; as this sort of data becomes more widely available via tools like EpiCenter, we look forward to seeing the new ways public health discovers to more effectively monitor and improve population health.