Mary E. Helander: 0000-0002-5185-6867

Margaret Formica: 0000-0003-4379-6718

Dessa Bergen-Cico: 0000-0002-8852-732X

Document Type





NEMSIS, 9-1-1, EMS, sinusoidal regression, population health, emergency medical events




Syracuse University, Lerner Center


This research was performed while the first author was funded as a Graduate Research Fellow in the Lerner Center for Public Health Promotion and Center for Policy Research, Maxwell School of Citizenship and Public Affairs, Syracuse University. Special thanks to Marita Begley for copy-editing and proofreading.


Data Science | Epidemiology | Public Health | Social and Behavioral Sciences


This study examines population level daily patterns of time-stamped emergency medical service (EMS) dispatches to establish their situational predictability. Using visualization, sinusoidal regression, and statistical tests to compare empirical cumulative distributions, we analyzed 311,848,450 emergency medical call records from the U.S. National Emergency Medical Services Information System (NEMSIS) for years 2010 through 2022. The analysis revealed a robust daily pattern in the hourly distribution of distress calls across 33 major categories of medical emergency dispatch types. Sinusoidal regression coefficients for all types were statistically significant, mostly at the p < 0.0001 level. The coefficient of determination ($R^2$) ranged from 0.84 and 0.99 for all models, with most falling in the 0.94 to 0.99 range. The common sinusoidal pattern, peaking in mid-afternoon, demonstrates that all major categories of medical emergency dispatch types appear to be influenced by an underlying daily rhythm that is aligned with daylight hours and common sleep/wake cycles. A comparison of results with previous landmark studies revealed new and contrasting EMS patterns for several long-established peak occurrence hours--specifically for chest pain, heart problems, stroke, convulsions and seizures, and sudden cardiac arrest/death. Upon closer examination, we also found that heart attacks, diagnosed by paramedics in the field via 12-lead cardiac monitoring, followed the identified common daily pattern of a mid-afternoon peak, departing from prior generally accepted morning tendencies. Extended analysis revealed that the normative pattern prevailed across the NEMSIS data when re-organized to consider monthly, seasonal, daylight-savings vs civil time, and pre-/post- COVID-19 periods. The predictable daily EMS patterns provide impetus for more research that links daily variation with causal risk and protective factors. Our methods are straightforward and presented with detail to provide accessible and replicable implementation for researchers and practitioners.

Additional Information

JOURNAL OF BIOLOGICAL RHYTHMS, Vol. XX No. X, Month 202X 1–21 DOI: 10.1177/07487304231193876

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.