Role of El Niño Southern Oscillation (ENSO) in Extreme Event Related Adverse Health Outcomes in Maryland, USA

Abstract

Introduction: Increasing body of literature suggests frequency, duration, and intensity of extreme events are rising and will increase in response to changing climate. Others have linked such extreme events with adverse health outcomes. Large-scale weather phenomenon (i.e., ENSO) is known to impact US weather patterns, but no studies to date have investigated how ENSO may modulate the associations between extreme events and adverse health outcomes. Methods: We linked hospitalization records for asthma/MI and culture-confirmed campylobacter/salmonella infections with extreme heat and precipitation events in Maryland. Extreme events were identified based on local climatology specific to each county derived from a 30-year baseline. We obtained data on phases of ENSO (El Niño, La Niña, Neutral) from the National Weather Service Climate Prediction Center. A time-stratified case-crossover design was used to examine associations between exposure to extreme events exposure and chronic health outcomes, while infection risk was assessed using multivariate negative binomial regression. We used stratified analysis to investigate how associations varied by ENSO phase. Results: There were 116,470 asthma and 138,343 MI hospitalizations and 4,804 and 9,527 reported infections of campylobacter and salmonella, respectively, during the study periods. Risk of salmonella and campylobacter associated with extreme heat and precipitation events was highest during the La Niña period. For asthma, risk associated with extreme heat and precipitation events was highest during El Niño. For MI, extreme heat related risk was highest during El Niño, while extreme precipitation related risk was highest during La Niña. Conclusion: Our results show extreme heat and precipitation related risk varies considerably during ENSO phases, which has a strong but uneven influence on weather across the globe. Studies investigating the link between climate change and health need to account for this phenomenon.