Each panel shows coefficients from a county day–level multivariable linear regression in which the dependent variable was a specific weather outcome and independent variables included 20 lead day indicators, thunderstorm day indicator, and 20 lag day indicators (an event study approach). The lines represent different storm definitions (any lightning; lightning with positive precipitation, and lightning with positive precipitation and above-median wind speed on the storm date). All regressions adjusted for county, year, month of the year, and day of the week fixed effects. Full details are provided in the eMethods in the Supplement.
Each panel shows coefficients from a county day–level multivariable linear regression in which the dependent variable was the rate of emergency department visits for respiratory illness among Medicare beneficiaries (per million) and independent variables included 20 lead day indicators, thunderstorm day indicator, and 20 lag day indicators (an event study approach). Regressions were estimated separately for 4 groups of beneficiaries with different chronic condition histories. The lines represent different storm definitions (any lightning, lightning with positive precipitation, and lightning with positive precipitation and above-median wind speed on the storm date). All regressions adjusted for county, year, month of the year, and day of the week fixed effects. Full details are provided in the eMethods in the Supplement. COPD indicates chronic obstructive pulmonary disease.
eMethods. Weather Data Sources, Clinical Data Sources, Outcome Measures, and Statistical Analysis
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Zou E, Worsham C, Miller NH, Molitor D, Reif J, Jena AB. Emergency Visits for Thunderstorm-Related Respiratory Illnesses Among Older Adults. JAMA Intern Med. 2020;180(9):1248–1250. doi:10.1001/jamainternmed.2020.1672
Thunderstorm-related atmospheric changes are expected to increase in severity with rising global temperatures.1 Although large-scale evidence is limited, vulnerable populations, such as older adults or those with common chronic respiratory diseases, like asthma or chronic obstructive pulmonary disease (COPD), are expected to be susceptible to negative health effects from these changes.2 The objective of this study was to determine whether increases in emergency department (ED) visits for acute respiratory illnesses occur among Medicare beneficiaries in the days surrounding thunderstorms across the continental US.
We used publicly available atmospheric and lightning data from the US National Oceanic and Atmospheric Administration covering all 3127 counties in the continental US from January 1999 to December 2012. We combined this with insurance claims and comorbidity data from Medicare fee-for-service beneficiaries older than 65 years to identify all ED visits with acute respiratory diagnoses. The association between thunderstorm events, climatological and air pollutant changes, and respiratory ED visits was estimated using an event-study approach that focused on changes in environmental and health outcomes in the days before vs after a given thunderstorm event. Full details of the data sources, research methods, and statistical model design can be found in the eMethods in the Supplement. Analyses were performed in Stata (version 14; StataCorp). The 95% confidence interval around reported estimates reflects 0.025 in each tail or P ≤ .05. The study was approved by the institutional review board at the National Bureau of Economic Research and consent was waived because the study used deidentified observational data from Medicare claims.
Among 46 581 214 Medicare beneficiaries, the mean (SD) age was 77.0 (7.4) years; 26 710 591 (58.6%) were women; a chronic diagnosis of asthma was present for 4 891 027 (10.5%); 12 334 021 (26.5%) had COPD; and 3 074 360 (6.6%) had asthma and COPD. We identified 22 118 934 respiratory ED visits and 822 095 county days with major thunderstorms, defined by lightning, precipitation, and above-median wind speed.
Thunderstorms were associated with rises in temperature and particulate matter before the storm followed by declining levels on the day of and the days following the storm (Figure 1). Pollen counts and levels of nitrogen dioxide, ozone, sulfur dioxide, and carbon monoxide were unchanged until dropping after the storm. Above-baseline ED visits peaked the day before major storms, with a mean 1.8 additional visits per million beneficiaries overall (95% CI, 1.4-2.1), 6.3 for those with asthma (95% CI, 4.1-8.6), 6.4 for those with COPD (95% CI, 5.0-7.8), and 9.4 for those with asthma and COPD (95% CI, 6.2-12.7), corresponding to increases of 1.2%, 1.1%, 1.2%, and 1.2%, respectively (Figure 2). In the 3 or more days surrounding these storms, there were 5.3 (95% CI, 3.8-6.8) additional visits per million beneficiaries overall, 22.6 (95% CI, 16.0-29.2) for patients with asthma, 22.4 (95% CI, 17.4-27.4) for those with COPD, and 33.8 (95% CI, 24.0-43.6) for those with both. In a falsification analysis to assess for unmeasured confounders that could increase the likelihood of patients presenting to the ED before a major thunderstorm, we found no association between thunderstorms and ED visits for control conditions like sepsis or pulmonary embolism. Assuming an average 65 years or older population of 37.7 million Americans (based on census data), approximately 52 000 additional respiratory ED visits were estimated to occur in the 3 or more days surrounding major storms during the 14-year study period.
Emergency visits for acute respiratory illness significantly increased during the days before major thunderstorms among Medicare beneficiaries, particularly those with asthma and/or COPD. Visits were temporally associated with rises in temperature and particulate matter concentrations, atmospheric changes that have previously been associated with acute respiratory illness in the Medicare population.3,4
Rare epidemics of asthma following thunderstorms in other countries have been hypothesized to result from pollen grains rupturing when wet, allowing winds to carry small pollen particles that can trigger allergic asthma in susceptible patients.5 In this study, ED visits peaked before the thunderstorm, suggesting pollen particle release from precipitation was not the dominant mechanism. A limitation of this study is that it may not generalize to younger populations for which allergic asthma is common.6
To our knowledge, this is the first large-scale study to evaluate the association between thunderstorms and emergency visits for respiratory illness. Our findings suggest antecedent rises in particulate matter concentration and temperature may be the dominant mechanism of thunderstorm-associated acute respiratory disease in older Americans, which may contribute to strain on the health care system as storm activity increases with rising global temperatures
Accepted for Publication: April 6, 2020.
Corresponding Author: Anupam B. Jena, MD, PhD, Department of Health Care Policy, Harvard Medical School, 180 Longwood Ave, Boston, MA 02115 (firstname.lastname@example.org).
Published Online: August 10, 2020. doi:10.1001/jamainternmed.2020.1672
Author Contributions: Dr Zou had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Zou, Worsham, Miller, Molitor, Jena.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Zou, Worsham, Miller, Jena.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Zou, Worsham, Molitor, Jena.
Obtained funding: Miller, Molitor, Reif, Jena.
Administrative, technical, or material support: Miller, Molitor, Reif, Jena.
Supervision: Miller, Jena.
Conflict of Interest Disclosure: Dr Jena reports receiving consulting fees unrelated to this work from Pfizer, Hill Rom Services, Bristol Myers Squibb, Novartis, Amgen, Eli Lilly, Vertex Pharmaceuticals, AstraZeneca, Celgene, Tesaro, Sanofi Aventis, Biogen, Precision Health Economics, and Analysis Group.
Funding/Support: Support was provided by the Office of the Director, National Institutes of Health (grant 1DP5OD017897 to Dr Jena; R01AG053350 to Drs Miller, Molitor, and Reif).
Role of the Funder/Sponsor: The National Institutes of Health had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.