The impact of geomagnetic disturbances on mortality from respiratory tract infections in the USA, 2000–2019

BACKGROUND: Respiratory tract infections (RTIs) are a major cause of mortality, particularly among older adults. While air pollution and climate variability are known contributors to RTI risk, the role of solar activity-related short-term geomagnetic disturbances (GMD), remains underexplored. OBJECTIVE: This study investigates the association between GMD, quantified using the 6-month moving average (MA) of the GMD index (Kp), and RTI-related monthly mortality in the United States between 2000 and 2019. METHODS: We analyzed monthly mortality data from 47 contiguous U.S. states using CDC records. RTI-related deaths were identified by ICD-10 codes, and Kp index was used as a GMD exposure metric. We applied generalized estimating equations (GEE) with Poisson regression to estimate relative risks (RRs) and attributable fractions (AFs), adjusting for county-level covariates. Analyses were stratified by sex, age, and U.S. Census regions. RESULTS: Among all exposure windows tested (1-12 months), the 6-month MA of the Kp index showed the strongest association. Statistically significant associations were observed in all age groups (65-74, 75-84, ≥85). The RRs per interquartile range (IQR) increase of Kp were 1.14, 1.12, and 1.16 for females, and 1.13, 1.11, and 1.14 for males, respectively. The highest risks were detected in the ≥85 age group: 1.16 (95% CI: 1.14-1.18) for females and 1.14 (95% CI: 1.12-1.16) for males. Geographic variability was also observed, with higher RRs in the West and Midwest regions, though not statistically significant. SIGNIFICANCE: This study provides the first large-scale evidence that GMD may be associated with increased RTI-related mortality in the U.S., particularly among older adults. IMPACT: The findings suggest that solar activity and space weather may influence human health through mechanisms such as immune modulation or circadian disruption. Recognizing GMD as a potential contributor to RTI mortality could inform early warning systems and preventive strategies, especially for vulnerable elderly populations.