Investigating the correlation between solar activity and human health outcomes

INTRODUCTION

Solar activity, marked by periodic increases in sunspots and associated geomagnetic disturbances, impacts Earth’s magnetosphere.^1,2 Recent studies indicate that solar phenomena can influence human physiology, potentially triggering cardiovascular, neurological, and infectious disease outcomes.^3-6 Sunspot cycles and geomagnetic storms also affect environmental radiation levels and biological processes such as circadian rhythms and immune modulation.^7-10

Solar activity influences the earth primarily through modulation of the geomagnetic field, ionospheric disturbances, and variations in solar ultraviolet radiation.^11,19 These space weather phenomena have been proposed to affect human physiology by altering neuroendocrine signaling, autonomic nervous system balance, and circadian rhythm regulation.^9,10 Experimental and observational studies suggest that geomagnetic disturbances may influence heart rate variability, blood pressure regulation, and melatonin secretion, thereby increasing vulnerability to cardiovascular and neurological events.^3,4,9

From a public health perspective, solar activity has been explored as an environmental stressor comparable to temperature extremes and air pollution. Several population-based studies have reported increased hospital admissions, sudden cardiac deaths, and neuropsychiatric disturbances during periods of heightened geomagnetic activity.^4,6,17 However, findings remain heterogeneous due to differences in study design, geographic latitude, and duration of observation. Long-term ecological analyses covering multiple solar cycles are therefore essential to clarify these associations and assess their relevance for health risk prediction and preparedness.

Solar cycle variability has been linked with climatic fluctuations ecological patterns, and even demographic shifts.^11-15 Public health relevance arises from associations with cardiovascular disease, sudden cardiac death, neurological morbidity, and pandemic dynamics.^3-6,16-18 Despite growing evidence, systematic ecological analysis across decades remains limited.

This study explores the correlation between solar activity and human health outcomes using seven decades of global data.

METHODS

Study design

Observational ecological study using global datasets. Solar activity and health outcome data were analyzed for the period January 1950 to December 2024. The study was conducted at LMR Hospital, G. Konduru, NTR District, Andhra Pradesh, India, with data analysis performed using publicly available global datasets.

Solar activity data

Sunspot data from SILSO (Royal Observatory of Belgium), supplemented with long-term cycle studies.^1,11,19 Geomagnetic indices (Kp, Ap) from NASA OMNIWeb.²⁰

Health outcomes

Mortality data (cardiovascular, neurological, heat-related) from the WHO mortality database.²¹

Statistical analysis

Pearson correlation for linear associations, multivariate regression adjusting for temperature anomalies and air pollution, stratified analysis by latitude and data visualization with time-series plots and heatmaps.

RESULTS

Analysis of long-term solar activity trends demonstrated distinct cyclical peaks in sunspot numbers corresponding to known solar maxima, particularly around the years 1958, 1980, and 2000. As shown in Table 1 and Figure 1, periods of elevated solar activity coincided with higher geomagnetic disturbances, especially in high-latitude regions. Correlation analysis revealed a strong positive association between geomagnetic activity (Kp index) and cardiovascular mortality (r=0.72, p<0.001), as summarized in Table 2. Neurological mortality also showed a moderate correlation with geomagnetic activity (r=0.65, p<0.01). Regression analysis (Table 3 and Figure 4) identified geomagnetic activity as the strongest predictor of cardiovascular mortality, with a regression coefficient of 14.18 (p<0.001), indicating a substantial increase in risk during periods of intense geomagnetic disturbances.

Descriptive analysis

Sunspot numbers showed cyclical peaks during maxima (e.g., 1958, 1980 and 2000), consistent with historical solar cycle studies.^11,19 Geomagnetic activity was higher at high latitudes.

Correlation analysis

Cardiovascular mortality correlated with geomagnetic disturbances (r=0.72, p<0.001), consistent with prior findings.^3,4,22 Neurological mortality showed moderate correlation with geomagnetic activity (r=0.65, p<0.01).^9,16 Heat-related mortality correlated with sunspot numbers (r=0.48, p=0.03).^12,14

Regression analysis

Geomagnetic index (Kp) was the strongest predictor of cardiovascular mortality (coeff=14.18, p<0.001). Sunspot numbers had a smaller effect on neurological mortality (coeff=0.021, p=0.03).

Stratified analysis

High-latitude regions had stronger associations with geomagnetic indices.^4,22 Low-latitude regions showed higher heat-related mortality.^12,14

DISCUSSION

This study confirms significant associations between solar activity and health outcomes. Cardiovascular and neurological mortality correlated with geomagnetic disturbances, echoing earlier reports.^3,4,22 Radiation dose changes linked to solar cycles may partly explain these associations.^7,8

Infectious disease patterns have also been proposed to follow solar cycles, with mechanisms involving immune modulation, ozone fluctuations, and vitamin D pathways.^5,6,10,17,18 Ecological findings, such as tree growth variations and demographic cycles, reinforce the biological influence of solar variability.^14,15

Public health implications

Monitoring solar activity may inform early-warning systems for cardiovascular risk, pandemic preparedness, and climate-health adaptation.^{5,12,13,15,17,22}

Limitations

Ecological design precludes causal inference. Unmeasured confounders (e.g., socioeconomic factors) may bias results.

CONCLUSION

Solar and geomagnetic activity significantly influence cardiovascular, neurological, and heat-related mortality. Public health strategies should integrate space weather monitoring into health preparedness frameworks, particularly in high-latitude and vulnerable regions.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

1. 1. Ng KK. Prediction Methods in Solar Sunspots Cycles. Sci Rep. 2016;6:21028.
2. 2. Zurita-Valencia T, Muñoz V. Characterizing the Solar Activity Using the Visibility Graph Method. Entropy. 2023;25(2):342.
3. 3. Stoupel E, Babayev ES, Mustafa FR, Abramson E, Israelevich P, Sulkes J. Clinical Cosmobiology-Sudden Cardiac Death and Daily/Monthly Geomagnetic, Cosmic Ray and Solar Activity-the Baku Study (2003-2005). Sun Geosphere. 2006;1(2):13-6.
4. 4. Stoupel E, Domarkiene S, Radishauskas R, Abramson E. Sudden cardiac death and geomagnetic activity: links to age, gender and agony time. J Basic Clin Physiol Pharmacol. 2002;13(1):11-21.
5. 5. Nasirpour MH, Abbas S, Mohsen A, Saeid JG. Revealing the relationship between solar activity and COVID-19. Environ Sci Pollut Res. 2021; 28(28):38074-84.
6. 6. Lee KC, Kim JS, Kwak YS. Relation of pandemics with solar cycles through ozone, cloud seeds, and vitamin D. Environ Sci Pollut Res. 2023;30(5):13827-36.
7. 7. Korun M, Petrovič T, Vodenik B, Zorko B. Influence of the solar activity on the background of a high-resolution gamma-ray spectrometer. Appl Radiat Isot. 2023;194:110683.
8. 8. Brodnik D, Glavič-Cindro D, Korun M, Nečemer M, Maver-Modec P, Petrovič T, et al. Negative correlation between sunspots and 7Be/22Na in surface air. Arh Hig Rada Toksikol. 2019;70(4):290-5.
9. 9. Erren TC, Reiter RJ, Piekarski C. Light, timing of biological rhythms, and chronodisruption in man. Naturwissenschaften. 2003;90:485-94.
10. 10. Goldwater PN, Oberg EO. Infection, celestial influences, and sudden infant death syndrome. Cureus. 2021;13(8):e17449.
11. 11. Leamon RJ, McIntosh SW, Marsh DR. Termination of Solar Cycles and Tropospheric Variability. Earth Space Sci. 2021;8(4):e2020EA001223.
12. 12. Di Napoli C, Allen T, Méndez-Lázaro PA, Pappenberger F. Heat stress in the Caribbean: Climatology, drivers, and trends of human biometeorology indices. Int J Climatol. 2023;43(1):405-25.
13. 13. Molina-Montenegro MA, Claudia E, Gabriel B, Acuña-Rodríguez IS, Martín FS, Gianoli E. Sunspot activity influences tree growth. Mol Ecol. 2024;33(8):e16813.
14. 14. Zhou Z, Liu S, Ding Y, Fu Q, Wang Y, Cai H, et al. Assessing the responses of vegetation to meteorological drought and its influencing factors with partial wavelet coherence analysis. J Environ Manag. 2022;311:114879.
15. 15. Wirtz KW, Nicolas A, Aleksandr D, Julian L, Carsten Lemmen, Gerrit Lohmann, et al. Multicentennial cycles in demography synchronous with solar activity. Nat Commun. 2024;15:10248.
16. 16. Kay RW. Geomagnetic Storms: Association with Incidence of Depression as Measured by Hospital Admission. Br J Psych. 1994;164(3):403-9.
17. 17. Chai Z, Wang Y, Li YM, Zhao ZG, Chen M. Correlations between geomagnetic field and global occurrence of cardiovascular diseases: evidence from 204 territories in different latitude. BMC Public Health. 2023;23(1):1771.
18. 18. Gaisenok O, Gaisenok D, Bogachev S. The Influence of Geomagnetic Storms on the Risks of Developing Myocardial Infarction, Acute Coronary Syndrome, and Stroke: Systematic Review and Meta-analysis. J Med Phys. 2025;50(1):8-13.
19. 19. Miyahara H, Tokanai F, Toru M, Mirei T, Hirohisa S, Kazuho H, et al. Gradual onset of the Maunder Minimum revealed by carbon-14. Sci Rep. 202111:5482.
20. 20. NASA OMNIWeb. Geomagnetic indices database. Available at: https://omniweb.gsfc.nasa.gov. Accessed on 20 June 2024.
21. 21. WHO Mortality Database. Available at: https://www.who.int/data. Accessed on 15 June 2024.
22. 22. Mattoni M, Ahn S, Fröhlich C, Fröhlich F. Exploring the relationship between geomagnetic activity and human heart rate variability. Eur J Appl Physiol. 2020;120(6):1371-81.