Background/Purpose: To examine the influence of solar cycle and geomagnetic effects on SLE disease activity.

Methods: The data used for the analysis consisted of 327 observations of 27-day Physician Global Assessment (PGA) averages of patients with SLE seen in the Hopkins Lupus Center from 1996-2020. The considered geomagnetic indices were the AP index (geomagnetic activity), sunspot number index R (area of solar surface covered by spots), the F10.7 index (noise level generated by the sun at a wavelength of 10.7 cm at the earth’s orbit), the AU index (upper auroral electrojet index), and high energy ( > 60 Mev) proton flux events. Geomagnetic data were obtained from the Goddard Space Flight Center Space Physics Data Facility. A time series decomposition of the PGA averages was performed as the first step.  The linear relationships between the PGA and the geomagnetic indices were examined using parametric statistical methods such as Pearson’s correlation and linear regression, while the nonlinear relationships were examined using nonparametric statistical methods such as Spearman’s rho and Kernel regression.

Results: After time series deconstruction of PGA averages, the seasonality explained a significant fraction of the variance of the time series (R² =38.7%) with one cycle completed every 16 years. Increases in the number of high energy proton fluxes were associated with decreases in the PGA (p< 0.05). Increases in sunspot number index R anticipated decreases in the PGA (p< 0.05). Increases in the Ap index were associated with decreases in the PGA (p< 0.1).

Conclusion: The seasonality of the PGA averages (one cycle every 16 years) explains a significant fraction of the variance of the time series. Geomagnetic disturbances, including the level of geomagnetic activity, sunspot numbers, and high proton flux events may explain part of the described seasonality seen in SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/systemic-lupus-erythematosus-and-geomagnetic-disturbances-a-time-series-analysis/