Sferics and headache: a prospective study.

Sferics are low frequency, low intensity electromagnetic pulses radiating from distant meteorological events and other yet unknown sources. It has been hypothesized that sferics are part of the purported sensitivity to weather changes reported by headache sufferers. We tested this proposal. Patients (migraine and/or tension headache) enrolled in a randomized clinical trial gave daily headache data (intensity, frequency, duration of headache) for at least 18 weeks. Concurrently, a sferics measurement station in the vicinity of the patients recorded frequency and intensity of sferics. Usable headache data from 21 patients and the corresponding sferics series were subjected to time series analysis applying ARIMA models and then cross-correlated. We found significant and consistent cross-correlations of moderate size at lag 0 in one patient between ARIMA-filtered headache intensity and frequency (r = 0.18) and amplitude of sferics (r = 0.20). We conclude that in an unselected sample of headache patients some may indeed be susceptible to the low intensity type of electromagnetic radiation exemplified by sferics pulses. This phenomenon warrants further scrutiny.