Virginia Thornley, M.D., Neurologist, Epileptologist
June 3, 2018
It is not common for a patient to complain of seizures seeming to increase immediately before a hurricane or a big storm. Do these changes truly correlate with outside environmental factors? This article seeks to review the literature to determine the cause and mechanisms of how weather risk factors might affect epilepsy and frequency of seizures. There is a paucity of information of barometric effects and weather changes on exacerbation of seizure frequency.
Changes in atmospheric pressure correlated with seizures
In one article studying 191 patients, with an increase in atmospheric pressure variability, seizures were noted to increase. The atmospheric pressure was obtained from metropolitan weather stations in Seattle. The maximum, minimum and changes were correlated with the number of seizures being monitored in a telemetry unit over 2005-2006. Patients with known epilepsy had an odds ratio of 2.6 (p=0.02) if the atmospheric pressure varied over 5.5mBar (1).
Higher temperatures correlated with more febrile seizures
In another study of 108,628 pediatric patients from January 2005-December, 2015 were studied regarding the effect of barometric pressure on the frequency of seizures. They were classified as febrile seizures, afebrile, epilepsy or status epilepticus. 53% presented as febrile seizures while 5.9% presented as status epilepticus. Mean atmospheric pressure was 1015.5hPa over the 11 year period. The mean temperature was 14.7 degrees Celsius with a variation of 8.3 degrees Celsius throughout the day. The study demonstrated febrile seizures were influenced by the temperature. At lower temperatures, the emergency room visits were less while at higher temperatures the visits increased (2).
Low barometric pressure, high air humidity increases seizures, high ambient temperature improved seizures
In another study where temperature, barometric pressure, and humidity were correlated with seizure frequency, 604 patients were studied between 2006-2010. The study showed that with a 10.7hPa lower atmospheric pressure there was an increase in seizures by 14%. Those with less severe seizures had an increase of 36%. Relative humidity of >80% correlated with increased seizures of 48%. A high ambient temperature of more than 20 degrees Celsius reduced seizures by 46% (4).
Cold temperature worsen seizures
In a study of 30 patients ages (19-54), patients with epilepsy appeared to have more active seizures during the seasons of spring, autumn and winter and less during summer of about 7%. During stable weather, it was 43% patients and unstable weather 63% had seizures. EEG’s changes occurred more frequently during winter. During winter seizures increased by 40%, in spring it increased 40% and spring by 43.3% (3).
While anecdotally, there is a correlation of exacerbation of seizure frequency to weather changes, the literature shows mixed results and some of them are small in number. One study showed a correlation of changes of more than 5.5mBar in barometric pressure leading to increased seizures frequency, another showed that it is the reduction in the atmospheric pressure itself that increased seizures. 1 study showed that high humidity may increase seizures. 2 studies showed that cold temperatures worsened seizures, while 1 study showed that higher ambient temperature worsened febrile seizures.
The data that was demonstrated is not uniform in the acquisition of information and there is a large variety of conditions. One study was primarily taken from ER visits another was information from inpatient video EEG monitoring units where the subset of patients may be completely different. In addition, there is a wide heterogeneity in etiologies of seizures which comes into play. Regardless, patients know their own symptoms, usually, if something is noted to trigger an event is it probably real.
- Doherty, et al, “Atmospheric pressure and seizure frequency in the epileptic unit: preliminary observations,” Epilepsia, 2007, Sep., 48 (9):1764-1767.
- Kim, et al, “The effects of weather on pediatric seizure; a single -center retrospective study,” Sci. Total Environ. , 2017, Dec., (609):535-540.
- Motta, et al, “Seizure frequency and bioelectric brain activity in epileptic patients in stable and unstable atmospheric pressure and temperature in different seasons of the year–a preliminary report,” Neurol. Neurochir. Pol, 2011, Nov.-Dec., 45(6):561-566.
- Rakers, et al, “Weather as a risk: a case-crossover study,” Epilepsia, 2017, Jul., 58(7): 1297-95.