The Effect of Climatic Factors on the Provocation of Epileptic Seizures

Analyzing potential triggers of epileptic seizures is of great clinical relevance, since avoiding such triggers can prevent epileptic seizures. Possible triggers in special epileptic syndromes are, for example, psychological stress, sleep deprivation, sensory stimulation, forgetting to take medication, alcohol withdrawal, or hyperventilation.

This study aims to investigate the effect of climatic factors on the frequency of seizures, which is of special relevance in view of the general climate change.

Methods

Our exploratory retrospective study included anonymized data from all patients who were treated after an epileptic seizure in the Clinic for Neurology at the Westpfalz-Klinikum in Kaiserslautern in the time period from 1 January 2015 to 31 December 2019. Elective hospital admission for the diagnostic evaluation of epilepsy took place only in very few individual cases. The study population was divided into three age groups: the total population, those younger than 16 years, and those older than 16 years.

We considered 13 different climate parameters that Germany‘s National Meteorological Service made available: peak, mean, and lowest daily temperatures at 2 meters above ground (°C), daily means/averages of relative humidity (%), lowest temperatures at 5 cm above ground (°C), daily precipitation volumes (L/m²), average vapor pressure (hectopascal [hPa]), daily mean barometric pressure at the meteorological station Weinbiet (station) and in Kaiserslautern (hospital), duration of sunshine (measured as tenths of an hour), daily mean wind intensity/force (Beaufort), daily mean complete cloud cover (measured in eights), and maximum wind speed (m/s).

We used the Kruskal-Wallis test to analyze the frequency of seizures. We used Spearman’s correlation analysis and conditional Poisson regression for the statistical analysis of the association of climate parameters and frequency of seizures (1), with the seizure frequency modelled by applying one parameter in every case while adjusting for year, month, and day of the week. A delayed effect of the weather was analyzed by using models that applied the climate parameter with a lag of 1–3 days. We studied a linear association as well as a non-monotonical association; the parameters were classified into 3–5 categories on the basis of the respective quartiles.

Results

A total of 2813 epileptic seizures were analyzed for the five-year period. Of these, 2174 were in inpatients and 639 in outpatients. Patients who had several seizures were counted only once. This translates into a mean of 1.54 seizures per day. The gender distribution of the inpatient seizures was balanced, with 50.1% in women and 49.9% in men (Table 1).

Table 1

Mean daily seizure frequencies per month in the total study population, in those <16 years, and in those = 16 years

When analyzing the seizure frequency by month, the total population experienced the highest number—namely, 1.66 seizures per day in the month of October. The lowest number was seen in September, namely, 1.37 seizures per day. The Kruskal-Wallis test did not, however, show any statistically significant differences (total p=0.550; <16 years: p=0.904; ≥= 16 years: p=0.689) (Table 2).

Table 2

Correlations between climate parameters and seizure frequencies as well as incidence rate ratios (IRR) of the linear effects of climatic parameters resulting from the conditional Poisson models

Correlation analysis did not show significant associations between climate parameters and frequency of seizures. A wind speed of 7.7–9.4 m/s seems to have a protective effect compared with a wind speed <6.2 m/s (incidence rate ratio [IRR]=0.802; 95% confidence interval: [0.699; 0.920]; p = 0.002), whereas greater wind intensity two days previously tended to increase the risk of a seizure (IRR=1.066 [1.002; 1.134]; p = 0.044). The analyses of the 1–3 day lag did not find any significant abnormalities either.

Discussion

The effect of climatic factors on the probability/likelihood of developing an epileptic seizure is complex and not sufficiently understood (2, 3, 4). A delayed effect of climatic conditions on epileptic events is conceivable, which in our investigations is reflected in an increased seizure risk after a greater wind speed two days previously. The contradictory results of earlier studies can partly be explained with the fact that false-positive results and different climatic zones as can occur after multiple tests were not considered to a sufficient extent. This would also provide an explanation of why in Greece, greater numbers of seizures occurred during the summer season.

In sum, our data and those of comparable studies indicate that the effect of climatic factors and therefore climate change on epileptic seizures is small. Statistically reproducible results that cannot also be explained with the multiple testing problem, were not identified in our study nor in earlier comparable work. This may also be because modern human beings dwell primarily in protected air-conditioned rooms or vehicles. For people who are exposed to all weathers without protection—for example, farmers or roadworkers—a clinically relevant effect of certain climatic factors is certainly conceivable. This should be investigated in a more targeted fashion in future studies.

Epileptic seizures can unquestionably be provoked by trigger factors that place a strain on the organism. For this reason it may be assumed that extreme weather conditions can provoke seizures. In regions with a moderate climate, the unpleasantly cold winters are likely to have a small seizure provoking effect, whereas in the climate zones closer to the Equator, this is more likely for the hot summer months. Modern humans, however, mostly escape these strains and stresses. For a normal population, the effect of climatic factors is therefore rather small. For this reason, epilepsy patients should not be given any recommendation to restrict their lives/lifestyles unnecessarily.

Philipp Treib, Sebastian Treib, Werner Adler, Hajo Hamer, Stefan Schwab, Hermann Stefan, Thilo Hammen, Johannes Treib

Clinic for Neurology, University Hospital Erlangen (Treib P, Hamer, Schwab, Stefan, Hammen), [e-mail]

Polyclinic for Periodontology and Conservative Dentistry, University Medical Center Mainz (Treib P)

Clinic for Neurology, University Hospital Homburg (Treib S)

Institute for Medical Informatics, Biometry and Epidemiology, Friedrich-Alexander-University Erlangen (Adler)

Clinic for Neurology, Westpfalz-Klinikum Kaiserslautern (Hammen, Treib J)

Conflict of interest statement
The authors declare that no conflict of interest exists.

Manuscript received on 7 May 2021, revised version accepted on 11 August 2021.

Translated from the original German by Birte Twisselmann, PhD.

Cite this as:
Treib P, Treib S, Adler W, Hamer H, Schwab S, Stefan H, Hammen T, Treib J: The effect of climatic factors on the provocation of epileptic seizures. Dtsch Arztebl Int 2021; 118: 832–3. DOI: 10.3238/arztebl.m2021.0317

References

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