gms | German Medical Science

Objective: Frequency of aneurysmal subarachnoid hemorrhages (aSAH) presents complex fluctuations. This long-term retrospective study analyzes the possible seasonal and circaseptan influences as well as the relation with short-term weather changes.

Method: Bleeding dates and basic demographic data for all consecutive patients (n = 821) admitted to our vascular center for treatment of aSAH between January 2003 and December 2013 were collected from our continuously maintained database. Hourly meteorological data of the local weather station was retrieved from Germany's National Meteorological Service for the same time period. Measurements included air pressure, vapor pressure, air temperature, precipitation, wind speed, cloud cover and cumulated sunshine duration. Poisson regression was applied to assess short-term weather influence on aSAH frequency. Seasonal and circaseptan fluctuations were analyzed by Monte Carlo simulations (1,000,000 permutations). Statistical analysis was carried out with the STATA software package (Stata/MP 14.1 for Linux 64-bit).

Results: The study group comprised 274 (33.4%) male and 547 (66.6%) female patients (p < 0.001) with an average age of 54.3 years (standard error of the mean 0.47, range 13 -89). Days with preceding 5-day mean temperature (MT) below 0° Celsius had a significantly higher rate of aSAH (p < 0.001) than expected and days with MT above 22° Celsius had a significant lower rate of aSAH (p < 0.001) than expected. Poission regression did not reveal any further significant correlations between short-term meteorological fluctuations and frequency of aSHA. Seasonal fluctuations of aSAH with higher frequencies in winter have previously been published and were confirmed by our data: April (n = 58, p = 0.0983), August (n = 57, p = 0.0446) and December (n = 87, p = 0.015). Distinct circaseptan fluctuations were found in the data: lowest frequency on Wednesdays with 92 events (p = 0.0038) and highest frequency on Sundays with 131 events (p = 0.081). These fluctuations are supposedly associated with human behavior and particular habits and are only indirectly correlated with weather changes.

Conclusions: Short-term weather fluctuations only marginally influence the occurrence of aSAH. Differences of aSAH frequencies in extreme temperatures (below 5th and above 95th percentile) and circaseptan fluctuations are supposedly associated with human behavior and particular habits and not directly correlated with weather changes.