Send letter to journal:
Re: Effect of weather conditions on the mortality of heart attacks in Hungary

Dear Editor,

We read with great interest the very important article by Dilaveris et al about the climate impacts on myocardial infarction deaths in Athens, Greece [1]. Several reports have already proved that the number of deaths related to acute myocardial infarction (AMI) shows a seasonal variation, with a peak in winter, and a lowest number of mortality rates during the months of summer [2,3,4]. The effects of meteorological variables on the human organism have been studied for more than fifty years, and changes in the number of AMI events have been related to both cold or warm temperatures [5,6,7]. Some authors have found that the incidence of a hear attack may also be influenced by changes of atmospheric pressure and front movements [8,9].

Hungary is a small country in the middle of Europe, laying in the Carpathian basin. Based on our results it may be stated that the number of cardiac mortality (N=16.160) in Hungary shows a steadily decreasing tendency between 2000 and 2005, with a seasonal variation regardless of age or sex. Studying year 2001 in more detail, the peak period of AMI mortality was during the months of spring, with a lowest value during the summer. There was a significant difference between seasons (F=3.027; p<0.05; N=2850). The daily average of cardiovascular mortality during each season was the following: 8.48 during spring, 7.23 during the summer, 7.79 during autumn, and 7.76 during winter. The low rate of AMI mortality during the months of summer may be related to summer holidays in addition to favourable meteorological conditions. In addition to these findings, it seems that the changes of weather conditions also influence the mortality of other cardiovascular events. In Hungary the highest average daily temperature in year 2001 was 28.83 Celsius grade in the month of July, while the lowest average daily temperature was -10.93 Celsius grade in December.

With consideration to meteorological conditions, our results show, that the sharp temperature increase during spring, and the similarly significant decrease of temperatures during autumn, both have an increasing effect on heart attack related mortality. Studying the moving- average of AMI mortality (k=7), and the relation with the daily average temperature of the preceding 7 days, we have found a medium value negative correlation (r = -0.466, p<0.01).

Categorizing our data according to age groups, the strongest correlation was found in the age group of above 70 (r = -0.41, p<0.01), with a weaker relation in the age group between 50 and 70 (r = -0.315, p<0.01), while in the age group below 50 years of age, no correlation was found. Considering the moving average of deaths (k=7) and the average daily temperature of the preceding seven days above and below 20 Celsius grade, we have found a significant difference. When the average daily temperature of the preceding 7 days was above 20 Celsius grade, the average of daily mortality was 7.23, while below 20 Celsius grade the average of deaths was 7.93.

In the year 2001 in Hungary, the average daily atmospheric pressure showed its lowest seasonal average during spring (with a value of 1013.14 hPa), and the highest during autumn (1022.30 hPa). The moving average of deaths during spring (k=7) shows a weak negative correlation with average daily atmospheric pressure (r = -0.343, p<0.01). This finding suggests, that the mortality of acute myocardial infarction may be related to the internal biological rhythm of the organism, and also to such external conditions as weather. From a biometeorological point of view, the combined effect of certain meteorological factors, such as a sudden temperature or atmospheric pressure change, or the number of front movements, may be considered as a risk factor in the mortality of a heart attack. The more risk factors one bares, the higher the chance of developing a cardiovascular disease.

References

1. Dilaveris P, Synetos A, Giannopoulos G. et al.
Climate Impacts on Myocardial infarction deaths in the Athens Territory: the CLIMATE study.
Heart 2006;92:1747-51.

2. Gerber Y, Jacobsen SJ, Killian JM. et al.
Seasonality and daily weather conditions in relation to myocardial infarction and sudden cardiac death in Olmsted County, Minnesota, 1979 to 2002.
J Am Coll Cardiol 2006;48:287- 92.

3. Sayer JW, Wilkinson P, Ranjadayalan K, et al.
Attenuation or absence of circadian and seasonal rhythms of acute myocardial infarction.
Heart 1997;77:325-9.

4. Spencer FA, Goldberg RJ, Becker RC. et al.
Seasonal distribution of acute myocardial infarction in the second National Registry of Myocardial Infarction.
J Am Coll Cardiol 1998;3:1226-33.

5. Mestan JF, Kral V, Horni J.
Meteorological effects on myocardial infarct.
Cas Lek Cesk 1956;95:581-5.

6. Ku CS, Yang CY, Lee WJ. et al.
Absence of a seasonal variation in myocardial infarction onset in a region without temperature extremes.
Cardiology 1998;89:277-82.

7. Panagiotakos DB, Chrysohoou C, Pitsavos C. et al.
Climatological variations in daily hospital admissions for acute coronary syndromes.
Int J Cardiol 2004;94:229-33.

8. Houck PD, Lethen JE, Riggs MW. et al.
Relation of atmospheric pressure changes and the occurrences of acute myocardial infarction and stroke.
Am J Cardiol 2005;96:45-51.