Impact of weather and climate on the incidence of acute coronary syndromes

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Abstract

Background

First investigations of the interactions between weather and the incidence of acute myocardial infarctions date back to 1938[1]. The early observation of a higher incidence of myocardial infarctions in the cold season could be confirmed in very different geographical regions and cohorts. While the influence of seasonal variations on the incidence of myocardial infarctions has been extensively documented, the impact of individual meteorological parameters on the disease has so far not been investigated systematically. Hence the present study intended to assess the impact of the essential variables of weather and climate on the incidence of myocardial infarctions.

Methods

The daily incidence of myocardial infarctions was calculated from a national hospitalization survey. The hourly weather and climate data were provided by the database of the national weather forecast. The epidemiological and meteorological data were correlated by multivariate analysis based on a generalized linear model assuming a log-link-function and a Poisson distribution.

Results

High ambient pressure, high pressure gradients, and heavy wind activity were associated with an increase in the incidence of the totally 6560 hospitalizations for myocardial infarction irrespective of the geographical region. Snow- and rainfall had inconsistent effects. Temperature, Foehn, and lightning showed no statistically significant impact.

Conclusions

Ambient pressure, pressure gradient, and wind activity had a statistical impact on the incidence of myocardial infarctions in Switzerland from 1990 to 1994. To establish a cause-and-effect relationship more data are needed on the interaction between the pathophysiological mechanisms of the acute coronary syndrome and weather and climate variables.

Introduction

First investigations of the interactions between weather and the incidence of acute myocardial infarctions date back to 1938 [1]. The early observation of a higher incidence of myocardial infarctions in the cold season could be confirmed in very different geographical regions and cohorts in Germany (Berlin) [2], Italy (Milano) [3], Canada (Montreal) [4], Switzerland [5], [6], [7], USA (New England, South) [8] and Australia (Brisbane and New South Wales) [9], [10]. The Eurowinter-Study [11] demonstrated that a reduction in ambient temperature of as little as one degree Celsius was associated with an increase in myocardial infarction rates which could not be attributed to the classical risk factors alone [12], [13]. In addition case-reports indicated a trend towards higher infarction rates in extremely hot or cold climates [14], [15]. While the influence of seasonal variations on the incidence of myocardial infarctions has been extensively documented, the impact of individual meteorological parameters on the disease has so far not been investigated systematically. Switzerland suits well to investigate this question thanks to a national survey of diagnoses leading to hospitalizations, a dense, nationwide coverage with weather stations recording a series of meteorological variables, and finally the presence of several very different geographical regions such as the Alpine area with a harsh mountain climate, southern parts with subtropical characteristics, and the Swiss Plateau and Jura both with a more equilibrated meteorological pattern. These marked regional meteorological differences without significant demographic variations in terms of lifestyle, housing, or education allowed a comparison of myocardial infarction rates under different meteorological conditions.

Section snippets

Registry of myocardial infarction rates

The statistical tool to register the rates of myocardial infarctions was the Swiss Hospital Association VESKA database, a third-party-payer-imposed national survey of hospitalizations encompassing the majority of Swiss hospitals. The attending physician codes the diagnosis responsible for the current hospital admission indicating the day of admission. Because the coding takes place after hospital discharge the diagnosis of myocardial infarction was based on ECG- and enzyme criteria including

Statistical analysis

The hospitalizations for myocardial infarctions were reported daily but the meteorological parameters hourly. Therefore, the data of the 9 meteorological parameters were converted to daily mean values with the classification parameters already given as daily means. Consequently we performed multivariate analysis of 11 hospitals selected according to their situation in typical geographical regions and close to a weather station (Table 2). Meteorological variables which turned out to be

Results

In a four year period from 1990 to 1994 a total of 6560 patients (81% male, 19% female) were hospitalized for an acute myocardial infarction in 11 selected hospitals. The mean incidence (1990–1994) in July was 99 (84–112) compared to 145 (138–151) in January, the difference being statistically significant (p = 0.002). The annual mean decreased from 1507 in 1990 to 1124 in 1994. High ambient pressure (estimate 0.023, error 0.052) and its gradient (0.057, error 0.038) as well as high wind speed

Discussion

The hourly results of a total of 24 weather and climate variables were correlated with the daily hospitalization rates for acute myocardial infarction in three time windows (24, 48, and 144 h) in Switzerland from 1990 to 1994. A multivariate analysis yielded consistent positive correlations for absolute ambient pressure, pressure gradient, and wind speed (Fig. 1). In a clinical setting this observation means that on days with high absolute pressure or rapid increase in ambient pressure or heavy

Conclusion

Ambient pressure, pressure gradient, and wind activity had a statistical impact on the incidence of myocardial infarctions in Switzerland from 1990 to 1994. To establish a cause-and-effect relationship more data are needed on the interaction between the pathophysiological mechanisms of the acute coronary syndrome and weather and climate variables.

Acknowledgement

We thank Hans Ehrensberger for his kind advice and support concerning the Swiss hospital database VESKA.

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  • Cited by (0)

    1

    Cardiologist, Kantonsspital Olten, Switzerland.

    2

    Institute for Social and Preventive Medicine, University of Bern, Switzerland.

    3

    Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland.

    4

    Head of Division of Biometeorology, MeteoSchweiz, Zurich, Switzerland.

    5

    Associate Professor and Head of Institute for Social and Preventive Medicine, University of Bern, Switzerland.

    6

    Professor and Head of Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland.

    7

    Professor and Head of Cardiology, Swiss Cardiovascular Center Bern, University Hospital, Bern, Switzerland.

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