The Influence of Meteorological Changes on Coronary Thrombosis

Abstract

The present study represents an analysis of all patients admitted to the Royal Victoria Hospital, Belfast, during the period 1953 to 1956 inclusive. The object was to determine the incidence and mortality in relation to sex, age, and the blood pressure on admission and in particular in relation to climatic factors. The influence of weather was especially studied, because of an impression that the admission rate varied with the time of year, a feature that has been reported previously (Teng and Heyer, 1955), but inadequately studied. METHODSThe records of all patients admitted as coronary thrombosis or myocardial infarction during the period 1953 to 1956 inclusive were reviewed and in addition meteorological data for the City of Belfast were obtained from the Meteorological Observatory of Queen's University of Belfast. In each case details of age, sex, blood pressure on admission, address, date of infarction, activity at the time of infarction, and ultimate fate were recorded. Where there was a history of more than one attack, only the details of the first were taken. There were in all 390 cases, but 30 of these were excluded, because they lived outside Belfast, where no meteorological information was available. In a further 62 cases the records were incomplete in one or more respects: these were excluded from the study apart from certain comparisons, for which data were available. In only 126 cases were the activities of the patients at the time of onset of myocardial infarction recorded.There is no reason to believe that the patients for whom data were incomplete differed in any way from the rest. Also, the system of admissions in the Belfast area would justify the assumption that the admissions of patients with coronary disease into the Royal Victoria Hospital are typical of those of all general hospitals in Belfast.Summary of Statistical Techniques. In this report the frequency of admissions of patients with coronary thrombosis has been examined in relation to age and sex, daily, monthly, and seasonal variations, and also in relation to the possible influences of meteorological changes. The immediate mortality of these cases has also been examined with regard to age and blood pressure on admission.Throughout this report these observed frequencies have been tested against frequencies expected by particular hypotheses by means of the x2 test. The hypotheses on which the expected values are calculated vary for the different variables given above. For example, the observed number of admissions on each day of the week was compared with that expected on the hypothesis that, if there was no variation with the day of the week, then admissions would be expected to occur with equal frequency (i.e. on any one day one-seventh of the total admissions). The expected values for monthly and seasonal distributions of admission were calculated on similar hypotheses. 635 group.bmj.com on June 23, 2015 -Published by http://heart.bmj.com/ Downloaded from

A Comparative Study of Myocardial Infarction and Cerebral Vascular Accidents

“…Figure 4 shows a clear relationship between season and the number of admissions with both myocardial infarction and cerebral vascular accidents. This has been reported previously [Adesola, 1960;Aring and M erritt, 1935].…”