Cold Climate is an Important Factor in Explaining Regional Differences in Coronary Mortality Even if Serum Cholesterol and other Established Risk Factors are Taken into Account

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Abstract
Earlier studies have shown a strong regional association between cold climate and coronary mortality in Sweden and that coronary mortality is more strongly associated with cold climate than with other explanatory factors such as drinking water hardness, socioeconomic factors, tobacco and sales of butter. To examine the joint impact of these factors and to investigate regional differences in serum cholesterol and their relation to cold climate and coronary mortality, regression analyses were performed with 259 municipalities in Sweden as units. Mortality from acute myocardial infarction in men aged 40–64 during 1975–1984 was used as the dependent variable. A cold index was calculated, this index and the above mentioned factors were used as explanatory variables. The main results were: Cold index was the strongest factor when introduced into a multiple regression model. Four other strong factors had to be used to obtain the same explanatory strength as cold index did alone, and even when introduced as the last factor, cold index increased the coefficient of determination substantially. In a subsample of 37 municipalities, serum cholesterol was not significantly associated with coronary mortality. However, there was a significant correlation between cold index and serum cholesterol.