In many European countries there is a tendency towards higher coronary mortality in the northern parts of the country. Furthermore the highest coronary mortality rates are found in the colder parts of Europe. We studied the regional variation in coronary mortality in the 284 Swedish municipalities during a ten-year period and the relation to the cold exposure in each municipality during the same time period.
Methods: Mortality rates for each municipality were acquired from the death certificates and indirectly standardised against the country. Temperature readings from measurements 5 times a day during daytime were used to form a cold index. We also compensated for wind chill by using Siples wind chill index. Multiple regression models were used. Second degree polynomials were used for the explanatory variables.
Results: There was a strong relation between the cold exposure in a municipality and coronary mortality. The cold index alone could explain 39% of the regional variation in coronary mortality. In a multiple regression model, cold index was the strongest explanatory variable. The coronary mortality in the coldest decile of the population was 40% higher than in the country as a whole.
Conclusions: There is a strong regional association between cold exposure and coronary mortality in Sweden. However, in this type of study, it is not possible to determine whether this association is a causal one or not.