The events registration and survey procedures in the Northern Sweden MONICA Project

Introduction: The WHO MONICA Project (Multinational Monitoring of Trends and Determinants in Cardiovascular Disease) was initiated in 1982. The purpose was to evaluate to what extent mortality trends could be explained by changes over time in the population load of conventional cardiovascular risk factors. To test this hypothesis, time trends in cardiovascular event rates have been correlated with trends in levels of risk factors in 35- to 64-year-old men and women in 38 populations. In most MONICA populations, the study has covered a period of 10 years or more. Methods: All acute myocardial infarction and stroke events have been registered in a population-based setting in Norrbotten and Vasterbotten counties from 1985 and onwards. The total population is approximately 510,000 inhabitants. In the frame of the WHO MONICA Project, the same strict criteria have been used in all years. Another part of the MONICA Project is population risk factor surveys. In Northern Sweden the first survey took place in 1986 and the following surveys were performed in 1990, 1994, and 1999, including the age group 25-74 years (the first two surveys were of the age range 25-64 years). Results: From 1985 to 2000, in total 18,105 suspected stroke events, aged 25-74 years, were scrutinized and validated at the central stroke office in Northern Sweden. Of these, 13,908 were found to fulfil the MONICA criteria of an acute stroke. During the period 1985 to 1998, in total 13,228 cases of suspected acute myocardial infarction, aged 25-64 years, were registered. Of these, 8,744 fulfilled the MONICA criteria for acute myocardial infarction. In the four surveys, in total 9,000 randomly selected men and women were invited for survey. Of these 6,952 (77%) participated in the surveys. Conclusion: From 1985 and onwards, the WHO MONICA project has been going on in Northern Sweden. During the whole time the same strict WHO criteria have been followed.