Preventing Heart Attack and Stroke    
A History of Cardiovascular Disease Epidemiology
North Karelia Project
stroke

Background: This study was a pioneer systematic community-wide intervention to reduce population levels of CVD risk factors and measure disease effects in the eastern Finnish province of North Karelia and evaluate the results of this sustained health promotional campaign. There the Seven Countries Study had demonstrated high CVD risk and its correlates. Reductions in cigarette smoking, serum cholesterol concentrations, and blood pressure were among the immediate objectives of this community-based campaign. An additional objective was to promote the early detection, treatment, and rehabilitation of patients with CVD.

The study was carried out in the province of North Karelia, a rural area of 180,000 inhabitants, with the reference area of Kuopio Province, Finland.

Methods: In the 3 cross-sectional surveys carried out in 1972, 1977, and 1982, a random sample of 1/16th of the population was drawn: 1,834 men and 1,973 women from North Karelia and 2,665 men and 2,769 women from the reference area (Kuopio) were studied between the ages of 30-59 years. Kuopio was selected as the control area due to its relative similarity to North Karelia. The project was called a quasi- experimental community-based CVD demonstrated program and the cohort and community were followed through 1997.

Five years later a cross-sectional survey was carried out in both study areas using methods similar to those employed in the baseline survey. The sample for this second survey consisted of those between the ages of 30 and 64 years. Additional cross sectional population surveys were carried out every 5 years in 1982, 1987, 1992, and 1997. Over the more recent periods under study (1982-1992), risk factor surveys were carried out as part of the WHO sponsored MONICA study and also as part of the WHO CINDI program. The 1992 and 1997 surveys were expanded to additional areas of Finland to assess the effectiveness of a country-wide chronic disease prevention program. In 1982, portions of southwestern Finland were added to the survey sample, then in 1992, the Helsinki metropolitan area was added, and in 1997 the northern province of Oulu was surveyed. Similar to earlier surveys, an independent random sample was drawn from existing population registers.

A comprehensive questionnaire was sent to the homes of the surveyed sample asking questions about socioeconomic status, medical history, smoking, diet, alcohol consumption, physical activity (and attempts to change these lifestyle behaviors), and psychosocial factors. At the clinic examination, height, weight, skinfold thicknesses, blood pressure, and serum cholesterol were measured.

Information was given to the general public of the education province about practical means to modify coronary risk factors by mass and local media; by systematically integrating the program into existing services; by training volunteers and community leaders in the practical tasks of the program; and through population-wide environmental changes (e.g., smoking restrictions, use of low-fat dairy and meat products); and through the use of internal information services to support the activities of the study.

An important focus of the overall program was to reduce population serum cholesterol levels through dietary change because of the presumed role in the high CVD rates of Finland. This was accomplished through widespread reductions in saturated fat intake and concomitant increases in the consumption of vegetables and polyunsaturated fats. The intervention was originally designed to be implemented throughout the community for 5 years (1972-1977) but the program was gradually expanded to include the prevention of other non-communicable diseases.

Results: At baseline, the prevalence of CHD risk factors was high. Approximately 52% of men aged 25-59 years were current smokers, their average serum cholesterol level was 269 (mg/dl), and the average blood pressure was 147/91 (mmHg). Participation rates in the baseline survey were excellent (>90%) in both North Karelia and in the reference area. In the 1977 survey, these rates were approximately 90% in the two study areas; participation rates of approximately 80% in North Karelia and 82% in the reference area were observed in the 1982 survey.

Over the first 10 years of this program (1972-1982), cigarette smoking rates were lowered in men in North Karelia compared to men living in the reference area. The differences were less with women. The program measured positive effects on average serum cholesterol concentrations in men and lesser reductions in women. The intervention activities also apparently resulted in significant reductions in systolic and diastolic blood pressure in both men and women. The reductions in risk factor levels observed in North Karelia during the first 10 years of the program were 36% in men smokers, 11% in average serum lipid levels, and 5% average diastolic blood pressure. The results were in a similar direction for women but to a lesser extent.

Favorable long-term trends in the prevalence and magnitude of the principal coronary risk factors were observed between the intervention and reference areas over a 15 year follow-up period (1987). Average total serum cholesterol levels in men declined to a greater extent in North Karelia compared to the reference area of Kuopio while decreases in this risk factor were similarly observed in women from the intervention and control areas. The proportion of men who regularly smoked declined in North Karelia from 52% to 36% and from 50% to 41% in Kuopio over this period. There were no significant differences between the 2 study communities in the proportion of either men or women who were found hypertensive.

Low fat milk was increasingly consumed over time in both North Karelia and in Kuopio, by 1982, in approximately 40% of persons surveyed. Between 1972 and 1982, whole milk and sour milk consumption declined by 12% in North Karelia men and by 7% in men living in the reference area of Kuopio. These milk consumption patterns declined by 17% among women living in North Karelia and by 11% of those residing in Kuopio. Changes in the type of fat spread used on bread were also seen with a particularly pronounced effect during the initial 5 years of recommended dietary changes. There was a significant net reduction in saturated fat intake of 20% in men and 14% in women over the first 10 years under study. These dietary changes were associated with a significant reduction in average total cholesterol levels in men residing in North Karelia compared to the reference area of Kuopio; however, these changes were not seen in women.

CVD risk factors under study over a 25 year follow-up (1972-1997), in both men and women showed continued declines in serum cholesterol and systolic blood pressure levels. Smoking prevalence in men from North Karelia declined from 52% in 1972 to 31% in 1997. Essentially similar trends were observed in Kuopio (50% in 1972; 31% in 1997), however. In women, who continued to smoke at much lower rates than men, smoking rates actually increased over time in both the intervention and comparison areas. In 1972, 10% of women from North Karelia were current smokers whereas 16% were current smokers in 1997. In the Kuopio reference area, 11% in 1972 and 17% in 1997.

Over the course of the study, mortality from CHD declined in North Karelia by 73% and by 65% throughout Finland. In men, mortality from cerebrovascular disease and lung cancer also declined in men and women and more in Karelia than Kuopio.

Discussion: This pioneer community-based program aimed at the primary and secondary prevention of CVD was initiated in direct response to local demand that public health activities be carried out to reduce the high rates of CVD documented in Eastern Finland. The prevalence and levels of several CVD risk factors declined over time though strong secular trends attenuated some of the observed differences. The data from this project suggest that community intervention programs may favorably influence the risk factors for CVD over and above nationwide trends. However, much is left to study about the more efficient ways to accelerate such changes in communities.

Keywords: community intervention; North Karelia Project; cohort studies; Finland.

Reference:

North Karelia Project, February 2006, ProCOR, www.procor.org.

Puska P, Tuomilehto J, Salonen J, Neittaanm L, Maki T, et al, (1979). Changes in coronary risk factors during comprehensive five-year community programme to control cardiovascular diseases (North Karelia project). Br Med J, 2: 1173-78.

Puska P, Salonen JT, Tuomilehto J, Nissinen A, Kottke TE (1983). Evaluating community-based preventive cardiovascular programs: problems and experiences from the North Karelia project. J Comm Health, 9: 49-64.

Puska P, Salonen J, Nissinen A, Tuomilehto J (1983). The North Karelia project. Prev Med, 12: 191-5.

Pietinen P, Nissinen A, Vartiainen E, Tuomilehto A, Uusitalo U, et al, (1988). Dietary changes in the North Karelia Project (1972-1982). Prev Med, 17: 183-93.

Vartiainen E, Jousilahti P, Alfthan G, Sundvall J, Pietinen P, et al, (2000) Cardiovascular risk factor changes in Finland, 1972-1997. Int J Epidemiol, 29: 49-56.

stroke North Karelia Province, Finland