Background: Trends in risk factors provide important information for public health programmes. The relative importance of risk factors may change in new generations. It is essential to discover unfavourable trends.
Material and methods: Cross-sectional data for 40-year olds from three counties in Norway (Finnmark, Oppland, Oslo) were retrieved from health surveys conducted by the National Health Screening Service/Norwegian Public Health Institute and the health authorities in Oslo in the period 1972-2003.
Results: Mean body mass index (BMI) for 40-year olds has increased substantially in all counties (1.9-2.5 kg/m2 , p = 0.001 for both sexes). Mean serum cholesterol levels have been reduced by 1.1 mmol/L in Finnmark, and by 0.5-0.6 mmol/L in the other counties (p <0.001). The proportion of daily smokers has been reduced by 20% points for men, but the proportion reporting to be sedentary in leisure time has increased (p = 0.005). Marked differences between geographical regions still exist in Oslo for daily smoking and physical inactivity, and BMI for women has increased.
Interpretation: Previously reported favourable and unfavourable trends for risk factors continue. The increase in BMI has been most intense in the last 10 years. The regional differences within Oslo are larger than the differences between the counties.