Lisa von Huth Smith and Torben Jørgensen
Research Centre for Prevention and Health, DK-2600 Glostrup
Determinants for increasing physical activity in the general population – the Inter99 study
Background: There is a lack of knowledge on which factors are of importance for increased physical activity among individuals at high risk for developing ischemic heart disease (IHD). Knowledge within this area is of essential importance in the planning of future interventions aimed at decreasing the incidence of ischemic heart disease and other diseases resulting from physical inactivity. The objective of the present study was to identify predictors of successful maintenance/increase of physical activity in a populationbased intervention study.
Material and Methods: The study population comprises 61.301 persons. A random sample of 13.016 persons was invited for a risk assessment for IHD by means of a computer program (PRECARD). The remaining 48.285 served as reference population. According to predefined criteria participants were classified into a high risk and a low risk group. The 13.016 persons were a priori randomised to receive a high intensity or a low intensity intervention. Those at high risk received individual lifestyle counselling. Individuals in the high intensity intervention group were furthermore offered lifestyle counselling in groups on smoking cessation and/or physical activity/diet over a 6-month period. Individuals in the low intensity intervention group were referred to their GP. Interventions were made in three waves (at baseline, after one year, and after three years). Changes in physical activity were monitored by questionnaires.
Results: Among men there was a weak and insignificant association between intervention intensity and successful maintenance/increase of physical activity (OR 1.16 (95% CI 0.87-1.57)). This association was stronger though insignificant in high-risk men (OR 1.30 (95% CI 0.76-2.21)). Among women there was no association between intervention group and successful maintenance/increase of physical activity. High-risk men were significantly less likely to maintain/increase physical activity than low-risk men (OR 0.75 (95% CI 0.62-0.91)). This association was weaker and insignificant among women (OR 0.86 (95% CI 0.69-1.06)). Among high-risk men prudent diet was significantly associated with maintained/increased physical activity (OR 1.91 (95%CI 1.14-3.22)). Among women there was an insignificant tendency towards an association between diabetes and successful maintenance/increase of physical activity (known diabetes mellitus, OR 1.32 (95% CI 0.49-3.55), newly discovered diabetes mellitus OR 1.36 (95% CI 0.67-2.74)). This association was also found among high-risk women (known diabetes mellitus OR 1.44 (95% CI 0.51-4.00), newly discovered diabetes mellitus OR 1.68 (95% CI 0.79-3.53)). There was no association between diabetes mellitus and successful maintenance/increase of physical activity among men. More results will be presented at the symposium.
Conclusion: The present study showed no substantial effect of high-intensity intervention compared to low intensity intervention on successful maintenance/increase of physical activity after one year. This finding should be compared to changes in physical activity in the reference population. Analysis of the effect of repeated high-intensity intervention after one year and after three years will be carried out to evaluate the effect of repeated lifestyle intervention. Furthermore, the study indicates that predictors of successful maintenance/increase of physical activity in an intervention study are different for men and women.
