Abstract 033: Final Results from One of World’s Largest Population-Based Randomized Interventions on Lifestyle. The Inter99 Study
Background: unhealthy lifestyle is the most important factor with impact on ischemic heart disease (IHD) and mortality. In general, population-based lifestyle interventions have shown disappointing results. The Inter99 study is one of the largest randomized population-based lifestyle interventions in the world. After five years we found promising improvements in lifestyle in the intervention group: significantly higher smoking abstinence rates, decreased binge drinking, increased intake of fruit/vegetables, decreased intake of saturated fat, and increased physical activity in men - compared with the control group.
Methods: Inter99 is a randomized controlled trial in a general population. The aim was to prevent IHD by a non-pharmacological intervention. We included 61,301 persons, 30-60 years old, living in The Capital Region of Denmark. A total of 11.708 were pre-randomized to the high intensity intervention group; 6,091 accepted to participate and were offered physical examination, IHD-risk screening/assessment and lifestyle counselling (non-smoking, healthy food, low alcohol intake and non-sedentary behaviour) both individually and group-based. Participants at high risk of IHD were offered re-examinations and repeated counselling at one-, three- and five-year follow-up. Participants at low risk of IHD were offered re-examination and counselling at five-year follow-up and completed questionnaires at one- and three-year follow-up. All participants received questionnaires after ten years. A sample in the control group received questionnaires only. We obtained information on the incidence of IHD and stroke from national central registers - comparing all persons in the high intensity intervention group with all persons in the control group, ten years after study start. We used Cox proportional hazard with time as underlying variable, and sex, age, ethnicity, education and cohabitation-status as confounder. Emigrated persons were excluded. Analyses were performed in persons with full information.
Results: There were 546 cases of IHD and 321 of stroke in the high intensity intervention group, and 2,142 of IHD and 1,364 of stroke in the control group after ten years. There was no significant effect of the intervention on prevalence of IHD (HR=1.04 (95%CI=0.95-1.14)) or stroke (HR=0.99 (95%CI=0.88-1.12)). For stroke we found significant interaction between age and sex, which was included in the final model. There was no interaction with group.
Conclusion: This large population-based intervention trial did not reduce the incidence of IHD or stroke after ten years - despite a significant effect on lifestyle after five years. As population-based lifestyle interventions repeatedly have shown disappointing results we suggest that it is time to discuss whether we should leave this approach definitely, and focus on structural changes in the environment instead.
- © 2013 by American Heart Association, Inc.