Objective: The Oslo Diet and Antismoking study was a 5-year randomised trial initiated in 1972-1973, which studied the effect of dietary change and smoking cessation for the prevention of coronary heart disease among high-risk middle-aged men. To test the long-term maintenance of lifestyle change, we examined diet and cardiovascular risk factors in subjects initially randomised to the control and intervention groups 20 years after cessation of the intervention.
Subjects and design: Of the original cohort that included 1232 participants, 910 survivors were identified in 1997 and cardiovascular risk factors were measured in 563 (62%) in 1997-1999. Of these, 558 (99%) also completed questionnaires about their food intake and attitudes to health and diet.
Results: Cigarette smoking was nearly halved between baseline and 20-year follow-up in each of the intervention and control groups (P<0.001 within groups), but did not differ between the intervention group (39%) versus the control group (34%); P=0.07. Body mass index increased by 1.4+/-2.6 and 1.6+/-2.6 kg/m(2) between baseline and 20-year follow-up in the intervention and control groups, respectively (P<0.001 within groups; NS between groups). Serum total cholesterol and triglyceride concentrations decreased substantially in subjects treated or untreated with statins (P<0.001 within the intervention and control groups) but did not differ between the groups (total cholesterol change of -1.4+/-1.3 and -1.3+/-1.2 mmol/l, respectively, and triglyceride change of -0.5+/-1.0 mmol/l in both groups). Men in the intervention group reported a less atherogenic fat quality score and lower intakes of fat, saturated fat and cholesterol, higher intakes of long chain polyunsaturated fatty acids, protein and beta-carotene and greater attention to lifestyle and change of diet than the control group (all P<0.05). The fatty acid concentrations did not differ, however, between the intervention and control groups (P>0.05).
Conclusions: No long-term differences in smoking rates or lipid concentrations between the intervention and control groups were observed in the surviving attendees two decades after the end of the trial. Lifestyle intervention still influenced the dietary intake, though modestly.