Oslo Study Diet and Antismoking Trial. Results after 102 months

The five year (60-month) results from the Oslo Study Diet and Antismoking Trial were published in the Lancet in December 1981. The trial involved 1,232 healthy men, aged 40 to 49 years, at high risk for coronary heart disease, with serum cholesterol values in the range of 7.5 to 9.8 mmol/liter (enzymatic method: 6.9 to 9.0, mean value 7.8 mmol/liter). Eighty percent of the men were daily cigarette smokers at the start of the study, and all participants were normotensive, i.e., systolic blood pressure was less than 150 mm Hg. Subjects were randomly assigned to either a control or intervention group. Follow-up visits were scheduled every six months for the intervention group and yearly for the control group. Once the trial was completed, the regular six-month follow-up visits were discontinued, but eight to nine years (96 to 108 months) after the start of the trial, participants were called for a new follow-up. Risk factors were recorded, and clinical events were diagnosed according to the same procedure as during the trial. The mean serum cholesterol levels in the intervention group remained unchanged three years after the end of the trial, but the cholesterol levels in the control group declined. Daily cigarette smoking increased in the intervention group but remained stable in the control group. At the new follow-up, the difference in incidence of fatal and nonfatal myocardial infarction and sudden coronary death was the same as at the end of the trial three years earlier, yielding significant differences between the two groups for sudden death, total coronary death, and total coronary events. Although the study was not designed to show differences in total mortality, this difference became marginally significant, with 19 deaths in the intervention group and 31 in the control group. It is concluded that although net differences in risk factors between the two groups had been reduced during the three years after the regular intervention period, the significant difference in coronary events and sudden death was maintained.