The Oslo Ischaemia Study: cohort profile

Abstract

Purpose: The Oslo Ischaemia Study was designed to investigate the prevalence and predictors of silent coronary disease in Norwegian middle-aged men, specifically validating exercise electrocardiography (ECG) findings compared with angiography. The study has been important in investigating long-term predictors of cardiovascular morbidity and mortality, as well as investigating a broad spectrum of epidemiological and public health perspectives.

Participants: In 1972-1975, 2014 healthy men, 40-59 years old, were enrolled in the study. Comprehensive clinical examination included an ECG-monitored exercise test at baseline and follow-ups. The cohort has been re-examined four times during 20 years. Linkage to health records and national health registries has ensured complete endpoint registration of morbidity until the end of 2006, and cancer and mortality until the end of 2017.

Findings to date: The early study results provided new evidence, as many participants with a positive exercise ECG, but no chest pain ('silent ischaemia'), did not have significant coronary artery stenosis after all. Still, they were over-represented with coronary disease after years of follow-up. Furthermore, participants with the highest physical fitness had lower risk of cardiovascular disease, and the magnitude of blood pressure responses to moderate exercise was shown to influence the risk of cardiovascular disease and mortality. With time, follow-up data allowed the scope of research to expand into other fields of medicine, with the aim of investigating predictors and the importance of lifestyle and risk factors.

Future plans: Recently, the Oslo Ischaemia Study has been found worthy, as the first scientific study, to be preserved by The National Archives of Norway. All the study material will be digitised, free to use and accessible for all. In 2030, the Oslo Ischaemia Study will be linked to the Norwegian Cause of Death Registry to obtain complete follow-up to death. Thus, a broad spectrum of additional opportunities opens.

Keywords: coronary heart disease; echocardiography; epidemiology; public health.

Figure 1

Baseline examination outline for one subject during the examination day. ECG, electrocardiography.

Figure 2

Flowchart of clinical examinations and follow-ups in the Oslo Ischaemia Study. Complete endpoint registration for morbidity to 1 January 2007†, and for cancer and total mortality to 31 December 2017‡.

Figure 3

Cases and cumulative incidence of cardiovascular disease†, cancer and death over 45 years follow-up in initially healthy middle-aged men. †Cardiovascular diseases included fatal or non-fatal myocardial infarction, angina pectoris, heart failure, ischaemic or haemorrhagic stroke, transitory ischaemic attack, abdominal aortic aneurysm, claudicatio intermittens and revascularised peripheral artery disease. This follow-up ended on 1 January 2007.