OBJECTIVE To estimate the fall in coronary heart disease (CHD) mortality in Scotland attributable to medical and surgical treatments, and risk factor changes, between 1975 and 1994.

DESIGN A cohort model combining effectiveness data from meta-analyses with information on treatment uptake in all patient categories in Scotland.

SETTING AND PATIENTS The whole Scottish population of 5.1 million, including all patients with recognised CHD.

INTERVENTIONS All cardiological, medical, and surgical treatments, and all risk factor changes between 1975 and 1994. Data were obtained from epidemiological surveys, routine National Health Service sources, and local audits.

MAIN OUTCOME MEASURES Deaths from CHD in 1975 and 1994.

RESULTS There were 15 234 deaths from CHD in 1994, 6205 fewer deaths than expected if there had been no decline from 1975 mortality rates. In 1994, the total number of deaths prevented or postponed by all treatments and risk factor reductions was estimated at 6747 (minimum 4790, maximum 10 695). Forty per cent of this benefit was attributed to treatments (initial treatments for acute myocardial infarction 10%, treatments for hypertension 9%, for secondary prevention 8%, for heart failure 8%, aspirin for angina 2%, coronary artery bypass grafting surgery 2%, and angioplasty 0.1%). Fifty one per cent of the reduction in deaths was attributed to measurable risk factor reductions (smoking 36%, cholesterol 6%, secular fall in blood pressure 6%, and changes in deprivation 3%). Other, unquantified factors apparently accounted for the remaining 9%. These proportions remained relatively consistent across a wide range of assumptions and estimates in a sensitivity analysis.

CONCLUSIONS Medical treatments and risk factor changes apparently prevented or postponed about 6750 coronary deaths in Scotland in 1994. Modest gains from individual treatments produced a large cumulative survival benefit. Reductions in major risk factors explained about half the fall in coronary mortality, emphasising the importance and future potential of prevention strategies.