Explanation for the decline in coronary heart disease mortality rates in Auckland, New Zealand, between 1982 and 1993

Abstract

Background: We sought to determine how much of the recent, substantial fall in coronary heart disease (CHD) mortality rates in New Zealand can be attributed to "evidence-based" medical and surgical treatments and how much can be attributed to cardiovascular risk factor reductions.

Methods and results: A cell-based mortality model was developed and refined. This model combined (1) the published effectiveness of cardiological treatments and risk factor reductions with (2) data on all medical and surgical treatments administered to all CHD patients and (3) trends in population cardiovascular risk factors (principally smoking, cholesterol, and hypertension) from 1982 to 1993 in Auckland, New Zealand (population 996 000). Between 1982 and 1993, CHD mortality rates fell by 23.6%, with 671 fewer CHD deaths than expected from baseline mortality rates in 1982. Forty-six percent of this fall was attributed to treatments (acute myocardial infarction 12%, secondary prevention 12%, hypertension 7%, heart failure 6%, and angina 9%), and 54% was attributed to risk factor reductions (smoking 30%, cholesterol 12%, population blood pressure 8%, and other, unidentified factors 4%). These proportions remained relatively consistent after a robust sensitivity analysis.

Conclusions: Approximately half the CHD mortality rate fall in Auckland, New Zealand, was attributed to medical therapies, and approximately half was attributed to reductions in major risk factors. These findings emphasize the importance of a comprehensive strategy that maximizes the population coverage of effective treatments and actively promotes a prevention program, particularly for smoking, diet, and blood pressure reduction.