Contribution of trends in survival and coronary-event rates to changes in coronary heart disease mortality: 10-year results from 37 WHO MONICA project populations. Monitoring trends and determinants in cardiovascular disease.

BACKGROUND

The WHO MONICA (monitoring trends and determinants in cardiovascular disease) Project monitored, from the early 1980s, trends over 10 years in coronary heart disease (CHD) across 37 populations in 21 countries. We aimed to validate trends in mortality, partitioning responsibility between changing coronary-event rates and changing survival.

METHODS

Registers identified non-fatal definite myocardial infarction and definite, possible, or unclassifiable coronary deaths in men and women aged 35-64 years, followed up for 28 days in or out of hospital. We calculated rates from population denominators to estimate trends in age-standardised rates and case fatality (percentage of 28-day fatalities=[100-survival percentage]).

FINDINGS

During 371 population-years, 166,000 events were registered. Official CHD mortality rates, based on death certification, fell (annual changes: men -4.0% [range -10.8 to 3.2]; women -4.0% [-12.7 to 3.0]). By MONICA criteria, CHD mortality rates were higher, but fell less (-2.7% [-8.0 to 4.2] and -2.1% [-8.5 to 4.1]). Changes in non-fatal rates were smaller (-2.1%, [-6.9 to 2.8] and -0.8% [-9.8 to 6.8]). MONICA coronary-event rates (fatal and non-fatal combined) fell more (-2.1% [-6.5 to 2.8] and -1.4% [-6.7 to 2.8]) than case fatality (-0.6% [-4.2 to 3.1] and -0.8% [-4.8 to 2.9]). Contribution to changing CHD mortality varied, but in populations in which mortality decreased, coronary-event rates contributed two thirds and case fatality one third.

INTERPRETATION

Over the decade studied, the 37 populations in the WHO MONICA Project showed substantial contributions from changes in survival, but the major determinant of decline in CHD mortality is whatever drives changing coronary-event rates.