Improvements in treatment of coronary heart disease and cessation of stroke mortality rate decline

Abstract

Background and purpose: Many countries observed rapidly declining stroke mortality rates during 1970-1990, followed by a slowing or a cessation of this decline. This slowing was seen for both sexes and all ages. Here we test the hypothesis that improvements in coronary heart disease (CHD) survival can explain this slowing through an increase in the number of CHD survivors at an increased risk for stroke.

Methods: We created multistate life-table models based on the survival experience of 46 years of follow-up of the Framingham Heart Study cohort. Improvements in survival after CHD were modeled by decreasing mortality rates for those with CHD. We analyzed whether improved CHD survival could result in a >3% increase in annual stroke mortality rates, which would be enough to eliminate the previously observed decline.

Results: CHD survival improvements led to an increase in the number of stroke deaths but also a concomitant increase in the total population size. Under no circumstances was there an annual increase in stroke mortality rates approaching 3% for both sexes and for younger and older age groups.

Conclusions: The hypothesis that increases in the numbers of people with CHD, as a consequence of improvements in CHD survival, explain the observed slowing of the stroke mortality rate decline must be rejected. The true explanation is also likely to be a factor that changed markedly around 1990, but with more direct effects on stroke mortality.