What MONICA told us about stroke.

The WHO MONICA (Multinational Monitoring of Determinants and Trends in Cardiovascular Disease) Project is the world's largest prospective study on cardiovascular disorders. In the stroke component, 34,715 individually validated stroke events were recorded; these happened during 21.7 million years of observation in 14 populations in Europe, Siberia, and China. Two important questions were addressed. What is driving stroke mortality trends-changes in stroke incidence (risk of stroke) or changes in survival? To what extent do changes in the population burden of classic cardiovascular risk factors affect stroke risk in the population? The seven lessons that I learnt from the MONICA study are described; some were about the limitations of an ecological study for testing of hypotheses and evaluation of community-based intervention programmes. Socioeconomic factors seem more important than classic risk factors for the establishment of stroke trends in the population, best shown by the development of stroke mortality in eastern Europe during the 10 years of the WHO MONICA Project. The simplest, most important, and, for clinicians, the most encouraging of the lessons is that quality of stroke care makes a profound difference, not only to the patient and his or her family but also to the burden of stroke in the population at large.