Have we jugulated the epidemic of heart failure? One swallow does not make a summer . . .

Epidemiology is a useful tool for describing the frequency (incidence and prevalence) of a disease and its demographic and clinical characteristics, in a given population, at a given time. This is what we should call ‘snapshot’ epidemiology. It may also be used to assess the prognosis and outcome in a given cohort of patients during a given follow-up period. Repeating the snapshots at various periods may provide information on changes over time in the frequency and characteristics of the disease. Trends may be generated, which are tempting to analyse as the consequence of changes in patient management throughout the same period. The paper of Stewart et al., in this issue, describes trends in hospitalization for heart failure that occurred from 1990 to 1996 in Scotland. It raises the intriguing hypothesis that the ‘epidemic’ of hospitalization for heart failure in Scotland previously reported between 1980 and 1990, may have peaked around 1993–1994. The authors speculate that this may be a sign of modern-day strategies for the prevention and the treatment of heart failure. Let us first praise the Information and Statistics Division of the National Health Service in Scotland for its Scottish Morbidity Scheme. Thanks to a single individual identifier, the scheme allows data collection on all hospital discharges, and links the data to information on morbidity and mortality held by the General Register Office of Scotland. It is therefore extraordinarily efficient for epidemiological studies. Only a few countries in Europe generate such comprehensive data. Nevertheless, however sophisticated and comprehensive, the data are collected retrospectively and rely heavily on a coding system which relates hospitalization to heart failure as diagnosed by the hospital physician. Given that rapid changes have taken place in awareness, perception and management of cardiovascular disease in general, and of heart failure in particular, the accuracy and reliability of heart failure diagnosis in Scottish hospitals and elsewhere has certainly changed over time. For instance, in the Stewart et al. report, only heart failure