Response by Christiansen et al to Letters Regarding Article, “Age-Specific Trends in Incidence, Mortality, and Comorbidities of Heart Failure in Denmark, 1995 to 2012”
Authors: Mia Nielsen Christiansen, Lars Køber, Charlotte Andersson
Journal: Circulation (2017)

In Response:We thank Gabet and Kaul and their colleagues for their interest in our article and important discussions.Gabet et al 1 pointed out that hospitalization rates for heart failure (HF) among young adults in France between 2000 and 2012 was stable (in contrast with declining rates in older individuals) despite an increase in prevalence of obesity and diabetes mellitus.Therefore, they suggested that other factors may underlie our observations of increasing HF incidence rates.Similar trends in hospitalizations have also been noted in the United States and Slovenia. 2,3lthough we certainly agree that more studies are needed to understand the mechanisms behind our and others observations, caution is needed when comparing HF incidence rates with HF hospitalization rates because these are not necessarily measuring the same thing.Changes in hospitalization rates may depend on the incidence of the condition as well as reflect changes in patient management, including hospitalization versus outpatient management and associated mortality.For instance, some data suggest that more patients are managed primarily on an outhospital basis today compared with a decade ago.The proportion of patients managed primarily by outhospital visits likely varies depending on multiple factors, including national variation, hospital capacity, age, etiology, and HF severity. 4,5imilar to our study, Kaul et al 6 observed diverse trends in incidence of HF in a large region of Canada for young versus old individuals, with significant declines in older but not younger individuals.For young men, incidence rates were increasing.In addition, Kaul et al 6 noted that half of the young patients were diagnosed in the outpatient setting, compared with 38% for older individuals.As a sensitivity analysis presented in our online supplementary material, we included patients diagnosed in the outpatient setting, which did not alter the results, but we did not look further into which types of patients were diagnosed in the outpatient setting or whether this pattern has changed over time. 7We also did not look at the burden of future hospitalizations, which might have yielded additional insights.Clearly, as illustrated by the similarities and discrepancies in data between studies, the current HF epidemiology in young adults needs careful interpretations.Although much data suggest that the HF incidence among young individuals has unfortunately not followed the declines observed for older individuals and because mortality is substantial, further efforts are needed to better understand the trends in young adults.Given the overall rarity of the condition, spatial differences, disparities in population characteristics, and heterogeneity in diagnostic criteria between studies, we agree with Kaul and colleagues 6 that a collaborative research consortium could be a great opportunity to provide further important insights into this subject.