There were 419 551 incident cases of heart failure in Ontario from 1997 to 2007, of which 216 190 patients required admission to hospital and 203 361 patients were cared for in an outpatient setting at the time of initial diagnosis (). Women accounted for 51% of the study population, and patients aged 65 years or older represented 80% of the overall cohort.
Figure 1: Flow of patients through the study, Apr. 1, 1997, to Mar. 31, 2007. *Either an admission to hospital in which heart failure is listed under any diagnostic field in the Discharge Abstract Database or an outpatient visit associated with a claim for heart (more ...)
Compared with patients whose heart failure was diagnosed in the outpatient setting, patients admitted to hospital at the time of the initial diagnosis were older (median age 77 v. 76 yr, p < 0.001) and had more comorbidities (mean Charlson–Deyo score 2.1 v. 1.0, p < 0.001) (). Compared with outpatients, patients in hospital had higher rates of ischemic heart disease (inpatients 50.4%; outpatients 25.5%, p < 0.001), diabetes (inpatients 28.2%; outpatients 13.8%, p < 0.001) and hypertension (inpatients 41.8%; outpatients 23.9%, p < 0.001).
Characteristics of patients with incident heart failure by clinical site of diagnosis
The characteristics of patients with newly diagnosed heart failure showed similar trends over time regardless of the setting in which the initial diagnosis was made. Between 1997 and 2007, the median age at diagnosis increased by 2 years among inpatients (p < 0.001) and by 1 year among outpatients (p < 0.001) (). There was an increase in mean Charlson–Deyo comorbidity score from 1.9 to 2.3 among inpatients (p < 0.001) and from 1.0 to 1.1 among outpatients (p < 0.001). The prevalence of diabetes increased from 26.1% to 34.6% among inpatients (p < 0.001) and from 12.9% to 16.4% among outpatients (p < 0.001). The prevalence of hypertension similarly increased, from 35.7% to 47.2% among inpatients (p < 0.001) and from 21.5% to 25.2% among outpatients (p < 0.001). In contrast, the prevalence of ischemic heart disease decreased from 54.4% to 44.0% among inpatients (p < 0.001) and from 26.8% to 23.7% among outpatients (p < 0.001).
Characteristics of patients with incident heart failure by clinical site and time of diagnosis
Trends in the incidence of heart failure
The age- and sex-standardized incidence rate of heart failure decreased by 32.7% from 454.7 per 100 000 people to 306.1 per 100 000 people (p < 0.001) during the study period (). The decline in the incidence of heart failure occurred in both inpatient and outpatient settings.
Temporal trends in incidence of heart failure
The age-standardized incidence rates among men and women were not significantly different and decreased comparably throughout the study period (). In contrast, the sex-standardized incidence of heart failure increased with age (). Although the sex-standardized incidence of heart failure decreased over time, the rate of decline was highest among patients aged 85 years and older.
Age-standardized trends in incidence of heart failure, by sex.
Sex-standardized trends in incidence of heart failure, by age group.
Outcomes after diagnosis of heart failure
Between 1997 and 2007, 1-year risk-adjusted mortality decreased nonlinearly from 17.7% to 16.2% among outpatients (p = 0.02) and from 27.0% to 25.2% among all patients (p = 0.03), with a nonsignificant decrease of 35.7% to 33.8% among inpatients (p = 0.1)(). Among inpatients who survived to discharge, the 1-year risk-adjusted rate of readmission for heart failure decreased from 13.4% to 10.5% (p = 0.02) and the 1-year risk-adjusted all-cause readmission rate decreased from 49.0% to 45.6% (p = 0.001).
Temporal trends in crude and risk-adjusted mortality and readmission rates, per 100 patients
A sensitivity analysis of incident heart failure cases identified using a 1-outpatient-claim method as opposed to a 2-claim method showed similar declines in 1-year risk-adjusted mortality rates. The risk of incident heart failure decreased from 16.7% to 15.0% among outpatients (p
= 0.004), from 35.2% to 33.1% among inpatients (p
= 0.1), and from 23.1% to 20.9% among all patients (p
= 0.005) (Appendix 1, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.111958/-/DC1
). Adopting a 1-claim method had a small impact on the number of incident cases identified in the inpatient setting, and, thus, trends in readmission rates were comparable with those found using the 2-claim method.