P1083Seasonal trends in risk for patients admitted to hospital with heart failure

Abstract

Background: Heart failure is among the most common reasons for admission to hospital and is associated with high rates of readmission. Studies have shown that the frequency of heart failure hospitalisation in temperate climates increases in winter months. While such findings suggest that the risk of hospitalisation is higher in winter as compared to summer months, there has been little evaluation of whether there is seasonal variation in the readmission risk of patients who are hospitalised for heart failure. Purpose(s): To examine seasonal variations in: 1) readmission risk for patients hospitalised with heart failure; and 2) frequency of heart failure hospitalisation for patients at different risk of readmission. Method(s): We performed a retrospective study of United States Medicare beneficiaries age >=65 who were hospitalised for heart failure between January 1, 2009 and June 30, 2015. We used a predictive model for 30-day unplanned hospital readmission to assign each hospitalisation a predicted risk of readmission; this model adds demographic and prior utilization data to the hospital-wide readmission model used by the Centres for Medicare and Medicaid Services (CMS). Each hospitalisation was categorized as lowest 20%, middle 60%, and highest 20% of predicted readmission risk. We calculated rate of hospitalisations per calendar month, predicted readmission risk, and monthly rate of hospitalisations for each risk stratum in the study period; monthly hospitalisations were standardized to 30 days. When comparing risk strata, we divided the totals for the middle 60% stratum by three. Result(s): Among 2,661,837 heart failure hospitalisations, we observed the highest rates of hospitalisation in January through March (range 37,185-37,949 per month) and the lowest rates in July through September (range 29,901-30,603 per month). Conversely, predicted readmission rates were lowest in January and highest in August, with rates of 23.1% and 24.0%, respectively. The number of hospitalisations increased in winter months for patients in all three risk strata, with greatest variation in seasonal differences observed for patients in the lowest 20% of predicted risk (Figure). For example, hospitalisation rates for highest risk patients were 7058 per 30 days in January versus 6473 per 30 days in August; for lowest risk patients, these values were 7852 versus 5595, respectively. (Figure Presented) Conclusion(s): Readmission risk decreased in winter versus summer months for patients hospitalised for heart failure. Much of the seasonal variation in heart failure hospitalisations appears to be due to a large excess of hospitalisations of these low risk patients in winter months. Our results suggest that preventative measures, such as vaccinations or dietary education, that target lower risk patients in colder months may reduce overall utilisation.