[Seasonal changes in hospitalization and mortality resulting from chronic heart failure in Vigo].

Objectives: Circannual variation in morbi-mortality for ischemic heart disease is well-known but there are few data focusing on chronic heart failure (CHF). This report analyzes seasonal variations in CHF hospitalizations and mortality in Vigo, Northwest of Spain.

Methods: Data on hospital discharge reports with a diagnosis of CHF (3-digit ICD9 code 428) were obtained from the Clinical Documentation Service at Hospital Meixoeiro (419 beds, population: 167.000 inhabitants > 14 years old). Data were divided in three 4-months periods: winter (november-february, years: 1997-98, 98-99 and 99-00), spring (mars-june, years: 97, 98 and 99) and summer (july-october, years: 97, 98 and 99). Hospitalization rates and mortality were also studied at Cardiology, Internal Medicine and Geriatrics (attending to 81% of patients with CHF).

Results: A total of 1.472 CHF hospitalizations were registered (52% male, 83% > 65 years, mean inhospital stay: 13.8 days). Significatives winter increases were noted in global hospitalizations -4.9% (winter) vs. 3.2@1000 (summer) and overall medical services admissions -9.3% (winter) vs. 6.2@1000 (summer). These increases also were observed at specific medical services (Cardiology: +4.9%, Internal Medicine: +6.5%, Geriatrics: +3.2%). There was not seasonal differences in letality or attributable mortality for CHF. Death in patients with a diagnosis of CHF was 4 times more likely. (OR: 3.81; 95% CI: 3.28-4.42).

Conclusions: There are a striking increase in winter hospitalizations for CHF. This diagnosis is associated with an excess of inhospital mortality. Preventive and therapeutic measures taking in account this observation are warranted to reduce the burden of this growing problem.