Seasonal variation in hospital admission in patients with heart failure and its effect on prognosis.

Background: A seasonal variation in hospital admissions in patients with heart failure (HF) has been described and most admissions occur during the winter season. The effect of this seasonal variation on prognosis is less clear.

Objectives: To evaluate the effect of the seasonal timing of hospital admission on clinical outcome in patients with HF.

Methods: We prospectively enrolled 362 consecutive patients hospitalized with a definite clinical diagnosis of HF during a 2-year period. Patients were followed clinically for a period of 1 year.

Results: There was a prominent seasonal variation in hospital admissions in patients with HF with peak admissions during the winter. The admission rate inversely correlated with the average monthly temperature. Admission during the summer season was a significant predictor of reduced survival (59 vs. 75%, p < 0.01). Cox regression analysis demonstrated that independent predictors of reduced survival after adjustment for other predictors were admission during the hottest 6 months or admission during the summer. In addition, increased mean environmental admission temperature was an independent predictor of reduced survival.

Conclusions: Seasonal temperature has a significant effect on the rate of hospital admission in patients with HF. Admission during warmer weather is a sign of a poor prognosis.