Background Peaks and troughs in cardiovascular events correlated with seasonal change is well established from an epidemiological perspective but not a clinical one.

Methods Retrospective analysis of the recruitment, baseline characteristics and outcomes during minimum 12-month exposure to all four seasons in 1598 disease-management trial patients hospitalised with chronic heart disease. Seasonality was prospectively defined as ≥4 hospitalisations (all-cause) AND >45% of related bed-days occurring in any one season during median 988 (IQR 653, 1394) days follow-up.

Results Patients (39% female) were aged 70 ± 12 years and had a combination of coronary artery disease (58%), heart failure (54%), atrial fibrillation (50%) and multimorbidity. Overall, 29.9% of patients displayed a pattern of seasonality. Independent correlates of seasonality were female gender (adjusted OR 1.27, 95% CI 1.01–1.61; p = 0.042), mild cognitive impairment (adjusted OR 1.51, 95% CI 1.16–1.97; p = 0.002), greater multimorbidity (OR 1.20, 95% CI 1.15–1.26 per Charlson Comorbidity Index Score; p < 0.001), higher systolic (OR 1.01, 95%CI 1.00–1.01 per 1 mmHg; p = 0.002) and lower diastolic (OR 0.99, 95% CI 0.98–1.00 per 1 mmHg; p = 0.002) blood pressure. These patients were more than two-fold more likely to die (adjusted HR 2.16, 95% CI 1.60–2.90; p < 0.001) with the highest and lowest number of deaths occurring during spring (31.7%) and summer (19.9%), respectively.

Conclusions Despite high quality care and regardless of their diagnosis, we identified a significant proportion of “seasonal frequent flyers” with concurrent poor survival in this real-world cohort of patients with chronic heart disease.