Background: Previous studies suggested a higher incidence of acute heart failure (AHF) during cold months in regions with cold climate. We examined the daily incidence of AHF by same-day trough temperature and humidity in a warmer region.
Methods and results: All admissions for AHF (340 patients) to a city hospital, providing the sole emergency medical care to a geographical region of approximately 500,000 people were recorded. Patients were followed through admission and for 6 months after discharge. Low minimal trough temperature was associated with an increase in the same-day AHF incidence. Lowest tercile trough night temperatures were associated with higher AHF incidence (3.5 +/- 2.1 versus 2.4 +/- 1.6, events/24 hours, P = .012). This association was mainly from increased AHF events in nights with the predetermined trough temperature of <7 degrees C (4 +/- 2.1 versus 2.5 +/- 1.7, events/24 hours, P = .0013). This association persisted even after excluding the coldest consecutive 30 days from the analysis. Humidity was not associated with increased AHF event rate. In a post-hoc analysis we have observed doubling of 6-month mortality in patients admitted with AHF during days with lower trough night temperature, despite no apparent worse baseline characteristics or disease severity at admission.
Conclusions: AHF rate is increased during days with lower trough night temperature. If confirmed, these results may have implications on issues related to climate control in houses of the elderly or patients susceptible to heart failure.