The effect of temperature on illness severity in emergency department congestive heart failure patients

Previous studies revealed fewer visits for congestive heart failure (CHF) to emergency departments (EDs) in New Jersey, USA and fewer admissions for CHF to a Southern Indian and an Israeli hospital during warmer months. Using hospital admission rate for CHF as a marker for illness severity, we hypothesized that CHF would also be less severe in warmer months.

This is a retrospective cohort study which included all ED visits from 1 January 2004 to 31 January 2006. We analysed the monthly CHF hospital admission rates. We a priori chose to compare the admission rates for the 4 warmest to the 4 coldest months.

Of a total of 136,347 ED visits, 1083 (0.8%) were accounted for CHF. Hospital admission rate was 55.8%. Although there was a statistically significant increase in ED visits for CHF during the colder months, the 4 warmer months from June to September had 1.15 times higher hospital admission rate than the 4 coldest months from November to February.

Contrary to our hypothesis, we found a statistically significant increase in the percentage of CHF visits admitted to the hospital during the warmer months. This suggests that although there are less ED CHF visits in the warmer months, a greater percentage tend to be severe.