Monthly, weekly, and daily patterns in the incidence of congestive heart failure

To determine whether there are patterns in the incidence of emergency department (ED) visits for congestive heart failure (CHF) by month of the year, day of the week, or hour of the day.

This was a retrospective analysis of a computerized billing database of ED visits, involving seven northern New Jersey hospitals EDS: Consecutive patients seen by emergency physicians over an 11-year period (January 1, 1988--December 31, 1998) were included. Chi-square tests were used to evaluate for significant differences (p < 0.05).

There were a total of 2,370,233 patients in the database, of whom 26,224 had a primary ED diagnosis of CHF. The chi-square test rejected uniformity for month of the year, for day of the week, and for hour of the day (p < 0.0001). Visits for CHF were increased in the winter months. Compared with the average of the other months, December was the highest (14.3% above, p < 0.0001) and August was the lowest (15.5% below, p < 0.0001). There was also a day-of-the-week variation. Compared with the average of the other days, Monday was the highest (14.5% above, p < 0.0001) and Saturday was the lowest (9.6% below, p < 0.0001). There was also an hour-of-the-day pattern, with a rapid rise after 8 AM and a downtrend after 3 PM.

These data revealed a higher incidence of ED visits for CHF in the winter months, on Mondays, and during the hours of 8 AM to 3 PM. In comparison with previous studies, these data revealed a similar pattern by month of the year and a different pattern by hour of the day.