Does the incidence of headaches and migraines in the emergency department vary with day of week or month of year?

Study objectives: There is minimal literature on the epidemiology of patients with headache and migraine presenting to the emergency department (ED). Temporal variations may lead to insights into triggering mechanisms. Our goal is to determine whether there are differences in the incidence of ED visits for headache and migraine by day of week and month of year. Methods: We retrospectively analyzed data from a computerized billing database of ED visits. Fifteen New Jersey hospital EDs in urban and suburban areas with annual volumes of 20,000 to 68,000 were included. Participants were consecutive patients treated by emergency physicians from January 1, 1996, to August 31, 2003. Patients were included if the primary International Classification of Diseases diagnosis included headache or migraine. We calculated ED visits for headache and migraine as a percentage of total ED visits for each month of the year and day of the week. We compared these percentages to the average overall percentages for the entire period of the study, using the Student t test to determine statistical significance. We considered a P<.05 as statistically significant, with a Bonferroni adjustment to correct for multiple comparisons. Results: There were a total of 3,937,465 patients in the database, of whom 76,171 (1.9%) had a primary ED diagnosis of headache and 10,784 (0.27%) of migraine. For headaches, we found statistically significant differences by day of week and month of year. For the highest day, Wednesday, there was a proportional increase of 4% (95% confidence interval [CI] 2% to 7%; P<.001) compared with the overall average and for the lowest, Saturday, a decrease of 4% (95% CI 2% to 6%; P<.001). For the highest month, August, there was a proportional increase of 12% (95% CI 8% to 15%; P<.001), and for the lowest month, January, there was a decrease of 8% (95% CI 5% to 12%; P<.001). For migraine headaches, there were statistically significant differences only by day of week. Compared with the overall average, for the highest day, Sunday, there was a proportional increase of 11% (95% CI 4% to 18%; P<.001). Conclusion: Our study demonstrated statistically significant differences in the incidence of headache and migraines according to day of week and for headaches according to month of year. However, most of the differences were small. The only differences greater than 10% were for increased headache in August and increased migraine on Sunday.