Seasonal variation in the incidence of aneurysmal subarachnoid hemorrhage associated with age and gender: 20-year results from the Yamaguchi cerebral aneurysm registry.

BACKGROUND

This study was a cerebral aneurysm registry study conducted in a region with few climatic differences. Based on data collected for over 20 years, seasonal variations and characteristics of subarachnoid hemorrhage (SAH) due to ruptured aneurysms were analyzed.

METHODS

This study included 5,007 patients in the Yamaguchi Prefecture with aneurysmal SAH between 1986 and 2005. Incidence rates by month, sex, age, severity, and aneurysm site were analyzed.

RESULTS

In women, seasonal variation was observed, in particular among those aged ≥50 years. Among those aged 50-69 years, the highest incidence was in October, and the nadir was in June (peak-to-trough ratio = 1.72). At age ≥70 years, this was slightly different, with the highest incidence in December and the nadir in July (peak-to-trough ratio = 1.48). However, there was no seasonal variation in men overall; it was limited to elderly men at age ≥70 years, with the highest incidence in January and the nadir in July (peak-to-trough ratio = 2.9). Aneurysm site and severity showed no relationship with seasonal variation.

CONCLUSION

The present study shows seasonal variations in the onset of SAH. Seasonal variations in SAH differed depending on age and sex.