WESTPORT, Sep 15 (Reuters Health) - Despite mixed previous evidence, the results of a new study suggest a seasonal variation in stroke incidence.

In the study, strokes in general and ischemic strokes, but not hemorrhagic strokes, occurred most frequently in mid-May and least frequently in early December. The findings appear in the September 15th issue of American Journal of Epidemiology.

Even though some previous studies have indicated a seasonal variation in stroke incidence, the peak seasons have varied, Dr. Ronnie D. Horner of the VA Medical Center in Durham, North Carolina, and colleagues note.

In an attempt to resolve the controversy, Dr. Horner's team conducted a study of 72,779 veterans hospitalized for stroke during a 9-year period at 172 Veterans Affairs hospitals. This analysis showed "clear evidence of a seasonal pattern for stroke in general and for ischemic stroke in particular." For general stroke, the average peak was the week of May 13, and the average trough was the week of December 8.

The researchers evaluated race and climate region in relation to ischemic stroke incidence and found that neither factor appeared to have a strong effect on seasonal variation, according to the report.

Despite the evidence of a seasonal variation, "an explanation for the observed springtime peak in occurrence remains to be determined," the researchers writes.

(From ReutersHealth)