Headache and the risk of stroke: a prospective observational cohort study among 35,056 Finnish men and women.

BACKGROUND Previous studies have shown an increased risk of stroke among patients with migraine. However, very few data are available on the possible association between chronic unspecified headache and the risk of stroke. METHODS A prospective cohort study including 35,056 randomly selected Finnish men and women aged 25 to 64 years at baseline who participated in a cardiovascular risk factor survey in 1972, 1977, 1982, or 1987. Self-reported headache, smoking, diabetes, blood pressure, weight, height, serum cholesterol level, and oral contraceptive use were recorded at baseline. During the follow-up, 2167 incident stroke events were ascertained with computer-based record linkage. RESULTS Women reported headache twice as often as men (16.7% vs 8.9%). Among men, the headache-associated hazard ratios (95% confidence intervals) for stroke were 4.08 (2.10-7.93), 1.86 (1.33-2.59), and 1.24 (1.05-1.47) during 1, 5, and a maximum of 23 years of follow-up, respectively. Adjustment for the other risk factors decreased the hazard ratios only slightly. Among women, there was also a direct but statistically nonsignificant association between headache and the risk of stroke. CONCLUSIONS Chronic headache is an independent predictor of stroke among men. Since the association between headache and the risk of stroke was particularly strong during a short follow-up, chronic headache may be a marker of the underlying disease process leading to acute stroke. The sex difference observed in this association may be due to a higher prevalence and a more heterogeneous etiology of headache in women compared with men.