Increasing incidence of stroke among Swedish women.

The incidence of stroke and transient ischemic attack was studied prospectively in the municipality of Söderhamn, Sweden, during the periods 1975-1978 and 1983-1986. A total of 723 cases of stroke and 111 cases of transient ischemic attack were registered during the two periods. The number of first-ever strokes increased by 28% between the 1970s and the 1980s, while the annual incidence of first-ever stroke rose from 2.90 to 3.53/1,000 (p less than 0.02). Female incidence increased by 38%, from 2.62 to 3.62/1,000 (p less than 0.05) between the study periods. Male incidence, however, changed nonsignificantly from 3.19 in the first period to 3.43 in the second. In 1975-1978, male incidence was four times greater than that of females up to 65 years of age, but the distribution became balanced in 1983-1986, when the increment of female incidence was 47% in the group 25-44 years old and 232% (p less than 0.05) in the group 45-64 years old. The annual incidence of first-ever transient ischemic attack was 0.43/1,000 in men and 0.48/1,000 in women in 1975-1978. The corresponding rates for 1983-1986 were 0.56 and 0.45/1,000, respectively. These changes were not significant. The cause of the increase in the incidence of stroke among women has not been established.