Prospective cohort study of the association between use of low‐dose oral contraceptives and stroke in Chinese women

Purpose To clarify the association between use of widely distributed low-dose combined oral contraceptives (COCs) in China and the risk of stroke in order to decrease adverse reactions to COCs. Methods A prospective surveillance cohort study was undertaken in 25 towns in two counties in Jiangsu Province, China. Women (44 408 ) on hormonal contraceptives (HC) and 75 230 women with an intrauterine device (IUD) were followed up from July 1997 to June 2000 to study the difference in the incidence of stroke. Results The incidence of haemorrhagic stroke (age- and county-standardised rate) was far higher than that of ischaemic stroke (34.74 vs. 11.25 per 100 000 person years) among HC cohort. The relative risk (RR) of incidence of haemorrhagic stroke in the HC cohort (52 cases) was 2.72 times compared with that in the IUD cohort (23 cases). Compared with IUD users, the current users of HC had a higher RR of 4.20 (95%CI, 2.11–8.36) of haemorrhagic stroke, and still reached 2.17 (95%CI, 1.16–4.06) among past users after they stopped taking COCs for more than 10 years. The RR of haemorrhagic stroke was 3.09 (95%CI, 1.26–7.57) among women who had last used low-dose COCs during the previous 5 years. In women aged less than 45 years, compared to IUD users, the haemorrhagic stroke was strongly associated with current use of low-dose combined norethisterone pills, with RR being 19.06 (95%CI, 3.08–118.03). Conclusions There is an increased risk of haemorrhagic stroke among Chinese users of long-term low-dose oral contraceptives, which appears to persist long after discontinuation. Copyright © 2006 John Wiley & Sons, Ltd.