Anticardiolipin antibodies are not an independent risk factor for stroke: an incident case-referent study nested within the MONICA and Västerbotten cohort project.

BACKGROUND AND PURPOSE Anticardiolipin antibodies (aCL) have been proposed to be an independent risk factor for stroke. To test this hypothesis, a nested case-control study was performed to compare aCL with the other known risk factors for stroke. METHODS Within the framework of the World Health Organization Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) project and the Västerbotten Intervention Program (VIP) health survey, 44 725 men and women were enrolled and followed up from January 1, 1985, through August 31, 1996. Individuals free from cardiovascular events were followed up, and 123 developed stroke (on average, 34.1 months after blood sampling; 21 cerebral hemorrhage and 102 cerebral infarction); they were compared with 241 age- and sex-matched control subjects from the same population. ELISA was used for the analysis of IgG, IgM, and IgA aCL. RESULTS IgM-aCL were present in 11.4% of patients (14/123) who developed stroke and in 4. 1% of individuals (10/241) who remained healthy (P=0.013, OR 2.97, 95% CI 1.28 to 6.89). The OR for the levels of IgM-aCL was 1.34 (P=0. 01, 95% CI 1.07 to 1.68) without adjustment for other risk factors and 1.24 when adjusted for hypertension, diabetes mellitus, cigarette smoking, and use of smokeless tobacco (P=0.077, 95% CI 0. 98 to 1.56). There was no difference between patients and controls for the prevalence or level of IgG-aCL and IgA-aCL and also no difference between patients with cerebral hemorrhage and cerebral infarction for the prevalence of all 3 isotypes of aCL. CONCLUSIONS We conclude that aCL are associated with future stroke but do not constitute an independent risk factor.