A systematic comparison of the quality and volume of published data available on novel risk factors for stroke versus coronary heart disease.

BACKGROUND: To identify new treatments to prevent stroke, it is important that we have reliable data on potential novel risk factors. METHODS: We studied seven novel vascular risk factors [apo-lipoprotein (b), C-reactive protein, Chlamydia pneumoniae, fibrin-D dimer, fibrinogen, Helicobacter pylori and lipoprotein (a)] and compared the amount of published data on their relations with ischaemic stroke versus acute coronary events by systematic review of all studies published up to 2003. RESULTS: From a total of 22,875 abstracts reviewed, 266 eligible studies were identified (167 case-control studies and 99 cohort studies). Two hundred and eleven (79%) studies included coronary events as an outcome for the purpose of a risk factor analysis. In 186 (70%) studies, coronary events were the only outcome that was analysed. Only 73 (27%) studies included stroke or TIA as an outcome event, and only 45 studies (17%) reported risk factor analyses for ischaemic stroke separately. These results were qualitatively consistent across the risk factors studied and the relative lack of data on risk factors for stroke was even greater in prospective cohort studies. CONCLUSION: Data on novel risk factors for stroke are lacking compared with the equivalent data for acute coronary events, and there are very few data on specific subtypes of ischaemic stroke.