Authors' objectives:

To conduct a systematic review of published scientific literature on the effects of interventions for primary prevention of cardiovascular disease. This was to be used as background material for the development of national clinical practice guidelines in this area.

Authors' recommendations: The effect-studies we found that fulfilled our criteria for inclusion were mainly about medication. The quality of the evidence varied considerably. The results indicate that aspirin may reduce the risk of myocardial infarction (22% relative risk-reduction, 95% CI: 3% to 38%) and death (6% relative risk-reduction, 95% CI 0% to 13%). The effect regarding myocardial infarction seems to relate only to men. However, the results also seem to indicate that aspirin protects women, but not men, against stroke (18% relative risk-reduction, 95% CI 4% to 30% among women). The effect of warfarin, or the combination of aspirin and warfarin, has only been evaluated in one study, where only men participated. The results indicate similar effect-sizes as for aspirin alone. The use of anti-thrombotic medication is associated with an increased risk of bleeding, also at low dosages. Treatment with statins reduces the risk of myocardial infarction (23% relative risk-reduction, 95% CI 18% to 28%). The incidence of stroke also seems to be lower among those who receive these drugs (relative risk-reduction 17%, 95% CI 10% to 24%). This is also the case in regard to total mortality although these findings are less convincing (relative risk-reduction 7%, 95% CI 1% to 14%). For lipid-lowering drugs other than statins the results are less clear, but also these drugs seem to reduce the risk of myocardial infarction (relative risk-reduction 16%, 95% CI 6% to 26%). Antihypertensive medication reduces the risk of stroke (relative risk-reduction 40%, 95% CI 33% to 46%), myocardial infarction (relative risk-reduction 15%, 95% CI 6% to 23%), development of heart failure (relative risk-reduction 48%, 95% CI 37% to 57%), and death (relative risk-reduction 11%, 95% CI 5% to 16%). Concerning comparisons between different types of drugs or drug combinations, there was no obvious winner. For most comparisons we did not find clear differences, indicating that the most important issue is to reduce blood-pressure per se. In some cases one drug performed somewhat better with regards to one outcome while the other drug performed better for another. Beta-blockers and alpha-blockers were not the statistically significant best agent in any comparison, and the evidence in support of these drug classes can therefore be considered weaker than for the others. The results from the sub-group of diabetes patients largely overlapped with the main findings from these studies. With regards to the use of antihypertensives as supplementary medication for persons with diabetes, regardless of whether the patient has hypertension or not, the evidence indicates that this has little or no effect on total mortality, risk of stroke or heart failure, but that it may reduce the risk of myocardial infarction (14% relative risk-reduction, 95% CI 1% to 25%) and the risk of developing renal failure (17% relative risk-reduction, 95% CI 4% to 28). We have not found clear evidence that specific antihypertensive drugs stand out as better than others for diabetes patients. The results from one study of sylphonylurea did not show a clear effect on the incidence of cardiovascular disease. Based on the findings from one study, metformin may have an effect on total mortality (relative risk-reduction 32%, 95% CI 7% to 51%) and risk of myocardial infarction (relative risk-reduction 36%, 95% CI 8% to 55%). It seems likely, based on the results from a single study of persons with impaired glucose tolerance, that acarbose has an effect on the risk of myocardial infarction (relative risk-reduction 92%, 95% CI 36% to 99%). Although the difference was not statistically significant (p>0,05) for most outcomes, the results from the two rosiglitazone-studies we have included provide reason to suspect that the risk of cardiovascular disease increases with the use of this drug. The results from the studies we have found do not provide a clear answer as to whether, or to what extent, multifactorial interventions are effective for reducing cardiovascular risk. The findings from one study indicate that omega-3 fatty acid (EPA) is not effective with regards to total mortality or risk of stroke, but may be protective against myocardial infarction (22% relative risk-reduction, 95% CI -3% to 41%). Based on the findings from one study, E-vitamin seems to have no effect with regards to preventing cardiovascular disease.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.nokc.no

Year Published: 2008

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Norway

Organisation Name: Norwegian Institute of Public Health

Contact Address: Universitetsgata 2, Postbox 7004 St. Olavs plass, NO-0310 Oslo NORWAY. Tel: +47 23 25 50 00; Fax: +47 23 25 50 10;

Contact Name: Berit.Morland@nokc.no, dagny.fredheim@nokc.no

Contact Email: Berit.Morland@nokc.no, dagny.fredheim@nokc.no

Copyright: Norwegian Knowledge Centre for the Health Services (NOKC)