Background: The enzyme in matrix metalloproteinase (MMP)-9 has been suggested to be an important determinant of plaque degradation. While several studies have shown elevated levels in patients with coronary heart disease, results in prospective population based studies evaluating MMP-9 in relation to first time coronary events have been inconclusive. As of today, there are four published studies which have measured MMP-9 in serum and none using plasma. Measures of MMP-9 in serum have been suggested to have more flaws than measures in plasma.
Aim: To investigate the independent association between plasma levels of MMP-9 and first-time incidence of coronary events in an 8-year follow-up.
Material and methods: 428 men and 438 women, aged 45-69 years, free of previous coronary events and stroke at baseline, were followed-up. Adjustments were made for sex, age, socioeconomic position, behavioral and cardiovascular risk factors, chronic disease at baseline, depressive symptoms, interleukin-6 and C-reactive protein.
Results: 53 events were identified during a risk-time of 6 607 person years. Hazard ratio (HR) for MMP-9 after adjustment for all covariates were HR = 1.44 (1.03 to 2.02, p = 0.033). Overall, the effect of adjustments for other cardiovascular risk factors was low.
Conclusion: Levels of plasma MMP-9 are independently associated with risk of first-time CHD events, regardless of adjustments. These results are in contrast to previous prospective population-based studies based on MMP-9 in serum. It is essential that more studies look at MMP-9 levels in plasma to further evaluate the association with first coronary events.