Background: Several studies have observed high plasma levels of homocysteine among patients with coronary heart disease (CHD). The only prospective study was based on US physicians, and concluded that homocysteine was associated with subsequent myocardial infarction (MI). However, the association was limited to those above a threshold level of homocysteine.
Methods: We conducted a nested case-control study among the 21,826 subjects, aged 12-61 years, who were surveyed in the municipality of Tromsø, Norway. Among those free from MI at the screening, 123 later developed CHD. Four controls were selected for each case.
Results: Level of homocysteine was higher in cases than in controls (12.7 +/- 4.7 versus 11.3 +/- 3.7 mumol/l (mean +/- SD); P = 0.002). The relative risk for a 4 mumol/l increase in serum homocysteine was 1.41 (95% confidence interval (CI): 1.16-1.71). Adjusting for possible confounders reduced the relative risk to 1.32 (95% CI: 1.05-1.65). There was no threshold level above which serum homocysteine is associated with CHD events.
Conclusions: In the general population serum total homocysteine is an independent risk factor for CHD with no threshold level.