BACKGROUND AND AIMS:High levels of lipoprotein(a) [Lp(a)] are associated with increased risk of acute coronary syndrome (ACS). We explored whether Lp(a) exhibits a stronger association with premature ACS. METHODS:A case-control study was conducted; 1457 patients with a history of ACS (54.8 ± 13 years, 86% males) and 2090 age-sex matched adults free of cardiovascular disease were enrolled. Bio-clinical characteristics [risk factors, low-density lipoprotein-cholesterol, Lp(a)] were derived through standard procedures. RESULTS:A 10 mg/dL increase in Lp(a) was associated with 4% (95% CI, 1.01 to 1.02) higher likelihood of having ACS in younger (<45 years) and 2% (95% CI, 1.01 to 1.02) higher likelihood in middle-aged (45-60 years) individuals. Adjusting for common risk factors, elevated Lp(a), i.e. >50 mg/dL, was still associated with increased likelihood of ACS in younger adults (<45 years) (OR = 2.88, 95% CI, 1.7 to 4.6) and in middle aged ones (45 and 60 years) (OR = 2.06, 95% CI, 1.4 to 3.2), but not in older participants (>60 years) (OR = 1.31, 95% CI, 0.8 to 2.4). CONCLUSIONS:Lp(a) seems to be an independent risk factor for ACS in individuals <45 years, and high Lp(a) levels increase by ∼3folds the risk for ACS. The association is preserved but is less in middle-aged individuals (45-60 years) and is abolished >60 years.