Lipoprotein(a) and the risk of recurrent coronary heart disease: the Dubbo Study.

Objective: Elevated Lipoprotein(a) [Lp(a)] has not been firmly established as a risk factor for recurrent coronary heart disease (CHD). The present analysis explored this relationship in senior citizens.

Methods: This was a longitudinal study in 607 subjects, all with prevalent CHD, mean age 71 years, followed for 16 years. Baseline examinations of lipids and other CHD risk factors were conducted in 1988-89 in Dubbo, Australia. The independent contribution of Lp(a) to a further CHD event was examined in proportional hazards regression models.

Results: There were 399 incident CHD cases. Median Lp(a) in CHD cases was 130 mg/L (Interquartile range 60-315) and in non-cases 105 mg/L (45-250) ( < .07, U-Test). 26% of CHD cases and 19% of non-cases had Lp(a) 300 + mg/L; 18% of CHD cases and 8% of non-cases had Lp(a) 500 + mg/L. Lp(a) in Quintile 5 of its distribution (355 + mg/L), using Lp(a) Quintile 1 (<50mg/L) as reference, significantly predicted recurrent CHD with Hazard Ratio 1.53 (95% CI 1.11-2.11,  = .01). Prediction was independent of other risk factors. Lp(a) 500 + mg/L versus lower, significantly predicted recurrent CHD with Hazard Ratio 1.59 (1.16-2.17,  < .01). Prediction was similarly significant for Lp(a) 300 + mg/L versus lower, with Hazard Ratio 1.37 (1.09-1.73,  < .01).

Conclusion: Elevated Lp(a) is an independent and significant predictor of recurrent CHD in senior citizens. Upper reference Lp(a) levels of 500 mg/L (≈125nmol/L) or 300 mg/L (≈75nmol/L) both appear to be appropriate. The clinical benefit of therapy to reduce elevated Lp(a) remains to be confirmed.