Associations between apolipoprotein B, apolipoprotein AI, the apolipoprotein B/AI ratio and coronary heart disease: a literature-based meta-analysis of prospective studies

Objectives. To assess associations of circulating levels of apolipoprotein (apo) AI, apoB and the apoB/AI ratio (apoB/A) with risk of incident coronary heart disease (CHD). Design. Literature-based meta-analysis of prospective studies. Data soueces. Prospective studies in essentially general populations that reported on associations between apoAI, apoB or apoB/A and first incident CHD outcomes. Studies were identified by computer-based searches and by manual searches of the relevant literature. Results. Data from 23 relevant studies were identified. For apoAI, with 6333 CHD cases in 21 studies, comparison of individuals in the bottom third with those in the top third of baseline values yielded a combined relative risk of 1.62 (95% confidence interval: 1.43-1.83), i.e. an inverse association. For apoB, a combined analysis of 6320 CHD cases from 19 studies gave a relative risk of 1.99 (1.65-2.39) for a comparison of individuals in the top third versus those in the bottom third of baseline values. For apoB/A, with 3730 CHD cases from seven studies, a comparison of individuals in the top third versus the bottom third of baseline values gave a combined relative risk of 1.86 (1.55-2.22). These associations were somewhat stronger following correction for within-person variations in apolipoprotein levels. There was evidence of heterogeneity amongst the published studies, but it was only partly explained by available study-level characteristics. Conclusion. The present quantitative review suggests the existence of moderately strong associations between baseline levels of each of apoAI, apoB, and apoB/A and risk of CHD. More detailed analysis, perhaps based on individual participant data from prospective studies, could help to overcome several limitations in the present review and to clarify any relevance of these apolipoproteins to disease prediction and aetiology.