Triglyceride as a risk factor for ischaemic heart disease in British men: effect of adjusting for measurement error

Objective: To assess the influence of differential precision in the measure ment of the correlated variables total cholesterol and high density lipopro tein (HDL) cholesterol on the estimates of the risk of ischaemic heart dise ase (IHD) associated with plasma triglyceride levels. Design, setting and p articipants: The Caerphilly Heart Disease Study (CHDS), a prospective cohor t study of 2512 middle-aged men living in the town of Caerphilly, south Wal es, UK, The results from two sub-studies were used to estimate the degree o f measurement imprecision (laboratory error and within-person variation) in triglycerides, total cholesterol and HDL cholesterol. Main outcome measure s: Multivariable risk estimates for major IHD calculated from logistic regr ession analysis, adjusted and not adjusted for measurement imprecision. Maj or IHD events were defined as death from IHD, clinical non-fatal myocardial infarction or electrocardiographic myocardial infarction. Results: There w ere 261 men with major IHD events during follow-up. In age-adjusted analyse s, taking measurement imprecision into account strengthened associations wi th IHD for all lipid factors. The odds ratio (OR) for one S.D. increase in triglycerides, ignoring measurement imprecision, was 1.36 (95% confidence i nterval [95% CT] 1.20-1.55) but 1.57 (95% CI 1.30-1.89) when taking impreci sion into account. The standardised odds ratio for triglycerides adjusted f or measurement imprecision and the two other lipid factors was 1.35 (95% CI 1.09-1.69). In this model, the triglyceride level showed a stronger associ ation than total cholesterol (OR 1.28; 95% CI 1.05-1.56) and HDL cholestero l (OR for one S.D. decrease 1.20; 95% CI 0.97-1.49). When adding fasting bl ood glucose and diastolic blood pressure, however, the effect of triglyceri des was reduced and ceased to be statistically significant (OR 1.19; 95% CI 0.95-1.49). This was further attenuated upon inclusion of body mass index, smoking status and history of pre-existing IHD. Total cholesterol remained a statistically significant (P < 0.05) risk factor in all models. Conclusi ons: In contrast to other cohort studies, triglyceride concentration in the CHDS shows an association with the risk of IHD which is independent of tot al and HDL cholesterol. This effect was pronounced after adjustment for mea surement imprecision. It was reduced, however, when adjusted for other fact ors. While hypertriglyceridaemia may exert an influence independent of othe r lipid factors, insulin resistance is probably the underlying metabolic di sturbance. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.