Effects of past and recent blood pressure and cholesterol level on coronary heart disease and stroke mortality, accounting for measurement error.

The authors aimed to quantify the effects of current systolic blood pressure (SBP) and serum total cholesterol on the risk of mortality in comparison with SBP or serum cholesterol 25 years previously, taking measurement error into account. The authors reanalyzed 35-year follow-up data on mortality due to coronary heart disease and stroke among subjects aged 65 years or more from nine cohorts of the Seven Countries Study. The two-step method of Tsiatis et al. (J Am Stat Assoc 1995;90:27-37) was used to adjust for regression dilution bias, and results were compared with those obtained using more commonly applied methods of adjustment for regression dilution bias. It was found that the commonly used univariate adjustment for regression dilution bias overestimates the effects of both SBP and cholesterol compared with multivariate methods. Also, the two-step method makes better use of the information available, resulting in smaller confidence intervals. Results comparing recent and past exposure indicated that past SBP is more important than recent SBP in terms of its effect on coronary heart disease mortality, while both recent and past values seem to be important for effects of cholesterol on coronary heart disease mortality and effects of SBP on stroke mortality. Associations between serum cholesterol concentration and risk of stroke mortality are weak.