Long-term moderately elevated LDL-cholesterol and blood pressure and risk of coronary heart disease

Background Harmful effects of long-term exposure to moderately elevated low-density lipoprotein (LDL)cholesterol and blood pressure on coronary heart disease (CHD) have not been rigorously examined. We estimated the risk of CHD under long-term exposure to moderately elevated LDL-cholesterol and blood pressure compared with the risk under shorter exposures to higher levels of the same risk factors. Methods Observational study using data from 2,714 adults in Framingham Offspring Study who were free of existing cardiovascular disease and aged <70 years at baseline (1987 +/- 1991). We used the parametric g-formula to estimate 16-year CHD risk under different levels and durations of exposure to LDL-cholesterol (low: < 130 mg/dL, moderate: 130 to < 160 mg/dL, high 160 to < 190 mg/dL, and very high: >= 190 mg/dL) and systolic blood pressure (low: < 120 mmHg, prehypertension: 120 to < 140 mmHg, stage 1 hypertension: 140 to < 160 mmHg, and stage 2 hypertension: >= 160 mmHg). Results The estimated 16-year CHD risk under exposure to low LDL was 8.2% (95% CI = 7.0 +/- 9.6). The 16-year CHD risk under exposure to moderate LDL was 8.9% (7.8 +/- 10.1) which was similar to CHD risk under 8 years of low LDL followed by 8 years of high LDL at 9.0% (7.7 +/- 10.3); and 12 years of low LDL followed by 4 years of very high LDL at 8.8% (7.6 +/- 10.1). The results for blood pressure were similar. Conclusions Long-term exposure to moderate levels of LDL-cholesterol and blood pressure had a similar impact on CHD risk as shorter exposures to levels considered 'high' per clinical guidelines.