Short- and long-term association of lipid-lowering drug treatment and cardiovascular disease by estimated absolute risk in the Second Australian National Blood Pressure study

Abstract

Background: There is currently insufficient evidence to support the use of lipid-lowering drug treatment (LLT) for primary prevention of cardiovascular disease (CVD) in the elderly. Objectives: We examined the relationship of early initiation of LLT with short- and long-term all-cause and CVD mortality in persons older than 65 years in this post hoc study from the Second Australian National Blood Pressure study (ANBP2). Methods: This was an in- and post-trial observational study. About 4257 hypertensive participants aged 65 to 84 years within Australian family practices were randomized to an angiotensin-converting enzyme inhibitor or a diuretic treatment group. After excluding participants with a prior history of CVD, the cohort was stratified into “LLT” and “no LLT” subgroups based on LLT status at randomization. Results: At randomization, the participants had a mean age of 72 years, average blood pressure of 168/91 mm Hg and estimated 5-year CVD risk of 18.7 ± 8.3%. In the overall study population, the association of LLT with long-term (11-years) all-cause and non-CVD mortality was significant (hazard ratio [HR] 0.78 [95% confidence interval {CI} 0.66–0.92, P =.003] and HR 0.70 [95% CI 0.54–0.90, P =.006], respectively). Magnitudes of the association of LLT with long-term mortality and the association with short-term mortality were similar; however, no statistically significant association with short-term mortality was observed. In the subgroup analysis by baseline 5-year CVD risk, LLT participants in the highest risk tertile had a substantially lower relative risk for short-term all-cause mortality (HR 0.31, 95% CI 0.13–0.71, P for interaction.02) compared to those with lower estimated CVD risk. All analyses were adjusted for baseline and in-trial characteristics. Conclusion: Our study showed a strong association between LLT and reduced long-term all-cause mortality. Thus, our findings support recommendations of the use of LLT in patients over 65 years, particularly those with high CVD risk who were more likely to obtain additional benefits in the short term. The findings also suggested that mortality benefits of LLT for the elderly may take longer to become evident.