Influences of age, sex, and LDL-C change on cardiovascular risk reduction with pravastatin treatment in elderly Japanese patients: A post hoc analysis of data from the Pravastatin Anti-atherosclerosis Trial in the Elderly (PATE)

Abstract

Background: The Pravastatin Anti-atherosclerosis Trial in the Elderly (PATE) found that the prevalence of cardiovascular events (CVEs) was significantly lower with standard-dose (10-20 mg/d) pravastatin treatment compared with low-dose (5 mg/d) pravastatin treatment in elderly (aged ⩾ 60 years) Japanese patients with hypercholesterolemia. Small differences in on-treatment total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels between the 2 dose groups in the PATE study were associated with significant differences in CVE prevalence. However, the reasons for these differences have not been determined. How sex and age differences influence the effectiveness of pravastatin also remains unclear.

Objectives: The aims of this study were to determine the relationship between reduction in LDL-C level and CVE risk reduction in the PATE study and to assess the effects of sex and age on the effectiveness of pravastatin treatment (assessed using CVE risk reduction).

Methods: In this post hoc analysis, Cox regression analysis was performed to study the relationship between on-treatment (pravastatin 5-20 mg/d) LDL-C level and CVE risk reduction using age, sex, smoking status, presence of diabetes mellitus and/or hypertension, history of cardiovascular disease (CVD), and high-density lipoprotein cholesterol level as adjustment factors. To explore risk reduction due to unspecified mechanisms other than LDLrC reduction, an estimated Kaplan-Meier curve from the Cox regression analysis was calculated and compared with the empirical (observed) Kaplan-Meier curve.

Results: A total of 665 patients (527 women, 138 men; mean [SD] age, 72.8 [5.7] years) were enrolled in PATE and were followed up for a mean of 3.9 years (range, 3-5 years). Of those patients, 50 men and 173 women were ⩾75 years of age. Data from 619 patients were included in the present analysis. In the calculation of model-based Kaplan-Meier curves, data from an additional 32 patients were excluded from the LDL-C analysis because there were no data on pretreatment LDL levels; hence, the data from 587 patients were analyzed. A reduction in LDL-C level of 20 mg/dL was associated with an estimated CVE risk reduction of 24.7% (hazard ratio [HR] = 0.753; 95% CI, 0.625-0.907; P = 0.003). Risk was reduced by 22.2% in patients aged <75 years (HR = 0.778; 95% CI, 0.598-1.013; P = NS) and 29.9% in patients aged ⩾75 years (HR = 0.701; 95% CI, 0.526-0.934; P = 0.015). The risk reductions were 19.8% in women (HR = 0.802; 95% CI, 0.645-0.996; P = 0.046) and 35.8% in men (HR = 0.642; 95% CI, 0.453-0.911; P = 0.013). The risk reduction was 32.4% in patients without a history of CVD at enrollment (HR = 0.676; 95% CI, 0.525-0.870; P = 0.002) and 15.1% in those with a history of CVD (HR = 0.849; 95% CI, 0.630-1.143; P= NS). The estimated Kaplan-Meier curve strongly suggested that the effects of pravastatin were only partially associated with changes in LDLrC level.

Conclusions: The results from this post hoc analysis suggest that pravastatin 5 to 20 mg/d might elicit CVE risk reduction by mechanisms other than cholesterol-lowering effects alone. They also suggest that pravastatin treatment might be effective in reducing the risk for CVEs in both female and male patients aged ⩾75 years.

Keywords: PATE study; PROBE trial; elderly; hypercholesterolemia; post hoc; pravastatin.