Increased risk for cardiovascular outcomes and effect of cholesterol-lowering pravastatin therapy in patients with diabetes mellitus in the pravastatin anti-atherosclerosis trial in the elderly (PATE)

Abstract

Background: The Pravastatin Anti-atherosclerosis Trial in the Elderly (PATE) was the first large-scale, prospective clinical trial to show that cholesterol-lowering therapy with pravastatin is effective in reducing the risk for cardiovascular events (CVEs) in elderly (aged ≥60 years) patients with hypercholesterolemia. PATE also included a subgroup of patients with diabetes mellitus (DM).

Objective: The aim of this post hoc analysis was to assess the effects of lon-gtermpravastatin therapy on cardiovascular outcomes in the subgroup of patients with DM compared with a subgroup without it.

Methods: PATE was conducted at 50 hospitals, universities, and clinics acrossJapan. Patients were randomly allocated to 1 of 2 treatment groups: low-dose pravastatin (5 mg PO QD; L group) or standard-lose pravastatin (in Japan, 10 mg PO QD; S group). Treatment was given for 3 to 5 years. Serum cholesterol levels were measured and the prevalence of CVEs was determined. The primary end point of the study was the S:L risk ratio for fatal or nonfatal CVEs. The secondary end point was the effect of diabetic patients' glycemic control on CVEs.

Results: A total of 665 patients (527 women, 138 men; mean [SD] age, 72.8[5.7] years) were followed up for a mean of 3.9 years (range, 3-5 years). Among these, 199 patients had DM; 104 patients with DM were allocated to the L group and 95 to the S group. Four hundred sixty-six patients did not have DM (L group, 230 patients; S group, 236 patients). Overall, between 3 months and 3 years after the initiation of treatment, patients in the L group (mean dose, 4.5 mg/d) experienced reductions from baseline total cholesterol level of 11% to 13%. Those in the S group (mean dose, 8.3 mg/d) experienced reductions from baseline of 15% to 17%. Decreases in low-density lipoprotein cholesterol (LDL-C) levels were 17% to 20% and 23% to 26% in the L and S groups, respectively. Statistically similar reductions were noted between patients with DM and those without it in response to either dose. The DM subgroup experienced 32 CVEs (L group, 17; S group, 15) compared with 39 CVEs (L group, 25; S group, 14) in the subgroup without DM. The S:L CVE risk ratio (primary end point) was 0.94 (95% Cl, 0.46-1.92) in patients with DM and 0.54 (95% Cl, 0.28-1.05) in those without DM; the differences between the treatment groups were not statistically significant. The risk for CVEs in patients with DM whose glycosylated hemoglobin concentrations were <8.0% and ≥8.0% were, respectively, 1.87-fold (95% Cl, 1.09-3.20; P = 0.02) and 3.79-fold (95% Cl, 1.92-7.48; P < 0.01) higher than that in patients without DM.

Conclusions: In this post hoc analysis of the effects of long-term cholesterol-loweringtherapy (low- and standard-dose pravastatin) on cardiovascular outcomes in elderly patients with DM, dose had no effect on the risk for CVEs in these patients as it did in those without DM. Poorer glycemic control in patients with DM was related to a higher risk for CVEs. The lack of pravastatin efficacy found in the subgroup with DM may have been attributable to the small differences in LDL-C levels found between the 2 treatment groups and/or the small sample size of the study.

Keywords: PATE study; diabetes mellitus; elderly patients; hyperlipidemia; pravastatin; prospective interventional trial.