Effects of Simvastatin on Augmentation Index Are Transient: Outcomes From a Randomized Controlled Trial

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

Association of statin therapy with progression of carotid arterial stiffness: the Multi-Ethnic Study of Atherosclerosis (MESA)

Arterial stiffness progresses with age and is a predictor of adverse cardiovascular disease events. Studies examining associations of statin therapy with arterial stiffness have yielded mixed results. Associations between the duration and intensity of statin therapy and arterial stiffness have not been studied in a prospective multiethnic cohort. MESA participants (n = 1242) with statin medication use data at each exam (1-5) and who had undergone B-mode carotid ultrasound at baseline and at Exam 5 after (mean ± [SD]) 9.4 ± 0.5 years were analyzed. Carotid arterial stiffness was measured using the distensibility coefficient (DC) and Young's elastic modulus (YEM). Linear regression models were used to evaluate associations between DC and YEM and statin treatment duration and intensity. At baseline, participants were 66.5 ± 8.1 years old, 41% female, 36% White, 30% African American, 14% Chinese American, and 20% Hispanic. The mean baseline low-density lipoprotein cholesterol (LDL-C) was 149.5 ± 14.5 mg/dL. After adjusting for age, sex, race/ethnicity, and CVD risk factors, the percent changes in DC and YEM were found to not be significantly different in individuals on statin therapy at any combination of visits (1-4) compared to participants never on statin therapy (all p > 0.32). There were also no differences in the percent change in DC and YEM based on statin therapy intensity by quartile (all p > 0.14) over the 10-year follow-up period. Based on the aforementioned results, statin therapy was not associated with changes in carotid artery stiffness over nearly a decade of follow-up regardless of therapy duration or intensity.

Carotid Artery Stiffening With Aging: Structural Versus Load-Dependent Mechanisms in MESA (the Multi-Ethnic Study of Atherosclerosis)

Elastic arteries stiffen via 2 main mechanisms: (1) load-dependent stiffening from higher blood pressure and (2) structural stiffening due to changes in the vessel wall. Differentiating these closely coupled mechanisms is important to understanding vascular aging. MESA (Multi-Ethnic Study of Atherosclerosis) participants with B-mode carotid ultrasound and brachial blood pressure at exam 1 and exam 5 (year 10) were included in this study (n=2604). Peterson and Young elastic moduli were calculated to represent total stiffness. Structural stiffness was calculated by adjusting Peterson and Young elastic moduli to a standard blood pressure of 120/80 mm Hg with participant-specific models. Load-dependent stiffness was the difference between total and structural stiffness. Changes in carotid artery stiffness mechanisms over 10 years were compared by age groups with ANCOVA models adjusted for baseline cardiovascular disease risk factors. The 75- to 84-year age group had the greatest change in total, structural, and load-dependent stiffening compared with younger groups (P<0.05). Only age and cessation of antihypertensive medication were predictive of structural stiffening, whereas age, race/ethnicity, education, blood pressure, cholesterol, and antihypertensive medication were predictive of increased load-dependent stiffening. On average, structural stiffening accounted for the vast majority of total stiffening, but 37% of participants had more load-dependent than structural stiffening. Rates of structural and load-dependent carotid artery stiffening increased with age. Structural stiffening was consistently observed, and load-dependent stiffening was highly variable. Heterogeneity in arterial stiffening mechanisms with aging may influence cardiovascular disease development.

Effects of simvastatin on white matter integrity in healthy middle-aged adults

Background

The brain is the most cholesterol‐rich organ and myelin contains 70% of total brain cholesterol. Statins are potent cholesterol‐lowing medications used by millions of adults for prevention of vascular disease, yet the effect of statins on cholesterol‐rich brain white matter (WM) is largely unknown.

Methods

We used longitudinal neuroimaging data acquired from 73 healthy, cognitively unimpaired, statin‐naïve, middle‐aged adults during an 18‐month randomized controlled trial of simvastatin 40 mg daily (n = 35) or matching placebo (n = 38). ANCOVA models (covariates: age, sex, APOE‐ɛ4) tested the effect of treatment group on percent change in WM, gray matter (GM), and WM hyperintensity (WMH) neuroimaging measures at each study visit. Mediation analysis tested the indirect effects of simvastatin on WM microstructure through change in serum total cholesterol levels.

Results

At 18 months, the simvastatin group showed a significant preservation in global WM fractional anisotropy (β = 0.88%, 95% CI 0.27 to 1.50, P = 0.005), radial diffusivity (β = −1.10%, 95% CI −2.13 to −0.06, P = 0.039), and WM volume (β = 0.72%, 95% CI 0.13 to 1.32, P = 0.018) relative to the placebo group. There was no significant effect of simvastatin on GM or WMH volume. Change in serum total cholesterol mediated approximately 30% of the effect of simvastatin on WM microstructure.

Conclusions

Simvastatin treatment in healthy, middle‐aged adults resulted in preserved WM microstructure and volume at 18 months. The partial mediation by serum cholesterol reduction suggests both peripheral and central mechanisms. Future studies are needed to determine whether these effects persist and translate to cognitive outcomes.

Trial Registration

NCT00939822 (ClinicalTrials.gov).

Measurement batch differences and between-batch conversion of Alzheimer's disease cerebrospinal fluid biomarker values

INTRODUCTION

Batch differences in cerebrospinal fluid (CSF) biomarker measurement can introduce bias into analyses for Alzheimer's disease studies. We evaluated and adjusted for batch differences using statistical methods.

METHODS

A total of 792 CSF samples from 528 participants were assayed in three batches for 12 biomarkers and 3 biomarker ratios. Batch differences were assessed using Bland-Altman plot, paired t test, Pitman-Morgan test, and linear regression. Generalized linear models were applied to convert CSF values between batches.

RESULTS

We found statistically significant batch differences for all biomarkers and ratios, except that neurofilament light was comparable between batches 1 and 2. The conversion models generally had high R 2 except for converting P-tau between batches 1 and 3.

DISCUSSION

Between-batch conversion allows harmonized CSF values to be used in the same analysis. Such method may be applied to adjust for other sources of variability in measuring CSF or other types of biomarkers.

Beneficial Effect of Statin Therapy on Arterial Stiffness

Arterial stiffness describes the increased rigidity of the arterial wall that occurs as a consequence of biological aging and several diseases. Numerous studies have demonstrated that parameters to assess arterial stiffness, especially pulse-wave velocity, are predictive of those individuals that will suffer cardiovascular morbidity and mortality. Statin therapy may be a pharmacological strategy to improve arterial elasticity. It has been shown that the positive benefits of statin therapy on cardiovascular disease is attributable not only to their lipid-lowering capacity but also to various pleiotropic effects, such as their anti-inflammatory, antiproliferative, antioxidant, and antithrombotic properties. Additionally, statins reduce endothelial dysfunction, improve vascular and myocardial remodeling, and stabilize atherosclerotic plaque. The aim of the present review was to summarize the evidence from human studies showing the effects of statins on arterial stiffness.

Review of the Protective Effects of Statins on Cognition

Elevated cholesterol is a major risk factor in the development of cardiovascular disease. Statins have proven to be effective in lowering low-density lipoprotein cholesterol as well as the incidence of cardiovascular events. As a result, statins are widely prescribed in the United States, with an estimated 35 million patients on statins. Many of these patients are older than age 65 and suffer from various comorbidities, including mild to severe cognitive impairment. Early studies looking at the effects of statins on cognition have shown that statin use may lead to mild reversible cognitive decline, although long-term studies have shown inconclusive findings. In recent years, studies have shown that the use of statins in certain groups of patients may lead to a reduction in the rate of cognitive decline. One hypothesis for this finding is that statin use can reduce the risk of cerebrovascular disease which may, in turn, reduce the risk of mild cognitive decline and dementia. With numerous patients currently prescribed statins and the likelihood that more patients will be prescribed the medication in the coming years, it is important to review the current literature to determine the association between statin use and cognitive decline, as well as determine how statins may be beneficial in preventing cognitive decline.

Effects of Simvastatin on Augmentation Index Are Transient: Outcomes From a Randomized Controlled Trial

Background

Statins improve endothelial function, but their effects on arterial stiffness and aortic blood pressure in middle‐aged adults are uncertain.

Methods and Results

This was a prospective, randomized, double‐blind, placebo‐controlled trial of middle‐aged (40‐72 years old) adults who were randomly assigned to receive simvastatin 40 mg (n=44) or placebo (n=44) daily for 18 months to evaluate impact on dementia‐related biomarkers (primary end points) and measures of vascular health (secondary end points). This analysis focuses on the predetermined secondary end points of changes in central aortic blood pressure, aortic augmentation index, and brachial artery flow‐mediated dilation. Measurements were performed at baseline and after 6, 12, and 18 months. Multivariable models were used to identify predictors of these prespecified vascular end points. Study groups were similar at baseline; low‐density lipoprotein cholesterol declined in the statin group but not in the placebo group (P<0.01). There were no significant differences in changes in central blood pressure parameters or flow‐mediated dilation (all P>0.2). After 12 months, augmentation index decreased from baseline in the statin group compared with the placebo group (−2.3% [5.5%] versus 1.2% [5.7%], P=0.007), but by 18 months the response in both groups trend toward baseline (−1.1% [5.8%] versus 0.2% [4.8%], P=0.3). Low‐density lipoprotein cholesterol was not associated with changes in augmentation index at any time point.

Conclusions

Statin therapy led to a short‐term reduction in augmentation index after 12 months, but this effect did not persist after 18 months despite continued reduction in low‐density lipoprotein cholesterol levels. These findings suggest that statins may have a transient effect on aortic stiffness.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT00939822.