1996 Remington lecture: modeling multivariate longitudinal data that are incomplete

Resveratrol and exercise to treat functional limitations in late life: design of a randomized controlled trial

Skeletal muscle mitochondrial function declines with age and is a key factor in the maintenance of physical function among older adults. Research studies from animals and humans have consistently demonstrated that exercise improves skeletal muscle mitochondrial function in early and middle adulthood. However, mitochondrial adaptations to both acute and chronic exercise are attenuated in late life. Thus, there is an important need to identify adjuvant therapies capable of augmenting mitochondrial adaptations to exercise (e.g. improved mitochondrial respiration, muscle mitochondria biogenesis) among older adults. This study is investigating the potential of resveratrol supplementation for this purpose. The objective of this randomized, double-masked pilot trial is to evaluate the efficacy of resveratrol supplementation combined with a comprehensive supervised exercise program exercise for improving physical function among older adults. Moderately functioning, sedentary participants aged ≥60 years will perform 24 sessions (2 day/wk for 12 weeks) of center-based walking and resistance training and are randomly assigned to receive either (1) 500 mg/day resveratrol (2) 1000 mg/day resveratrol or (3) placebo. Study dependent outcomes include changes in 1) knee extensor strength, 2) objective measures of physical function (e.g. 4m walk test, Short Physical Performance Battery), 3) subjective measures of physical function assessed by Late Life Function and Disability Instrument, and 4) skeletal muscle mitochondrial function. This study will provide novel information regarding the therapeutic potential of resveratrol supplementation combined with exercise while also informing about the long-term clinical viability of the intervention by evaluating participant safety and willingness to engage in the intervention.

Wearable technology to reduce sedentary behavior and CVD risk in older adults: design of a randomized controlled trial

Persons aged over 65 years account for over the vast majority of healthcare expenditures and deaths attributable to cardiovascular disease (CVD). Accordingly, reducing CVD risk among older adults is an important public health priority. Structured physical activity (i.e. exercise) is a well-documented method of decreasing CVD risk, but recent large-scale trials suggest that exercise alone is insufficient to reduce CVD events in high-risk populations of older adults. Thus adjuvant strategies appear necessary to reduce CVD risk. Accumulating evidence indicates that prolonged sedentary behavior (e.g. sitting) has detrimental health effects that are independent of engagement in recommended levels of moderate-intensity exercise. Yet clinical trials in this area are lacking. We hypothesize that exercise, when combined with a novel technology based intervention specifically designed to reduce sedentary behavior will reduce CVD risk among sedentary older adults. The purpose of this study is to evaluate the feasibility and efficacy of combining a traditional, structured exercise intervention with an innovative intervention designed to decrease sedentary behavior and increase non-exercise physical activity (NEPA). This study will provide us with critical data necessary to design and implement a full-scale trial to test our central hypothesis. Participants aged ≥60 years with moderate to high risk of coronary heart disease (CHD) events are randomly assigned to either the exercise and technology intervention (EX+NEPA) or exercise alone (EX) groups. Study dependent outcomes include changes in 1) daily activity patterns, 2) blood pressure, 3) exercise capacity, 4) waist circumference, and 5) circulating indices of cardiovascular function. This study will provide critical information for designing a fully-powered clinical trial, which could have health implications for the ever increasing population of older adults.

Carotid intima-media thickness studies: study design and data analysis

BACKGROUND

Carotid intima-media thickness (CIMT) measurements have been widely used as primary endpoint in studies into the effects of new interventions as alternative for cardiovascular morbidity and mortality. There are no accepted standards on the use of CIMT measurements in intervention studies and choices in the design and analysis of a CIMT study are generally based on experience and expert opinion. In the present review, we provide an overview of the current evidence on several aspects in the design and analysis of a CIMT study on the early effects of new interventions.

SUMMARY OF ISSUES

A balanced evaluation of the carotid segments, carotid walls, and image view to be used as CIMT study endpoint; the reading method (manual or semi-automated and continuously or in batch) to be employed, the required sample size, and the frequency of ultrasound examinations is provided. We also discuss the preferred methods to analyse longitudinal CIMT data and address the possible impact of, and methods to deal with missing and biologically implausible CIMT values.

CONCLUSIONS

Linear mixed effects models are the preferred way to analyse CIMT data and do appropriately handle missing and biologically implausible CIMT values. Furthermore, we recommend to use extensive CIMT designs that measure CIMT at regular points during the multiple carotid sites as such approach is likely to increase the success rates of CIMT intervention studies designed to evaluate the effects of new interventions on atherosclerotic burden.

Results From a Carotid Intima-Media Thickness Trial as a Decision Tool for Launching a Large-Scale Morbidity and Mortality Trial

Background—

Trials with carotid intima-media thickness (CIMT) as primary end point may improve the efficiency of the evaluation of new therapies targeting atherosclerosis considerably, and the results of CIMT trials may be used as a decision tool to help in the choice to launch or not to launch a large-scale morbidity and mortality (M&M) trial. We evaluated the literature to provide evidence to support or refute this proposition.

Methods and Results—

PubMed Medline was systematically searched on May 1, 2012, for randomized double-blind controlled CIMT trials. The agreement between the results from CIMT and M&M trials was assessed, and positive and negative predictive values were calculated. Forty-eight CIMT trials were included. CIMT trials (n=20) on lipid-level modifying therapies are all, except one, in agreement with the M&M trial findings. For blood pressure-lowering trials (n=13), 3 were not congruent with the M&M trial. The positive and negative predictive value (95% confidence interval) of a CIMT trial to predict the outcome of a M&M trial are 96% (80–99%) and 83% (64–93%), respectively. The predictive values are higher for lipid-level modifying therapies than for other therapies.

Conclusions—

A CIMT trial positioned before an M&M trial may considerably improve the efficiency of the evaluation of new drug therapies on atherosclerosis and cardiovascular disease risk. Hence, the results of a CIMT trial should be seen as a decision tool to support or refute the start of a large-scale M&M trial on drugs targeting atherosclerosis.

Biologically implausible carotid intima-media thickness measurement values: effects on rate of change over time

OBJECTIVE

Carotid intima-media thickness (CIMT) is a marker of atherosclerosis that is commonly used to assess the effect of therapeutic interventions. It is currently unclear to what extent biologically implausible values affect treatment effects. We evaluated the impact of biologically implausible CIMT values on the estimated rate of change in CIMT.

METHODS

Data were used from the METEOR (Measuring Effects on Intima-media Thickness: an Evaluation of Rosuvastatin) trial. METEOR was a randomized, placebo-controlled trial showing that rosuvastatin reduced the 2-year change in CIMT among low-risk individuals with subclinical atherosclerosis. In the main METEOR analysis, the data were analyzed without exclusion of biologically implausible data. In this post-hoc analysis, we constructed twelve definitions to define mildly or extremely biologically implausible values using distance from the interquartile range, median or mean. We evaluated the effect of removing implausible values on the estimated rate of change in CIMT.

RESULTS

The percentage of biologically implausible CIMT values ranged from 0.6% to 9.7%, depending on the definition used. Across all definitions, removal of biologically implausible CIMT values marginally reduced standard errors and did not change the primary outcome (i.e., a nonsignificant change in the rosuvastatin group, significant progression in the placebo group, and a statistically significant difference between treatment groups).

LIMITATION

This study was focussed on the impact of implausible values in the analytical part of a CIMT study. Ultrasound images were not re-examined to determine whether an implausible measurement was due to measurement error or temporal morphological thickening,

CONCLUSION

Removal of biologically implausible CIMT values marginally decreased the variability of the estimated rate of change in CIMT without having a large impact on the estimated rate of change.

Multiple imputation of missing repeated outcome measurements did not add to linear mixed-effects models

OBJECTIVE

To assess the added value of multiple imputation (MI) of missing repeated outcomes measures in longitudinal data sets analyzed with linear mixed-effects (LME) models.

STUDY DESIGN AND SETTING

Data were used from a trial on the effects of Rosuvastatin on rate of change in carotid intima-media thickness (CIMT). The reference treatment effect was derived from a complete data set. Scenarios and proportions of missing values in CIMT measurements were applied and LME analyses were used before and after MI. The added value of MI, in terms of bias and precision, was assessed using the mean-squared error (MSE) of the treatment effects and coverage of the 95% confidence interval.

RESULTS

The reference treatment effect was -0.0177 mm/y. The MSEs for LME analysis without and with MI were similar in scenarios with up to 40% missing values. Coverage was large in all scenarios and was similar for LME with and without MI.

CONCLUSION

Our study empirically shows that MI of missing end point data before LME analyses does not increase precision in the estimated rate of change in the end point. Hence, MI had no added value in this setting and standard LME modeling remains the method of choice.

Long-term physical activity and inflammatory biomarkers in older adults

PURPOSE

The purpose of this study was to determine the effects of a 12-month physical activity (PA) intervention on inflammatory biomarkers in elderly men and women.

METHODS

Four hundred and twenty-four elderly (age = 70-89 yr), nondisabled, community-dwelling men and women at risk for physical disability were enrolled in a multicenter, single-blind, randomized controlled trial. Participants were randomized to participate in either a 12-month moderate-intensity PA intervention or a successful aging health education intervention. Biomarkers of inflammation (interleukin (IL)-6sR, IL-1sRII, soluble tumor necrosis factor receptors 1 and 2 (sTNFRI, sTNFRII), IL-8, IL-15, adiponectin, IL-1ra, IL-2sRα, and TNFα) were measured at baseline, at 6 months, and at 12 months.

RESULTS

A baseline blood sample was successfully collected from 368 participants. After adjustment for gender, clinic site, diabetes status, and baseline outcome measure, IL-8 was the only inflammatory biomarker affected by the PA intervention (P = 0.03). The adjusted mean IL-8 at month 12 was 9.9% (0.87 pg·mL) lower in the PA compared with the successful aging group. Secondary interaction analyses between baseline biomarker status and treatment showed one significant interaction (P = 0.02) such that the PA intervention reduced IL-15 concentrations in participants with a baseline IL-15 above the median value of 1.67 pg·mL. However, these associations were no longer significant after consideration for multiple comparisons.

CONCLUSIONS

Overall, this study does not provide definitive evidence for an effect of regular exercise for altering systemic concentrations of the measured inflammatory biomarkers in older adults.

Completeness of carotid intima media thickness measurements depends on body composition: the RADIANCE 1 and 2 trials

AIM

Ultrasound protocols to measure carotid intima media thickness (CIMT) differ considerably with regard to the inclusion of the number of carotid segments and angles used. Detailed information on the completeness of CIMT information is often lacking in published reports, and at most, overall percentages are presented. We therefore decided to study the completeness of CIMT measurements and its relation with vascular risk factors using data from two CIMT intervention studies: one among familial hypercholesterolemia (FH) patients, the Rating Atherosclerotic Disease change by Imaging With A New CETP Inhibitor (RADIANCE 1), and one among mixed dyslipidemia (MD) patients, the Rating Atherosclerotic Disease change by Imaging With A New CETP Inhibitor (RADIANCE 2).

METHODS

We used baseline ultrasound scans from the RADIANCE 1 (n=872) and RADIANCE 2 (n=752) studies. CIMT images were recorded for 12 artery-wall combinations (near and far walls of the left and right common carotid artery (CCA), bifurcation (BIF) and internal carotid artery (ICA) segments) at 4 set angles, resulting in 48 possible measurements per patient. The presence or absence of CIMT measurements was assessed per artery-wall combination and per angle. The relation between completeness and patient characteristics was evaluated with logistic regression analysis.

RESULTS

In 89% of the FH patients, information on CIMT could be obtained on all twelve carotid segments, and in 7.6%, eleven segments had CIMT information (nearly complete 96.6%). For MD patients this was 74.6% and 17.9%, respectively (nearly complete: 92.5%). Increased body mass index and increased waist circumference were significantly (p=0.01) related to less complete data in FH patients. For MD patients, relations were seen with increased waist circumference (p<0.01). Segment-specific data indicated that in FH patients, completeness was less for the near wall of the left (96%) and right internal carotid artery (94%) as compared to other segments (all >98%). In MD patients, completeness was lower for the near wall of both the right and left carotid arteries: 86.0% and 90.8%, respectively, as compared to other segments (all >97%).

CONCLUSIONS

With the current ultrasound protocols it is possible to obtain a very high level of completeness. Apart from the population studied, body mass index and waist circumference are important in achieving complete CIMT measurements.

Cholesteryl Ester Transfer Protein Inhibitor Torcetrapib and Off-Target Toxicity

Background— Torcetrapib, an inhibitor of cholesteryl ester transfer protein, has been shown to increase the cardiovascular event rate despite conferring a significant high-density lipoprotein cholesterol increase. Using data from the Rating Atherosclerotic Disease Change by Imaging with a New CETP Inhibitor (RADIANCE) trials, which assessed the impact of torcetrapib on carotid intima-media thickness (cIMT), we sought to explore potential mechanisms underlying this adverse outcome.

Methods and Results— Data from the RADIANCE 1 and 2 studies, which examined cIMT in 904 subjects with familial hypercholesterolemia and in 752 subjects with mixed dyslipidemia, were pooled. Subjects were randomized to either atorvastatin or torcetrapib combined with atorvastatin. Mean common cIMT progression was increased in subjects receiving torcetrapib plus atorvastatin compared with subjects receiving atorvastatin alone (0.0076±0.0011 versus 0.0025±0.0011 mm/y; P =0.0014). Subjects treated with torcetrapib plus atorvastatin displayed higher postrandomization systolic blood pressure and plasma sodium and bicarbonate levels in conjunction with lower potassium levels. The decrease in potassium levels was associated with the blood pressure increase. Markedly, the use of renin-angiotensin-aldosterone system inhibitors tended to aggravate the blood pressure increase. Subjects receiving torcetrapib plus atorvastatin with the strongest low-density lipoprotein cholesterol reduction showed the smallest cIMT progression, whereas subjects with the highest systolic blood pressure increase showed the largest cIMT progression. High-density lipoprotein cholesterol increase was not associated with cIMT change.

Conclusions— These analyses support mineralocorticoid-mediated off-target toxicity in patients receiving torcetrapib as a contributing factor to an adverse outcome. The absence of an inverse relationship between high-density lipoprotein cholesterol change and cIMT progression suggests that torcetrapib-induced high-density lipoprotein cholesterol increase does not mediate atheroprotection. Future studies with cholesteryl ester transfer protein inhibitors without off-target toxicity are needed to settle this issue.

Simvastatin with or without ezetimibe in familial hypercholesterolemia

BACKGROUND

Ezetimibe, a cholesterol-absorption inhibitor, reduces levels of low-density lipoprotein (LDL) cholesterol when added to statin treatment. However, the effect of ezetimibe on the progression of atherosclerosis remains unknown.

METHODS

We conducted a double-blind, randomized, 24-month trial comparing the effects of daily therapy with 80 mg of simvastatin either with placebo or with 10 mg of ezetimibe in 720 patients with familial hypercholesterolemia. Patients underwent B-mode ultrasonography to assess the intima-media thickness of the walls of the carotid and femoral arteries. The primary outcome measure was the change in the mean carotid-artery intima-media thickness, which was defined as the average of the means of the far-wall intima-media thickness of the right and left common carotid arteries, carotid bulbs, and internal carotid arteries.

RESULTS

The primary outcome, the mean (+/-SE) change in the carotid-artery intima-media thickness, was 0.0058+/-0.0037 mm in the simvastatin-only group and 0.0111+/-0.0038 mm in the simvastatin-plus-ezetimibe (combined-therapy) group (P=0.29). Secondary outcomes (consisting of other variables regarding the intima-media thickness of the carotid and femoral arteries) did not differ significantly between the two groups. At the end of the study, the mean (+/-SD) LDL cholesterol level was 192.7+/-60.3 mg per deciliter (4.98+/-1.56 mmol per liter) in the simvastatin group and 141.3+/-52.6 mg per deciliter (3.65+/-1.36 mmol per liter) in the combined-therapy group (a between-group difference of 16.5%, P<0.01). The differences between the two groups in reductions in levels of triglycerides and C-reactive protein were 6.6% and 25.7%, respectively, with greater reductions in the combined-therapy group (P<0.01 for both comparisons). Side-effect and safety profiles were similar in the two groups.

CONCLUSIONS

In patients with familial hypercholesterolemia, combined therapy with ezetimibe and simvastatin did not result in a significant difference in changes in intima-media thickness, as compared with simvastatin alone, despite decreases in levels of LDL cholesterol and C-reactive protein. (ClinicalTrials.gov number, NCT00552097 [ClinicalTrials.gov].).

Torcetrapib and carotid intima-media thickness in mixed dyslipidaemia (RADIANCE 2 study): a randomised, double-blind trial

BACKGROUND

Patients with mixed dyslipidaemia have raised triglycerides, low high-density lipoprotein (HDL) cholesterol, and high low-density lipoprotein (LDL) cholesterol. Augmentation of HDL cholesterol by inhibition of the cholesteryl ester transfer protein (CETP) could benefit these patients. We aimed to investigate the effect of the CETP inhibitor, torcetrapib, on carotid atherosclerosis progression in patients with mixed dyslipidaemia.

METHODS

We did a randomised double-blind trial at 64 centres in North America and Europe. 752 eligible participants completed an atorvastatin-only run-in period for dose titration, after which they all continued to receive atorvastatin at the titrated dose. 377 of these patients were randomly assigned to receive 60 mg of torcetrapib per day and 375 to placebo. We made carotid ultrasound images at baseline and at 6-month intervals for 24 months. The primary endpoint was the yearly rate of change in the maximum intima-media thickness of 12 carotid segments. Analysis was restricted to 683 patients who had at least one dose of treatment and had at least one follow-up carotid intima-media measurement; they were analysed as randomised. Mean follow-up for these patients was 22 (SD 4.8) months. This trial is registered with ClinicalTrials.gov, number NCT00134238.

FINDINGS

The change in maximum carotid intima-media thickness was 0.025 (SD 0.005) mm per year in patients given torcetrapib with atorvastatin and 0.030 (0.005) mm per year in those given atorvastatin alone (difference -0.005 mm per year, 95% CI -0.018 to 0.008, p=0.46). Patients in the combined-treatment group had a 63.4% relative increase in HDL cholesterol (p<0.0001) and an 17.7% relative decrease in LDL cholesterol (p<0.0001), compared with controls. Systolic blood pressure increased by 6.6 mm Hg in the combined-treatment group and 1.5 mm Hg in the atorvastatin-only group (difference 5.4 mm Hg, 95% CI 4.3-6.4, p<0.0001).

INTERPRETATION

Although torcetrapib substantially raised HDL cholesterol and lowered LDL cholesterol, it also increased systolic blood pressure, and did not affect the yearly rate of change in the maximum intima-media thickness of 12 carotid segments. Torcetrapib showed no clinical benefit in this or other studies, and will not be developed further.

Effect of torcetrapib on carotid atherosclerosis in familial hypercholesterolemia

BACKGROUND

Torcetrapib, an inhibitor of cholesteryl ester transfer protein, may reduce atherosclerotic vascular disease by increasing levels of high-density lipoprotein (HDL) cholesterol.

METHODS

A total of 850 patients with heterozygous familial hypercholesterolemia underwent B-mode ultrasonography at baseline and at follow-up to measure changes in carotid intima-media thickness. The patients completed an atorvastatin run-in period and were subsequently randomly assigned to receive either atorvastatin monotherapy or atorvastatin combined with 60 mg of torcetrapib for 2 years.

RESULTS

After 24 months, in the atorvastatin-only group, the mean (+/-SD) HDL cholesterol level was 52.4+/-13.5 mg per deciliter and the mean low-density lipoprotein (LDL) cholesterol level was 143.2+/-42.2 mg per deciliter, as compared with 81.5+/-22.6 mg per deciliter and 115.1+/-48.5 mg per deciliter, respectively, in the torcetrapib-atorvastatin group. During the study, average systolic blood pressure increased by 2.8 mm Hg in the torcetrapib-atorvastatin group, as compared with the atorvastatin-only group. The increase in maximum carotid intima-media thickness, the primary measure of efficacy, was 0.0053+/-0.0028 mm per year in the atorvastatin-only group and 0.0047+/-0.0028 mm per year in the torcetrapib-atorvastatin group (P=0.87). The secondary efficacy measure, annualized change in mean carotid intima-media thickness for the common carotid artery, indicated a decrease of 0.0014 mm per year in the atorvastatin-only group, as compared with an increase of 0.0038 mm per year in the torcetrapib-atorvastatin group (P=0.005).

CONCLUSIONS

In patients with familial hypercholesterolemia, the use of torcetrapib with atorvastatin, as compared with atorvastatin alone, did not result in further reduction of progression of atherosclerosis, as assessed by a combined measure of carotid arterial-wall thickness, and was associated with progression of disease in the common carotid segment. These effects occurred despite a large increase in HDL cholesterol levels and a substantial decrease in levels of LDL cholesterol and triglycerides. (ClinicalTrials.gov number, NCT00136981 [ClinicalTrials.gov].).

Diabetes and progression of carotid atherosclerosis: the insulin resistance atherosclerosis study

OBJECTIVE

We sought to determine the rate of progression of carotid atherosclerosis in persons with normal glucose tolerance, impaired glucose tolerance, and undiagnosed and diagnosed type 2 diabetes.

METHODS AND RESULTS

The Insulin Resistance Atherosclerosis Study (IRAS) is an observational cohort study in which 1192 men and women were examined at a 5-year interval. Participants of 3 ethnic groups (non-Hispanic white, African American, and Hispanic) were selected from the general population to represent a range of glucose tolerance. Baseline and follow-up ultrasound studies were obtained to estimate progression of common carotid artery (CCA) and internal carotid artery (ICA) intimal-medial thickness (IMT). Baseline glucose tolerance status was defined by an oral glucose tolerance test and World Health Organization criteria. In persons with normal glucose tolerance, progression of CCA IMT was 3.8 microm/y, and ICA IMT, 17.7 microm/y. In both CCA and ICA, progression of IMT, unadjusted for cardiovascular disease (CVD) risk factors, was approximately twice the rate in persons with diabetes than in those with normal or impaired glucose tolerance. Adjustment for CVD risk factors attenuated these differences somewhat in both sites of the carotid artery. Persons with undiagnosed diabetes had a greater ICA IMT progression rate than did persons with diagnosed diabetes (33.9 microm/y vs 26.6 microm/y, P=NS). Progression rates did not differ between persons with normal and impaired glucose tolerance.

CONCLUSIONS

Progression of carotid atherosclerosis is accelerated in persons with diabetes. Progression of ICA IMT is most pronounced in persons with undiagnosed diabetes. Early identification of diabetes and CVD risk factor control might reduce its atherosclerotic complications.

Associations of extracranial carotid atherosclerosis progression with coronary status and risk factors in patients with and without coronary artery disease

BACKGROUND

Intimal medial thickness of the extracranial carotid arteries (IMT) is related to coronary artery disease (CAD) and CAD risk factors. Few studies have explored the association of risk factors with progression of IMT, and none have evaluated their associations with IMT progression specifically in patients with and without CAD.

METHODS AND RESULTS

We used coronary angiography to identify 280 patients equally divided between men and women and those with either > or =50% coronary artery stenosis or no CAD. Risk factors were measured at baseline and IMT was measured at baseline and yearly for 3 years in 241 of these individuals. Baseline risk factors and CAD status were related to IMT progression. IMT of patients with CAD progressed 3 times faster than that of patients with no CAD (mean+/-SEM, 33.7+/-7.4 versus 8.9+/-7.1 microm/year; P=0.02), and CAD status and high-density lipoprotein (HDL) cholesterol were independently associated with IMT progression. Male sex, increased waist to hip ratio, cigarette smoking, increased triglycerides, and decreased HDL cholesterol were associated with increased progression in CAD patients.

CONCLUSIONS

Patients with CAD have more rapid progression of IMT than CAD-free controls, and risk factors are related to progression in them.