Metabolic cardiovascular syndrome and risk of dementia in Japanese-American elderly men. The Honolulu-Asia aging study

Prevention and treatment of the metabolic syndrome

The prevalence of the metabolic syndrome is increasing owing to lifestyle changes leading to obesity. This syndrome is a complex association of several interrelated abnormalities that increase the risk for cardiovascular disease and progression to diabetes mellitus (DM). Insulin resistance is the key factor for the clustering of risk factors characterizing the metabolic syndrome. The National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III defined the criteria for the diagnosis of the metabolic syndrome and established the basic principles for its management. According to these guidelines, treatment involves the improvement of the underlying insulin resistance through lifestyle modification (eg, weight reduction and increased physical activity) and possibly by drugs. The coexistent risk factors (mainly dyslipidemia and hypertension) should also be addressed. Since the main goal of lipid-lowering treatment is to achieve the NCEP low-density lipoprotein cholesterol (LDL-C) target, statins are a good option. However, fibrates (as monotherapy or in combination with statins) are useful for the treatment of the metabolic syndrome that is commonly associated with hypertriglyceridemia and decreased high-density lipoprotein cholesterol (HDL-C) levels. The blood pressure target is < 140/90 mm Hg. The effect on carbohydrate homeostasis should possibly be taken into account in selecting an antihypertensive drug. Patients with the metabolic syndrome commonly have other less well-defined metabolic abnormalities (eg, hyperuricemia and raised C-reactive protein levels) that may also be associated with an increased cardiovascular risk. It seems appropriate to manage these abnormalities. Drugs that beneficially affect carbohydrate metabolism and delay or even prevent the onset of DM (eg, thiazolidinediones or acarbose) could be useful in patients with the metabolic syndrome. Furthermore, among the more speculative benefits of treatment are improved liver function in nonalcoholic fatty liver disease and a reduction in the risk of acute gout.

The nature and effects of cortical microvascular pathology in aging and Alzheimer's disease

Age-related and amyloid-induced pathology of the cerebral microvasculature have been implicated as potential contributing factors to the pathogenesis of Alzheimer's disease (AD). The microvasculature plays a crucial role in maintaining brain homeostasis and deterioration of its integrity may have deleterious effects on brain function in AD, possibly leading to neurofibrillary degeneration, plaque formation, and cell loss. Brain vessels possess peculiar anatomical and physiological properties owing to their role in the exchange processes of various substances between blood and brain, which are highly regulated for the maintenance of ionic homeostasis of the neuronal environment. Here we review neuropathological aspects of cortical microvessels in aging and AD in relationship to known cardiovascular risk factors and their possible impact on the cognitive decline seen in late-onset dementia.

The effects of exercise training on elderly persons with cognitive impairment and dementia: a meta-analysis

OBJECTIVE

To determine by meta-analysis whether physical exercises are beneficial for people with dementia and related cognitive impairments.

DATA SOURCES

Published articles and nonpublished manuscripts from 1970 to 2003 were identified by using electronic and manual searches. Key search words included exercise, rehabilitation, activities of daily living, dementia, Alzheimer's disease, aged, and geriatrics.

STUDY SELECTION

Reviewed studies were limited to randomized trials evaluating exercise in persons 65 years of age or older with cognitive impairment. Studies included quantitative results (means, standard deviations, t tests, F tests) for physical fitness, physical functioning, cognition, or behavior outcomes.

DATA EXTRACTION

One reviewer extracted data on study characteristics and findings. Selected articles were evaluated for methodologic quality by 2 raters.

DATA SYNTHESIS

A total of 2020 subjects participated in the 30 trials that met the inclusion criteria. Summary effects were computed using a fixed effects (Hedge's g(i)) model. Significant summary effect sizes (ES) were found for strength (ES=.75; 95% confidence interval [CI], .58-.92), physical fitness (ES=.69; 95% CI, .58-.80), functional performance (ES=.59; 95% CI, .43-.76), cognitive performance (ES=.57; 95% CI, 0.43-1.17), and behavior (ES=.54; 95% CI, .36-.72). The overall mean ES between exercise and nonexercise groups for all outcomes was .62 (95% CI, .55-.70).

CONCLUSIONS

Exercise training increases fitness, physical function, cognitive function, and positive behavior in people with dementia and related cognitive impairments.

Cardiovascular risk factors and Alzheimer's disease

Alzheimer's disease is a devastating condition that is increasing in prevalence. No known prevention or cure exists for Alzheimer's disease. Cardiovascular risk factors are prevalent and increase in the elderly, and there have been conflicting reports of associations between modifiable cardiovascular risk factors and Alzheimer's disease. The mechanisms for these associations are uncertain, but they are likely to be the result of a combination of direct and cerebrovascular disease-related mechanisms. From this standpoint, diabetes and hyperinsulinemia seem to have the strongest evidence from laboratory, clinical, and epidemiologic studies. Studies have also indicated that hypertension, hyperlipidemia, hyperhomocysteinemia, and smoking are potentially important risk factors for Alzheimer's disease.

Cardiovascular risk factors and cognitive function in adults 30-59 years of age (NHANES III)

In the Third National Health and Nutrition Examination Survey (NHANES III), three measures of cognitive function [Simple Reaction Time Test (SRTT), Symbol Digit Substitution Test (SDST), and Serial Digit Learning Test (SDLT)] were administered to a half-sample of 3,385 adult men and nonpregnant women 30-59 years of age with no history of stroke. We used multiple linear regression analysis to determine whether there was an independent association between performance on each cognitive function measure and defined hypertension (HTN) alone, type 2 diabetes mellitus (DM) alone, and coexistent HTN and DM after adjustment for demographic and socioeconomic variables and selected health behaviors. After adjustment for the sociodemographic variables, the combination of HTN + DM, but not HTN alone or DM alone, was significantly associated with worse performance on the SRTT (p = 0.031) and the SDST (p = 0.011). A similar pattern was observed for SDLT performance, but the relationship did not reach statistical significance (p = 0.101). We conclude that HTN in combination with DM is associated with detectable cognitive decrements in persons under age 60.

Convergence of atherosclerosis and Alzheimer's disease: inflammation, cholesterol, and misfolded proteins

Late-onset sporadic Alzheimer's disease is a heterogeneous disorder. In elderly patients, increasing evidence suggests a link between this neurodegenerative disease, and vascular risk factors and atherosclerosis. The nature of this link remains speculative. Some investigators have suggested that the disease arises as a secondary event related to atherosclerosis of extracranial or intracranial vessels. A toxic effect of vascular factors on the microvasculature of susceptible brain regions has also been argued. An alternative explanation is that atherosclerosis and Alzheimer's disease are independent but convergent disease processes. This hypothesis is lent support by observations of shared epidemiology, pathophysiological elements, and response to treatment in both disorders. It provides a potential framework for an improved understanding of the pathogenesis of Alzheimer's disease, especially in elderly patients with vascular risk factors, and offers some promise toward the search for preventive and therapeutic treatments.

Vers une prévention de la démence ?

Many studies have shown that high blood pressure and, to a lesser extent, other vascular risk factors could be the target of interventions aiming to reduce the incidence of dementia. Two large controlled trials have demonstrated that blood pressure lowering drugs have a significant effect on the risk of dementia including Alzheimer's disease. On another hand, large epidemiological studies have shown associations between different vascular factors and dementia. Overall, these data suggest that interventions aiming to reduce the level of vascular risk factors might prevent dementia. The expected benefit of these interventions could be estimated from data provided by epidemiological studies, but large population-based controlled studies are needed to demonstrate the efficacy of preventive interventions.

A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning

We have investigated a potential mechanism by which a diet, similar in composition to the typical diet of most industrialized western societies rich in saturated fat and refined sugar (HFS), can influence brain structure and function via regulation of neurotrophins. We show that animals that learn a spatial memory task faster have more brain-derived neurotrophic factor (BDNF) mRNA and protein in the hippocampus. Two months on the HFS diet were sufficient to reduce hippocampal level of BDNF and spatial learning performance. Consequent to the action of BDNF on synaptic function, downstream effectors for the action of BDNF on synaptic plasticity were reduced proportionally to BDNF levels, in the hippocampus of rats maintained on the HFS diet between 2 and 24 months. In particular, animals maintained on the HFS diet showed a decrease in levels of: (i) synapsin I mRNA and protein (total and phosphorylated), important for neurotransmitter release; (ii) cyclic AMP-response element-binding protein (CREB) mRNA and protein (total and phosphorylated); CREB is required for various forms of memory and is under regulatory control of BDNF; (iii) growth-associated protein 43 mRNA, important for neurite outgrowth, neurotransmitter release, and learning and memory. Diet-related changes were specific for the hippocampus consequent to its role in memory formation, and did not involve neurotrophin-3, another member of the neurotrophin family. Our results indicate that a popularly consumed diet can influence crucial aspects of neuronal and behavioral plasticity associated with the function of BDNF.

The impact of the use of statins on the prevalence of dementia and the progression of cognitive impairment

BACKGROUND

Previous evidence suggests that treatment with 3-hydroxy-3-methylglutaryl-coenzyme-A reductase inhibitors (statins) has a positive impact on dementia. We decided to investigate the association between the use of statins and the prevalence of dementia and statins' impact on the progression of cognitive impairment.

METHODS

This is a case-control and a retrospective cohort study of a community-based ambulatory primary care geriatric practice. We included a convenience sample of all patients (N = 655, mean age 78.7 +/- 0.3 years, 85% Caucasian, 74% women) with hypercholesterolemia or dementia, or using statins. We compared those using statins with those who do not with respect to the clinical diagnosis of dementia and its subtypes and the progression of cognitive impairment.

RESULTS

At the initial visit, 35% had dementia, and 17% were using statins. After covariate adjustments, patients on statins were less likely to have dementia (odds ratio [OR] for dementia based on composite definition = 0.23; 95% confidence interval [CI] [0.1-0.56], p =.001, OR Alzheimer's disease = 0.37; 95% CI [0.19-0.74], p =.005, OR vascular dementia = 0.25; 95% CI [0.08-0.85], p =.027). At follow-up, patients on statins showed an improvement on their Mini-Mental Status Examination score by 0.7 +/- 0.4 compared to a decline by 0.5 +/- 0.3 in controls, p =.025 (OR for no change or improvement on statins = 2.81; 95% CI [1.02-8.43], p =.045) and scored higher on the Clock Drawing Test (difference of 1.5 +/- 0.1, p =.036).

CONCLUSIONS

The use of statins is associated with a lower prevalence of dementia and has a positive impact on the progression of cognitive impairment.

Effect of the treatment of Type II diabetes mellitus on the development of cognitive impairment and dementia

BACKGROUND

There is increasing interest in preventing cognitive impairment and dementia in later life. Epidemiological evidence shows a relationship between cognitive impairment and Type II diabetes. This association is stronger in patients who have been diagnosed for longer periods of time and in those who are on insulin therapy. There is little information on the short- and long-term influence of type of treatment and level of metabolic control on cognitive function of people with diabetes.

OBJECTIVES

To assess the effects of different types and intensities of treatments for Type II diabetes on cognitive function.

SEARCH STRATEGY

The Cochrane Control Trials Register, MEDLINE, EMBASE, PsycINFO, SIGLE LILACS and CINAHL as well as a number of ongoing trials databases were searched on 11 June 2002 using appropriate strategies.

SELECTION CRITERIA

Randomized controlled trials in which different treatments for Type II diabetes have been compared and in which measures of cognitive function were made at entry and after the treatment.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality. Five trials were identified for possible inclusion but none of them could be included. In one, cognitive function was assessed before and after intensive or conventional diabetic treatment, but the comparison was not double-blind. The three other studies explored the effect of different treatments on QOL but did not include appropriate evaluation of cognitive function. The fifth did not report baseline data on cognitive function in the trial groups.

MAIN RESULTS

No studies were found to be appropriate for inclusion in meta-analysis.

REVIEWER'S CONCLUSIONS

There is no convincing evidence relating type or intensity of diabetic treatment to the prevention or management of cognitive impairment in Type II diabetes. Future research on treatments for diabetes should include standardized assessments of cognitive function as outcome measures.