Cholesterol, stroke risk, and stroke prevention

Global, regional and national burden of ischemic stroke attributed to high low-density lipoprotein cholesterol, 1990-2019：A decomposition analysis and age-period-cohort analysis

High levels of low-density lipoprotein cholesterol (LDL-C) have been associated with an augmented mortality of ischemic stroke. The yearly deaths and mortality data of IS-hLDL-C were derived from the global burden of disease 2019 dataset. The joinpoint, age-period-cohort and decomposition analysis were utilized to evaluate the long-term patterns in the disease burden of IS-hLDL-C, and the effects of population growth and aging. Globally, in 2019, 0.61 million ischemic stroke-related deaths were attributable to high LDL-C, with the highest death burden in the high-middle socio-demographic index (SDI) region. From 1990 to 2019, the age-standardized death rate (ASDR) for IS-hLDL-C exhibited a downward trend, with an average annual percentage change of -1.69 [95% confidence interval: -1.90, -1.48)]. The fastest decreasing trends in ASDR were experienced in the high SDI region. In 119 (58.33%) countries, aging increased the disease burden of hLDL-IS, and population growth increased the disease burden of IS-hLDL-C in 163 (79.90%) countries. The trend in disease burden of IS-hLDL-C exhibited variation across countries and regions, particularly in territories with high to middle high SDI. Aging in upper to middle-income countries and population growth in low to middle-income countries further offset endeavors to reduce the burden of ischemic stroke deaths.

Stroke Risk Factors of Stroke Patients in China: A Nationwide Community-Based Cross-Sectional Study

Background: Stroke is the leading cause of death in China, and its burdens are rapidly increasing. The prevalence and control of stroke risk factors among stroke patients in China are unknown. Objective: We investigated the stroke risk factors of stroke patients in China. Design: We examined stroke risk factors in 6580 stroke patients aged 18 years or older in the China National Chronic Diseases and Nutrition Surveillance of Adults (2015–2017). With regard to the basic characteristics of the study participants, categorical variables were described as frequency (percent). The chi-square test was used to analyze the difference between men and women. The multivariate logistic regression model was used in the multivariate analysis. Results: Among the 6580 stroke patients, hypertension was the most common stroke risk factor identified in most cases (78.51%), followed by overweight or obesity (61.58%), dyslipidemia (54.38%), smoking (24.04%), diabetes (21.75%), family history of stroke (17.43%), lack of exercise (16.35%), and atrial fibrillation (4.47%). Drinking stroke patients had a lower rate of hypertension, diabetes, and dyslipidemia. Patients with hyperuricemia had a higher rate of hypertension and dyslipidemia than no-hyperuricemia patients. The hypertension awareness, treatment, and control rates among hypertension stroke patients were 73.62%, 70.19%, and 17.79%, respectively. The diabetes awareness, treatment, and control rates among diabetes patients were 69.74%, 65.83%, and 34.59%, respectively. The dyslipidemia awareness, treatment, and control rates among dyslipidemia patients were 42.37%, 29.4%, and 20.07%, respectively. Among treated hypertension patients, the rates of taking medicine as medically advised, controlled diet, increased exercise, and blood pressure monitoring were 91.31%, 58.88%, 45.78%, and 73.99%, respectively. Among treated diabetes patients, the rates of oral antidiabetic medications, insulin injection, diet control, and blood glucose monitoring were 78.24%, 34.71%, 85.77%, and 78.24%, respectively. Among treated dyslipidemic patients, the rate of taking medicine as medical advice, controlled diet, increased exercise, and regular blood lipid monitoring was 80.61%, 77.57%, 56.46%, and 40.3%, respectively. Conclusions: The most common risk factors for community stroke patients in China are hypertension, dyslipidemia, and overweight or obesity. The stroke community patients’ suboptimal awareness and treatment of hypertension, and suboptimal awareness, treatment, and control of diabetes, and dyslipidemia are significant problems in China.

Ischemic and Non-ischemic Stroke in Young Adults - A Look at Risk Factors and Outcome in a Developing Country

Objective Stroke among young adults is the leading cause of disability worldwide. Efforts are being taken to control stroke in the general population, but in parallel, there is an increasing trend of stroke among the young population. These patients are often affected by physical disability, cognitive impairment, and loss of productivity, all of which have personal, social, and economic implications. The main aim of this study was to determine the risk factors associated with stroke among young patients admitted to a tertiary care rehabilitation center and determine the effect of rehabilitation on the outcome of their daily life activities. Materials and Methods A retrospective hospital-based cohort study was conducted between January 2015 to December 2019. Prevalence of stroke-related risk factors like hypertension, hyperlipidemia, diabetes, and cardiac disease was assessed. Results Out of 710 young stroke adults, 71.97% were described as ischemic, and 28.03% reported as non-ischemic. Mean age (SD) was found to be 44.54 ± 9.3. Univariate analysis demonstrated that hyperlipidemia, cardiac disease, and diabetes indicated a significantly higher risk for ischemic stroke with an OR (95% CI) at 2.5 (1.7-3.7), 2.11 (1.2-3.6), and 1.66 (1.2-2.3) respectively. A significant improvement was observed in their Functional Independence Measure (FIM0 score after their rehabilitation irrespective of age and gender. Conclusion Association of risk factors associated with stroke should be subjected to close follow-up and management, thus reducing the risk of developing long-lasting disabilities at a young age. The identification of risk factors for young stroke incidence is a step towards improving health in the young adult population.

Association Between Vascular Overload Index and New-Onset Ischemic Stroke in Elderly Population with Hypertension

Background

Vascular overload index (VOI) is a marker of arterial stiffness and arteriolar resistance, which predicts the increasing risks of cardiovascular and cerebrovascular disease. This study aimed to evaluate the association between VOI and new-onset ischemic stroke in an elderly population with hypertension.

Methods

This retrospective cohort study included 3315 hypertensive participants aged 60 years or more. Ischemic stroke was diagnosed according to cranial computed tomography, magnetic resonance imaging of the brain or cerebrovascular angiography. The calculation of VOI was based on systolic and diastolic blood pressure. VOI was divided by quartiles (<7.88 mmHg, 7.88–16.10 mmHg, 16.10–27.14 mmHg, ≥27.14 mmHg) and evaluated the association with new-onset ischemic stroke by multivariable Cox regression models.

Results

A total of 3315 participants (55.5% female) aged 71.4±7.20 years were included in the analysis. The median follow-up period was 5.5 years, and 206 participants reached the endpoint, new-onset ischemic stroke. With per standard deviation increment in VOI, the risks of new-onset ischemic stroke increased in non-adjusted model (Hazard ratio [HR], 1.11; 95% confidence interval [CI]: 1.03–1.22; p = 0.001), adjusted model (HR, 1.11; 95% CI: 1.04–1.22; p = 0.003) and fully-adjusted model (HR, 1.15; 95% CI: 1.08–1.26; p<0.001), respectively. In multivariate fully adjusted model, the risks of ischemic stroke increased in higher quartiles in comparison to the first quartiles (p for trend <0.001).

Conclusion

In an elderly hypertensive population, VOI is significantly associated with the incidence of new-onset ischemic stroke. Elevated VOI is the cardiovascular risk factor and increases the probability of new-onset ischemic stroke.

Characteristics and Risk Factors Associated with Stroke Subtypes among Adult Patients Admitted to the Stroke Unit of Jimma University Medical Center: A Retrospective Cross-sectional Study

BACKGROUND

Almost 80% of deaths due to non-communicable diseases occur in lowand middle-income countries. Stroke is a great public health problem in Ethiopia. Stroke mortality was estimated to be 14.7% in Ethiopia. Despite this, researches done in Ethiopia on factors associated with stroke sub-types were inadequate.

OBJECTIVE

To assess the characteristics and risk factors associated with stroke subtypes among patients admitted to Jimma University Medical Center.

MATERIALS AND METHODS

A retrospective cross-sectional study was conducted from May 2017 to May 2018 in the stroke unit of the Jimma University Medical Center. A total of 106 medical charts of patients diagnosed with stroke were reviewed. A checklist comprising relevant variables was used to collect data. SPSS version 21 was employed for data entry and analysis. Pearson chi-square test was used to check the association of different parameters with stroke subtypes. A P-value <0.05 was used as a cutoff point to declare statistical significance. Data were presented using text, tables, and figures.

RESULTS

From a total of 106 patients, 67 (63.2%) were men. The mean ± SD of age was 52.67±12.46 Year's, and the difference was not significant among stroke subtypes. Among all patients, 59 (55.6%) had ischemic strokes and 47 (44.4%) had hemorrhagic strokes. The most prevalent risk factors significantly associated with stroke subtypes were being male 67 (63.2%) followed by dyslipidemia 43 (40.5%) and cigarette smoking 38 (35.8%).

CONCLUSION

The ischemic stroke was reported to be higher than hemorrhagic in this study. The overall mean (±SD) age of the patient was 52.67±(12.46) years. The mean age of hemorrhagic stroke patients was 55.98 (±13.77) years; while in ischemic stroke was 50.03 (±10.70) years. Being male, a history of cigarette smoking, and dyslipidemia were significantly associated with stroke subtypes.

Alteration of Microbiome Profile by D-Allulose in Amelioration of High-Fat-Diet-Induced Obesity in Mice

Recently, there has been a global shift in diet towards an increased intake of energy-dense foods that are high in sugars. D-allulose has received attention as a sugar substitute and has been reported as one of the anti-obesity food components; however, its correlation with the intestinal microbial community is not yet completely understood. Thirty-six C57BL/6J mice were divided in to four dietary groups and fed a normal diet (ND), a high-fat diet (HFD, 20% fat, 1% cholesterol, w/w), and a HFD with 5% erythritol (ERY) and D-allulose (ALL) supplement for 16 weeks. A pair-feeding approach was used so that all groups receiving the high-fat diet would have the same calorie intake. As a result, body weight and body fat mass in the ALL group were significantly decreased toward the level of the normal group with a simultaneous decrease in plasma leptin and resistin. Fecal short-chain fatty acid (SCFA) production analysis revealed that ALL induced elevated total SCFA production compared to the other groups. Also, ALL supplement induced the change in the microbial community that could be responsible for improving the obesity based on 16S rRNA gene sequence analysis, and ALL significantly increased the energy expenditure in Day(6a.m to 6pm). Taken together, our findings suggest that 5% dietary ALL led to an improvement in HFD-induced obesity by altering the microbiome community.

Prevalence of Stroke Risk Factors and Their Distribution Based on Stroke Subtypes in Gorgan: A Retrospective Hospital-Based Study-2015-2016

Background

Stroke is a leading cause of death and disability worldwide. According to the Iranian Ministry of Medical Health and Education, out of 100,000 stroke incidents in the country, 25,000 lead to death. Thus, identifying risk factors of stroke can help healthcare providers to establish prevention strategies. This study was conducted to investigate the prevalence of stroke risk factors and their distribution based on stroke subtypes in Sayad Shirazi Hospital, Gorgan, Northeastern Iran.

Material and Methods

A retrospective hospital-based study was conducted at Sayad Shirazi Hospital in Gorgan, the only referral university hospital for stroke patients in Gorgan city. All medical records with a diagnosis of stroke were identified based on the International Classification of Diseases, Revision 10, from August 23, 2015, to August 22, 2016. A valid and reliable data gathering form was used to capture data about demographics, diagnostics, lifestyle, risk factors, and medical history.

Results

Out of 375 cases, two-thirds were marked with ischemic stroke with mean ages (standard deviation) of 66.4 (14.2) for men and 64.6 (14.2) for women. The relationship between stroke subtypes and age groups (P=0.008) and hospital outcome (P=0.0001) was significant. Multiple regression analysis showed that hypertension (Exp. (B) =1.755, P=0.037), diabetes mellitus (Exp. (B) =0.532, P=0.021), and dyslipidemia (Exp. (B) =2.325, P=0.004) significantly increased the risk of ischemic stroke.

Conclusion

Overall, hypertension, diabetes mellitus, and dyslipidemia were the major risk factors of stroke in Gorgan. Establishment of stroke registry (population- or hospital-based) for the province is recommended.

Relationship of Periodontal Disease and Edentulism to Stroke/TIA

Periodontitis has been shown to increase the systemic inflammatory response, which has been implicated in atherosclerosis and cerebrovascular events. We hypothesized an association between periodontitis or edentulism and Stroke/TIA in the ARIC Study. Data on 9415 dentate and 1491 edentulous adults included demographics, cardiovascular outcomes, lifestyle, laboratory measures, and, for 6436 of the dentate, a dental examination. The dependent variable was Stroke/TIA, and the exposure was extent (%) of attachment level 3+ millimeters (AL). Quartiles of AL and edentulism were compared for Stroke/TIA using odds ratios (OR) and 95% confidence intervals (CI), and confounders were controlled by logistic regression. Stroke/TIA was prevalent in 13.5% of periodontal examinees, 15.6% of dentate non-examinees, and 22.5% of edentulous persons. The highest quartile of AL (OR 1.3, CI 1.02-1.7) and edentulism (OR 1.4, CI 1.5-2.0) were associated with Stroke/TIA.

The Effects of Chunghyul-Dan (A Korean Medicine Herbal Complex) on Cardiovascular and Cerebrovascular Diseases: A Narrative Review

Chunghyul-dan (CHD) is a herbal complex containing 80% ethanol extract and is composed of Scutellariae Radix, Coptidis Rhizoma, Phellodendri Cortex, Gardeniae Fructus, and Rhei Rhizoma. We have published several experimental and clinical research articles on CHD. It has shown antilipidemic, antihypertensive, antiatherosclerotic, and inhibitory effects on ischemic stroke recurrence with clinical safety in the previous studies. The antilipidemic effect of CHD results from 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and pancreatic lipase-inhibitory activity. The antihypertensive effect likely results from the inhibitory effect on endogenous catecholamine(s) release and harmonization of all components showing the antihypertensive effects. Furthermore, anti-inflammatory and antioxidant effects on endothelial cells are implicated to dictate the antiatherosclerotic effects of CHD. It also showed neuroprotective effects on cerebrovascular and parkinsonian models. These effects of CHD could be helpful for the prevention of the recurrence of ischemic stroke. Therefore, we suggest that CHD could be a promising medication for treating and preventing cerebrovascular and cardiovascular diseases. However, to validate and better understand these findings, well-designed clinical studies are required.

Genetic susceptibility to cerebrovascular disease

PURPOSE OF REVIEW

Cerebrovascular disease (CeVD) remains a major cause of death and a leading cause of disability worldwide. CeVD is a complex and multifactorial disease caused by the interaction of vascular risk factors, environment, and genetic factors. In the present article, we discussed genetic susceptibility to CeVD, with particular emphasis on genetic studies of the associations between lipid traits and CeVD.

RECENT FINDINGS

Several animal and clinical studies clearly defined genetic predisposition to atherosclerosis and CeVD, and particularly to ischemic stroke. Recent evidence has shown that traditional vascular risk factors explain only a small proportion of variance in atherosclerosis, suggesting that additional nontraditional factors and novel genetic determinants impact CeVD. With the help of genome-wide technology, novel genetic variants have been implicated in CeVD and lipid metabolism such as those in protein convertase subtilisin/kexin type 9 (PCSK9) gene in stroke and familial hypercholesterolemia. These studies are important as they contribute to our understanding of the genetic mechanisms underlying CeVD and to developing more effective CeVD prevention strategies.

SUMMARY

CeVD is a complex and multifactorial disease and genetics likely plays an important role in its pathogenesis. The gene-gene and gene-environment interactions of genes involved in biology of vascular disease, including the lipid metabolism are important factors for individual susceptibility to CeVD. Accounting for individual variation in genes, environment and lifestyle will bring us closer to precision medicine, which is an emerging and recently introduced new approach for disease treatment and prevention in clinical practice.

Genetics of ischemic stroke, stroke-related risk factors, stroke precursors and treatments

Stroke remains a leading cause of death worldwide and the first cause of disability in the western world. Ischemic stroke (IS) accounts for almost 80% of the total cases of strokes and is a complex and multifactorial disease caused by the combination of vascular risk factors, environment and genetic factors. Investigations of the genetics of atherosclerosis and IS has greatly enhanced our knowledge of this complex multifactorial disease. In this article we sought to review common single-gene disorders relevant to IS, summarize candidate gene and genome-wide studies aimed at discovering genetic stroke risk factors and subclinical phenotypes, and to briefly discuss pharmacogenetics related to stroke treatments. Genetics of IS is, in fact, one of the most promising research frontiers and genetic testing may be helpful for novel drug discoveries as well as for appropriate drug and dose selection for treatment of patients with cerebrovascular disease.

Epidemiology and risk factors of cerebral ischemia and ischemic heart diseases: similarities and differences

Cerebral ischemia and ischemic heart diseases, common entities nowadays, are the main manifestation of circulatory diseases. Cardiovascular diseases, followed by stroke, represent the leading cause of mortality worldwide. Both entities share risk factors, pathophisiology and etiologic aspects by means of a main common mechanism, atherosclerosis. However, each entity has its own particularities. Ischemic stroke shows a variety of pathogenic mechanisms not present in ischemic heart disease. An ischemic stroke increases the risk of suffering a coronary heart disease, and viceversa. The aim of this chapter is to review data on epidemiology, pathophisiology and risk factors for both entities, considering the differences and similarities that could be found in between them. We discuss traditional risk factors, obtained from epidemiological data, and also some novel ones, such as hyperhomocisteinemia or sleep apnea. We separate risk factors, as clasically, in two groups: nonmodifiables, which includes age, sex, or ethnicity, and modifiables, including hypertension, dyslipidemia or diabetis, in order to discuss the role of each factor in both ischemic events, ischemic stroke and coronary heart disease.

Stroke pharmacogenomics

Circulatory disease accounts for fifteen million deaths each year, of which stroke accounts for four and a half million- with an estimated nine million stroke survivors annually. The overall incidence rate of stroke is 2 to 2.5 per thousand adults with an approximate prevalence of 5 per thousand and an estimated 5-year risk of stroke recurrence of 15 to 40 percent. Conventional risk factors for stroke include: increasing age, hypertension, diabetes mellitus, smoking, increased body mass index, ischemic heart disease, heart failure, atrial fibrillation and lack of physical activity. Age is the strongest risk factor for both ischemic and haemorrhagic stroke with its incidence doubling for each successive decade after the age of fifty-five years. However, there is a substantial portion of patients with significant cerebrovascular disease who do not have any of these stroke risk-factors, leading to the speculation that there are other factors that have not been identified yet So as to improve diagnosis and treatment strategies, as well as to reduce the related public health burden, it could be helpful to successfully identify its extremely complex genetic determinants (polygenic, multiple genes play a role). Pharmacogenetics is the field of pharmacology that deals with the influence of genetic variation on drug response by correlating gene expression and gene variants with the efficacy or toxicity of drugs. The principle drugs in stroke medicine are antithrombotics. The aim of this paper was to review the most commonly used drugs for stroke such as rtPA in the acute phase as well as antiplatelets and wafarin for secondary prophylaxis.

LDL and HDL subclasses in acute ischemic stroke: prediction of risk and short-term mortality

OBJECTIVE

Small, dense low-density lipoprotein (sdLDL) and small-sized high-density lipoprotein (HDL) particles are established risk factors for ischemic heart disease. However, their clinical significance for acute ischemic stroke (AIS) is uncertain. This study evaluates associations of LDL and HDL particle sizes and subclasses with AIS risk and short-term mortality after AIS.

METHODS

Two hundred AIS patients hospitalised for first-in-a-lifetime stroke and 162 apparently healthy controls were included in the study. LDL and HDL particles were separated by gradient gel electrophoresis and serum lipid parameters were measured by standard laboratory methods. Baseline characteristics of LDL and HDL particles were evaluated for the prediction of AIS and short-term mortality after AIS.

RESULTS

AIS patients had significantly more LDL III and IVb, but less LDL I and II particles. They also had significantly smaller HDL size, more HDL 3a, 3b and 3c and less HDL 2b subclasses. The relative content of both sdLDL and small-sized HDL particles was significantly increased in patients (P<0.001 and P<0.001, respectively). In addition, sdLDL was significantly higher in AIS fatalities (n=25) compared with survivors (n=175, P<0.05). Increased sdLDL was a significant predictor of AIS (OR=4.31; P<0.001) and in-hospital mortality after AIS (OR=5.50; P<0.05). The observed relationships persisted after adjustment for conventional risk factors.

CONCLUSIONS

AIS is associated with adverse distributions of LDL and HDL subclasses. In addition, short-term mortality after AIS is associated with increased sdLDL particles. Our results indicate that sdLDL is an independent predictor of both AIS onset and consecutive short-term mortality.

Is inequality at the heart of it? Cross-country associations of income inequality with cardiovascular diseases and risk factors

Despite a number of cross-national studies that have examined the associations between income inequality and broad health outcomes such as life expectancy and all-cause mortality, investigations of the cross-country relations between income inequality and cardiovascular disease (CVD) morbidity, mortality, and risk factors are sparse. We analyzed the cross-national relations between income inequality and age-standardized mean body mass index (BMI), serum total cholesterol, systolic blood pressure (SBP), obesity prevalence, smoking impact ratio (SIR), and age-standardized and age-specific disability-adjusted life-years (DALYs) and mortality rates from coronary heart disease (CHD) and stroke, controlling for multiple country-level factors and specifying 5- to 10-year lag periods. In multivariable analyses primarily limited to industrialized countries, countries in the middle and highest (vs. lowest) tertiles of income inequality had higher absolute age-standardized obesity prevalences in both sexes. Higher income inequality was also related to higher mean SBP in both sexes, and higher SIR in women. In analyses of larger sets of countries with available data, positive associations were observed between higher income inequality and mean BMI, obesity prevalence, and CHD DALYs and mortality rates. Associations with stroke outcomes were inverse, yet became positive with the inclusion of eastern bloc and other countries in recent economic/political transition. China was also identified to be an influential data point, with the positive associations with stroke mortality rates becoming attenuated with its inclusion. Overall, our findings are compatible with harmful effects of income inequality at the national scale on CVD morbidity, mortality, and selected risk factors, particularly BMI/obesity. Future studies should consider income inequality as an independent contributor to variations in CVD burden globally.

Efficacy and safety of chunghyul-dan (qingwie-dan) in patients with hypercholesterolemia

Chunghyul-dan has inhibitory effects on HMG-CoA reductase and pancreatic lipase. We investigated whether Chunghyul-dan has therapeutic effects on humans with hypercholesterolemia. This study was a case-control, open-labeled clinical study. Subjects were treated with Chunghyul-dan (600 mg/day) or Atorvastatin (10 mg/day) for 8 weeks. Serum lipids were checked at baseline after 4 and 8 weeks of medication. While, Chunghyul-dan showed significant lipid-lowering effects, it was less effective than Atorvastatin. In comparison with the histological controls, Chunghyul-dan's effects were superior to placebo. On safety assessment, there was no adverse effect with the use of Chunghyul-dan in hepatic or renal toxicity. In conclusion, we suggest that Chunghyul-dan is a useful herbal medicine for hypercholesterolemia.

Evidence from biomarkers and surrogate endpoints

The use of physiological, anatomical, and other biological tests is commonplace in the practice of medicine. In neurology, objectively measured tests termed biomarkers (BMs) are playing an increasing role in diagnosis and management of disease, both in clinical practice and in experimental therapeutics. This article will discuss the various applications of BMs to the assessment of therapies for neurological diseases and will use examples from neurological diseases to elucidate the strengths and potential weaknesses of BMs. As the understanding of the pathophysiology of many neurological diseases has improved, new BMs have been developed, and efforts have been made to use these as proxies for clinical endpoints. A BM used in this manner is referred to as a surrogate endpoint (SE). There are many potential advantages and disadvantages of using SEs in the evaluation of new therapies, and these will be reviewed as well. Furthermore, the evidence required for the development of an SE and the nature of the evidence that can be derived from the use of BMs and SEs will be discussed.

New and emerging data from clinical trials of statins

Recent clinical trials of statins have clearly demonstrated the benefit of statin therapy in preventing both coronary and cerebral vascular events. These benefits have been demonstrated to be present without reference to older age, sex, or comorbid conditions, including hypertension and diabetes. Future trials will test the value of more aggressive low-density lipoprotein cholesterol lowering, the value of immediate statin intervention during acute coronary syndromes, the role of cholesterol lowering with or without angioplasty, and the role of cholesterol lowering in stroke prevention.

Cholesterol in neurologic disorders of the elderly: stroke and Alzheimer’s disease

Mechanisms for the regulation of intracellular cholesterol levels in various types of brain and vascular cells are of considerable importance in our understanding of the pathogenesis of a variety of diseases, particularly atherosclerosis and Alzheimer's disease (AD). It is increasingly clear that conversion of brain cholesterol into 24-hydroxycholesterol and its subsequent release into the periphery is important for the maintenance of brain cholesterol homeostasis. Recent studies have shown elevated plasma concentrations of 24-hydroxycholesterol in patients with AD and vascular dementia, suggesting increased brain cholesterol turnover during neurodegeneration. The oxygenases involved in the degradation and excretion of cholesterol, including the cholesterol 24-hydroxylase and the 27-hydroxylase, are enzymes of the cytochrome P-450 family. This review focuses on the newly recognized importance of cholesterol and its oxygenated metabolites in the pathogenesis of ischemic stroke and AD. The reduction in stroke and AD risk in patients treated with cholesterol-lowering statins is also discussed.

IGF-I activity may be a key determinant of stroke risk--a cautionary lesson for vegans

IGF-I acts on vascular endothelium to activate nitric oxide synthase, thereby promoting vascular health; there is reason to believe that this protection is especially crucial to the cerebral vasculature, helping to ward off thrombotic strokes. IGF-I may also promote the structural integrity of cerebral arteries, thereby offering protection from hemorrhagic stroke. These considerations may help to explain why tallness is associated with low stroke risk, whereas growth hormone deficiency increases stroke risk--and why age-adjusted stroke mortality has been exceptionally high in rural Asians eating quasi-vegan diets, but has been declining steadily in Asia as diets have become progressively higher in animal products. There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat--both characteristic of those adopting low-fat vegan diets--may also increase stroke risk. Vegans are thus well advised to adopt practical countermeasures to minimize stroke risk--the most definitive of which may be salt restriction. A high potassium intake, aerobic exercise training, whole grains, moderate alcohol consumption, low-dose aspirin, statin or policosanol therapy, green tea, and supplementation with fish oil, taurine, arginine, and B vitamins--as well as pharmacotherapy of hypertension if warranted--are other practical measures for lowering stroke risk. Although low-fat vegan diets may markedly reduce risk for coronary disease, diabetes, and many common types of cancer, an increased risk for stroke may represent an 'Achilles heel'. Nonetheless, vegans have the potential to achieve a truly exceptional 'healthspan' if they face this problem forthrightly by restricting salt intake and taking other practical measures that promote cerebrovascular health.

What do the statins tell us?

Until the recent introduction of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), the potential effect of cholesterol lowering on the prevention of clinical manifestations of coronary disease was a matter of debate. In trials conducted before the introduction of statins, cholesterol levels were lowered, on average, by only approximately 10%, resulting in prevention of coronary events but with no effect on total mortality rates. However, statins have been able to reduce low-density lipoprotein cholesterol levels by a mean of roughly 28%, significantly decreasing both relative and absolute risk levels of coronary events and total mortality. These benefits have been demonstrated not only in middle-aged men but also in women and patients aged >65 years. Aggressive cholesterol lowering has also been shown to yield larger decreases in the incidence of subsequent coronary events than angioplasty, and to reduce the occurrence of such events in patients who have undergone coronary artery bypass graft surgery, which raises the question of whether these procedures should be relegated to symptom relief, with cholesterol lowering as the primary means of coronary heart disease event prevention. Statins, therefore, have unequivocally shown the importance of cholesterol lowering in the prevention of morbidity and mortality due to coronary disease. Ongoing research will elucidate the role of statin therapy in the prevention of strokes and in the treatment of patients aged >75 years, and future trials will be needed to evaluate the potential role of statins in primary prevention for younger populations who cannot control cholesterol with lifestyle changes.