Cognitive correlates of cerebral white matter changes

White matter hyperintensities and risks of cognitive impairment and dementia: A systematic review and meta-analysis of 36 prospective studies

BACKGROUND

White matter hyperintensities of presumed vascular origin (WMH) are one of the imaging features of cerebral small vessel disease. Controversies persist about the effects of WMH on cognitive dysfunction. This meta-analysis aimed to identify the associations of WMH with risks of cognitive impairment and dementia.

METHODS

We searched PubMed, EMBASE and Cochrane Library for prospective studies. Primary analyses of cognitive dysfunction and sub-analyses of specific outcomes and study characteristics were conducted using random-effect models.

RESULTS

Thirty-six prospective studies with 19,040 participants were included. WMH at baseline conferred a 14 % elevated risk of cognitive impairment and all-cause dementia (ACD). WMH also conferred 25 % elevated risk of Alzheimer's disease and 73 % elevated risk of vascular dementia. Risk effects of high-grade WMH and continually increasing WMH (in volume or severity) on ACD were revealed. Periventricular WMH conferred a 1.51-fold excess risk for dementia.

CONCLUSIONS

WMH were associated with increased risk of cognitive dysfunction and could become a neuroimaging indicator of dementia.

Association between neurological disorders, functioning, and mortality in the elderly

OBJECTIVES

In aging populations, the prevalence of neurological disorders increases, which imposes high population burden in terms of mortality, disability, and impaired quality of life. The aim of this study was to assess the prevalence of common neurological disorders and signs and their association with functioning and mortality in an elderly general population.

MATERIALS AND METHODS

We used data from the Memory and Morbidity in Augsburg Elderly (MEMO) project, a population-based study of 385 individuals aged ≥65. The prevalence of neurological disorders and signs was assessed by physical examination and medical interview. The basic and instrumental activities of daily living were assessed (ADL, IADL). We assessed the association of neurological disorders and signs with everyday functioning and prospectively analyzed their relationship with mortality.

RESULTS

We observed considerably impaired functioning for cases with stroke, TIA, PD, and mild motor parkinsonian signs (MMPS). All-cause mortality was significantly increased in participants with stroke and MMPS, even after adjusting for co-variables (HR = 2.71 and 1.80, respectively).

CONCLUSIONS

We found that not only specific neurological disorders, but also earlier symptoms are related to impaired functioning and predict mortality in the elderly. These findings have potential clinical relevance for screening and early detection of individuals at risk.

Structural imaging measures of brain aging

During the course of normal aging, biological changes occur in the brain that are associated with changes in cognitive ability. This review presents data from neuroimaging studies of primarily "normal" or healthy brain aging. As such, we focus on research in unimpaired or nondemented older adults, but also include findings from lifespan studies that include younger and middle aged individuals as well as from populations with prodromal or clinically symptomatic disease such as cerebrovascular or Alzheimer's disease. This review predominantly addresses structural MRI biomarkers, such as volumetric or thickness measures from anatomical images, and measures of white matter injury and integrity respectively from FLAIR or DTI, and includes complementary data from PET and cognitive or clinical testing as appropriate. The findings reveal highly consistent age-related differences in brain structure, particularly frontal lobe and medial temporal regions that are also accompanied by age-related differences in frontal and medial temporal lobe mediated cognitive abilities. Newer findings also suggest that degeneration of specific white matter tracts such as those passing through the genu and splenium of the corpus callosum may also be related to age-related differences in cognitive performance. Interpretation of these findings, however, must be tempered by the fact that comorbid diseases such as cerebrovascular and Alzheimer's disease also increase in prevalence with advancing age. As such, this review discusses challenges related to interpretation of current theories of cognitive aging in light of the common occurrence of these later-life diseases. Understanding the differences between "Normal" and "Healthy" brain aging and identifying potential modifiable risk factors for brain aging is critical to inform potential treatments to stall or reverse the effects of brain aging and possibly extend cognitive health for our aging society.

Cognition and Hemodynamics

The relationship between cerebral hemodynamics and cognitive performance has increasingly become recognized as a major challenge in clinical practice for older adults. Both diabetes and hypertension worsen brain perfusion and are major risk factors for cerebrovascular disease, stroke and dementia. Cerebrovascular reserve has emerged as a potential biomarker for monitoring pressure-perfusion-cognition relationships. Endothelial dysfunction and inflammation, microvascular disease, and mascrovascular disease affect cerebral hemodynamics and play an important role in pathohysiology and severity of multiple medical conditions, presenting as cognitive decline in the old age. Therefore, the identification of cerebrovascular vascular reactivity as a new therapeutic target is needed for prevention of cognitive decline late in life.

Association between white matter microstructure, executive functions, and processing speed in older adults: the impact of vascular health

Cerebral white matter damage is not only a commonly reported consequence of healthy aging, but is also associated with cognitive decline and dementia. The aetiology of this damage is unclear; however, individuals with hypertension have a greater burden of white matter signal abnormalities (WMSA) on MR imaging than those without hypertension. It is therefore possible that elevated blood pressure (BP) impacts white matter tissue structure which in turn has a negative impact on cognition. However, little information exists about whether vascular health indexed by BP mediates the relationship between cognition and white matter tissue structure. We used diffusion tensor imaging to examine the impact of vascular health on regional associations between white matter integrity and cognition in healthy older adults spanning the normotensive to moderate-severe hypertensive BP range (43-87 years; N = 128). We examined how white matter structure was associated with performance on tests of two cognitive domains, executive functioning (EF) and processing speed (PS), and how patterns of regional associations were modified by BP and WMSA. Multiple linear regression and structural equation models demonstrated associations between tissue structure, EF and PS in frontal, temporal, parietal, and occipital white matter regions. Radial diffusivity was more prominently associated with performance than axial diffusivity. BP only minimally influenced the relationship between white matter integrity, EF and PS. However, WMSA volume had a major impact on neurocognitive associations. This suggests that, although BP and WMSA are causally related, these differential metrics of vascular health may act via independent pathways to influence brain structure, EF and PS.

The relationship between blood pressure and cognitive function

The relationship between blood pressure (BP) and cognitive outcomes in elderly adults has implications for global health care. Both hypertension and hypotension affect brain perfusion and worsen cognitive outcomes. The presence of hypertension and other vascular risk factors has been associated with decreased performance in executive function and attention tests. Cerebrovascular reserve has emerged as a potential biomarker for monitoring pressure-perfusion-cognition relationships. A decline in vascular reserve capacity can lead to impaired neurovascular coupling and decreased cognitive ability. Endothelial dysfunction, microvascular disease, and mascrovascular disease in midlife could also have an important role in the manifestations and severity of multiple medical conditions underlying cognitive decline late in life. However, questions remain about the role of antihypertensive therapies for long-term prevention of cognitive decline. In this Review, we address the underlying pathophysiology and the existing evidence supporting the role of vascular factors in late-life cognitive decline.

Hypertension and cerebral diffusion tensor imaging in small vessel disease

BACKGROUND AND PURPOSE

Hypertension is a risk factor for cerebral small vessel disease, which includes white matter lesions (WML) and lacunar infarcts. These lesions are frequently observed on MRI scans of elderly people and play a role in cognitive decline. Preferably, one would like to evaluate the effect of hypertension before fluid-attenuated inversion recovery visible macrostructural lesions occur, possibly by investigating its effect on the microstructural integrity of the white matter. Diffusion tensor imaging provides measures of structural integrity.

METHODS

In 503 patients with small vessel disease, aged between 50 and 85 years, we cross-sectionally studied the relation between blood pressure, hypertension, and hypertension treatment status and diffusion tensor imaging parameters in both normal-appearing white matter (NAWM) and WMLs. All of the subjects underwent 1.5-T MRI and diffusion tensor imaging scanning. Fractional anisotropy and mean diffusivity were calculated in both NAWM and WMLs.

RESULTS

Increased blood pressure and hypertension were significantly related to lower fractional anisotropy in both NAWM and WMLs and to higher mean diffusivity in WMLs. For hypertensives, odds ratios for the risk of impaired microstructural integrity (fractional anisotropy) were 3.1 (95% CI: 1.8 to 5.7) and 2.1 (95% CI: 1.2 to 3.5) in NAWM and WMLs, respectively, compared with normotensives. Fractional anisotropy odds ratios for treated uncontrolled subjects were 6.5 (95% CI: 3.3 to 12.7) and 2.7 (95% CI: 1.5 to 5.1) in NAWM and WMLs, respectively, compared with normotensives.

CONCLUSIONS

Our data show that diffusion tensor imaging may be an appropriate tool to monitor the effect of blood pressure and the response to treatment on white matter integrity, probably even before the development of WMLs on fluid-attenuated inversion recovery.

Association between white matter hyperintensities and executive decline in mild cognitive impairment is network dependent

White matter hyperintensities (WMH) in Mild Cognitive Impairment (MCI) have been associated with impaired executive functioning, although contradictory findings have been reported. The aim of this study was to examine whether WMH location influenced the relation between WMH and executive functioning in MCI participants (55-90 years) in the European multicenter memory-clinic-based DESCRIPA study, who underwent MRI scanning at baseline (N = 337). Linear mixed model analysis was performed to test the association between WMH damage in three networks (frontal-parietal, frontal-subcortical and frontal-parietal-subcortical network) and change in executive functioning over a 3-year period. WMH in the frontal-parietal and in the frontal-parietal-subcortical network were associated with decline in executive functioning. However, the frontal-subcortical network was not associated with change in executive functioning. Our results suggest that parietal WMH are a significant contributor to executive decline in MCI and that investigation of WMH in the cerebral networks supporting cognitive functions provide a new way to differentiate stable from cognitive declining MCI individuals.

Comparing Cerebral White Matter Lesion Burdens between Parkinson's Disease with and without Dementia

Cerebral white matter lesions (CWMLs) have been suggested to be associated with an increased risk of dementia, disability, and death. CWMLs are more common in individuals with Alzheimer's disease (AD) than in normal elderly individuals of comparable age. Only a few studies have been done to determine whether CWMLs may influence cognitive decline in Parkinson's disease (PD). Fully developed PD with concurrent AD was reported to likely cause impaired cognition in spite of accumulating evidence suggesting that PD with dementia (PDD) is more closely associated with Lewy body (LB) pathology. Currently, contradictory data on the neuropathology of dementia in PD require further prospective clinicopathological studies in larger cohorts to elucidate the impact of AD and α-synuclein (SCNA) pathologies on the cognitive status in these disorders. Previous reports did not suggest CWMLs to be associated with an increased risk of PDD. After adjusting for age at death, age at onset of PD, and duration of PD, our recent study investigating CWMLs in PDD via autopsy has shown a positive correlation between the burden of CWMLs and PDD. The frequent co-existence of both LB and AD lesions suggests that both pathologies independently or synergistically contribute to both movement disorders and cognitive impairment. The individual and cumulative burden of CWMLs, LB lesions, and AD lesions may synergistically contribute to cognitive decline in LB disorders such as PDD.

Atrial fibrillation is associated with lower cognitive performance in the Framingham offspring men

The purpose of this study was to investigate the association of atrial fibrillation (AFIB) with multiple measures of cognitive performance in a large community-based sample extensively characterized for vascular risk factors. Our primary analysis included 1011 Framingham Offspring Study (Framingham, Mass) men, mean age = 61.0 (37-89) years, free of clinical stroke and dementia. Using multivariable linear regression models, we related the presence (n = 59) versus absence (n = 952) of AFIB in men to a global measure of performance and multiple measures of specific cognitive abilities assessed an average of 8 months after the AFIB surveillance period. Adjusting for age, education, multiple cardiovascular risk factors, and cardiovascular disease, men with AFIB exhibited significantly lower mean levels of cognitive performance compared with men in normal sinus rhythm. Men with AFIB exhibited lower performance on global cognitive ability and cognitive abilities including Similarities (abstract reasoning), Visual Reproductions-Immediate Recall, Visual Reproductions-Delayed Recall, Visual Organization, Logical Memory-Delayed Recall, and Trail Making A (scanning and tracking) and Trail Making B (scanning, tracking, and executive functioning). Further studies leading to a better understanding of the mechanisms underlying the relation between AFIB and cognitive performance are important.

Chronic ischemia and neurocognition

Cognitive impairment from a major stroke as a consequence of carotid disease is an acknowledged clinical outcome; however, cognitive impairment without major stroke is open to discussion. The three recognized mechanisms for cognitive dysfunction from internal carotid artery are microembolization, white-matter disease, and hypoperfusion. The last has been most difficult to characterize physiologically. In this article, the authors review evidence supporting the existence of chronic ischemia in the brain and its direct impact on cognitive functions. By incorporating the pathophysiology of chronic ischemia into the algorithm of the management of carotid artery disease, we may be able to extend the goals of carotid artery revascularization beyond merely preventing stroke to include preventing or reversing cognitive decline.

Quantifying degeneration of white matter in normal aging using fractal dimension

Although degeneration of brain white matter (WM) in aging is a well-recognized problem, its quantification has mainly relied on volumetric measurements, which lack detail in describing the degenerative adaptation. In this study, WM structural complexity was evaluated in healthy old and young adults by analyzing the three-dimensional fractal dimension (FD) of WM segmented from magnetic resonance images of brain. FDs detected in the old were significantly smaller than in the young subjects. Specifically, WM interior structure complexity degenerated in the left hemisphere in old men but in the right hemisphere in old women. Men showed more complex WM patterns than women. An asymmetrical (right-greater-than-left-hemisphere) complexity pattern was observed in the interior and general structures of WM, yet the surface complexity was symmetrical across WM structures of the two hemispheres. WM volumes were also measured, but no significant decline was found with aging. These results suggest that the deterioration of WM complexity is not uniformly distributed between the genders and across brain hemispheres.

Brain tissue volumes and small vessel disease in relation to the risk of mortality

Brain atrophy and small vessel disease increase the risk of dementia and stroke. In a population-based cohort study (n=490; 60-90 years) we investigated how volumetric measures of atrophy and small vessel disease were related to mortality and whether this was independent of incident dementia or stroke. Brain volume and hippocampal volume were considered as measures of atrophy, whereas white matter lesions (WML) and lacunar infarcts reflected small vessel disease. We first investigated all-cause mortality in the whole cohort. In subsequent analyses we censored persons at incident dementia or incident stroke. Finally, we separately investigated cardiovascular mortality. The average follow-up was 8.4 years, during which 191 persons died. Brain atrophy and hippocampal atrophy, as well as WML increased the risk of death. The risks associated with hippocampal atrophy attenuated when censoring persons at incident dementia, but not at incident stroke. Censoring at either incident dementia or stroke did not change the risk associated with brain atrophy and WML. Moreover, WML were particularly associated with cardiovascular mortality.

Extent and distribution of white matter hyperintensities in normal aging, MCI, and AD

OBJECTIVE

To analyze the extent and spatial distribution of white matter hyperintensities (WMH) in brain regions from cognitively normal older individuals (CN) and patients with mild cognitive impairment (MCI) and Alzheimer disease (AD).

METHODS

We studied 26 mild AD, 28 MCI, and 33 CN. MRI analysis included quantification of WMH volume, nonlinear mapping onto a common anatomic image, and spatial localization of each WMH voxel to create an anatomically precise frequency distribution map. Areas of greatest frequency of WMH from the WMH composite map were used to identify 10 anatomic regions involving periventricular areas and the corpus callosum (CC) for group comparisons.

RESULTS

Total WMH volumes were associated with age, extent of concurrent vascular risk factors, and diagnosis. After correcting for age, total WMH volumes remained significantly associated with diagnosis and extent of vascular risk. Regional WMH analyses revealed significant differences in WMH across regions that also differed significantly according to diagnosis. In post-hoc analyses, significant differences were seen between CN and AD in posterior periventricular regions and the splenium of the CC. MCI subjects had intermediate values at all regions. Repeated measures analysis including vascular risk factors in the model found a significant relationship between periventricular WMH and vascular risk that differed by region, but regional differences according to diagnosis remained significant and there was no interaction between diagnosis and vascular risk.

CONCLUSIONS

Differences in white matter hyperintensities (WMH) associated with increasing cognitive impairment appear related to both extent and spatial location. Multiple regression analysis of regional WMH, vascular risk factors, and diagnosis suggest that these spatial differences may result from the additive effects of vascular and degenerative injury. Posterior periventricular and corpus callosum extension of WMH associated with mild cognitive impairment and Alzheimer disease indicate involvement of strategic white matter bundles that may contribute to the cognitive deficits seen with these syndromes.

Advances in white matter imaging: a review of in vivo magnetic resonance methodologies and their applicability to the study of development and aging

Several newer magnetic resonance imaging (MRI) techniques are increasingly being applied to the study of white matter development and pathology across the lifespan. These techniques go beyond traditional macrostructural volumetric methods and provide valuable information about underlying tissue integrity and organization at the microstructural and biochemical levels. We first provide an overview of white matter development and discuss the role of white matter and myelin in cognitive function. We also review available studies of development that have employed traditional volumetric measures. Then, we discuss the contributions of four newer imaging paradigms to our understanding of brain development and aging. These paradigms are Diffusion Tensor Imaging (DTI), Magnetization Transfer Imaging (MTI), T2-Relaxography, and Magnetic Resonance Spectroscopy (MRS). Studies examining brain development during childhood and adulthood as well as studies of the effects of aging are discussed.

A three-dimensional fractal analysis method for quantifying white matter structure in human brain

Fractal dimension (FD) is increasingly used to quantify complexity of brain structures. Previous research that analyzed FD of human brain mainly focused on two-dimensional measurements. In this study, we developed a three-dimensional (3D) box-counting method to measure FD of human brain white matter (WM) interior structure, WM surface and WM general structure simultaneously. This method, which firstly incorporates a shape descriptor (3D skeleton) representing interior structure and combines the three features, provides a more comprehensive characterization of WM structure. WM FD of different brain segments was computed to test robustness of the method. FDs of fractal phantoms were computed to test the accuracy of the method. The consistency of the computed and theoretical FD values suggests that our method is accurate in measuring FDs of fractals. Statistical analysis was performed to examine sensitivity of the method in detecting WM structure differences in a number of young and old subjects. FD values of the WM skeleton and surface were significantly greater in young than old individuals, indicating more complex WM structures in young people. These results suggest that our method is accurate in quantifying three-dimensional brain WM structures and sensitive in detecting age-related degeneration of the structures.

Risk of falls in Alzheimer's disease: a prospective study

OBJECTIVE

Falls are common in patients with Alzheimer's disease (AD). Identification of the potential risk factors and developing preventive strategies for falls will have a significant impact in maintaining the quality of life in AD.

PATIENTS

Clinical follow-up of 124 (74.1+/-6.1 years, range 62-88) mild to moderate AD patients in an outpatient memory clinic.

METHODS

Postural sway, cognitive function, use of neuroleptics, severity of periventricular and deep white matter lesions, and the presence or absence of silent brain infarctions on magnetic resonance imaging were assessed at baseline.

RESULTS

A total of 104 patients (84%) completed the study. Fall events were confirmed in 42.3% (44/104). After adjustment for age, gender, and cognitive status, a high grade of periventricular white matter lesions (odds ratio 8.7 [95%CI 1.5 to 51.8], p = 0.017) and neuroleptic drug use (odds ratio 3.5 [95%CI 1.2 to 10.5], p = 0.027) were significantly associated with an increased risk of falls.

CONCLUSION

Our results suggest that periventricular white matter lesions and the use of neuroleptics may be related to falls in mild to moderate AD. A comprehensive risk management of brain ischemia as well as the use of the smallest efficacious dose of neuroleptics in the treatment of behavioral and psychiatric symptoms of AD should be recommended to help reduce the risk of unexpected falls.

The role of cerebrovascular disease in dementia

BACKGROUND

Improvements in health care over the last 50 years have lengthened average life expectancy significantly, resulting in considerable growth of the population over 65 years of age. With increased age, however, comes an increased risk for Alzheimer's disease (AD), and the prevalence of AD is predicted to reach epidemic proportions by the later half of the 21st century. The prevalence of cerebrovascular disease also increases with age, and recent evidence suggests that cerebrovascular risk factors such as hypertension and hypercholesterolemia also increase an individual's risk for AD, suggesting a potential interaction between these two very common disorders. The potential impact of cerebrovascular disease on general cognitive health is not yet well understood, but is now being actively explored and clarified.

REVIEW SUMMARY

Cerebrovascular disease may manifest itself in many ways, and this review begins by discussing the possible spectrum of brain injury associated with common cerebrovascular risk factors. The prominent role of brain imaging to detect clinically silent cerebrovascular disease is recognized and reviewed. The neuropsychological consequences of cerebrovascular disease across the cognitive spectrum is also reviewed, including potential mechanisms by which cerebrovascular disease may interact with AD to increase the expression or hasten the progression of dementia.

CONCLUSIONS

Cerebrovascular risk factors, common to the elderly, lead to pernicious brain injury and subtle cognitive impairment that most probably places the individual at greater lifetime risk for dementia. The cause of dementia among individuals with cerebrovascular disease, however, remains AD. Recognition of the potential role of cerebrovascular disease as an independent risk factor for AD offers the possibility of primary prevention through treatment of well-recognized risk factors and deserves further study. In the meantime, clinicians presented with an individual suffering from a slowly progressive dementia and findings of clinically silent cerebrovascular brain injury should recognize the potential role of cerebrovascular disease in the dementia process but not ignore the likely overwhelming effects of AD and treat appropriately.

Prognostic significance of white matter changes in a memory clinic population

Non-specific white matter changes (WMC) can be seen on neuroimaging of the brain in healthy elderly but are more common in dementia. WMC are correlated to specific cognitive deficits and might also contribute to global cognitive decline. The value of WMC as a predictor of cognitive impairment has been incompletely elucidated. We studied the prognostic significance of extensive WMC in a group of patients with memory disturbances, to evaluate if the presence of such changes predicts a poorer outcome. We retrospectively selected a group of 24 patients with prominent WMC on magnetic resonance imaging (MRI) and with different grades of memory impairment. We matched each patient, with regard to age, education, length of follow-up, initial score on the Mini Mental State Examination (MMSE) and initial diagnosis, to a patient without white matter pathology. The matched pairs were evaluated and the decrease in MMSE score after follow-up (range 2-4 years) was used as the outcome measure. Results showed no difference in the decrease in MMSE score at follow-up between patients with or without WMC. In conclusion, the presence of WMC in cognitively impaired patients had no effect on the progression rate of dementia, as measured by MMSE decline.

Brain white matter lesions detected by magnetic resonance [correction of resosnance] imaging are associated with balance and gait speed

OBJECTIVE

To investigate the relations between premorbid and current mental ability, mood, and white matter signal abnormalities detected by T2 weighted brain magnetic resonance imaging (MRI) and impairment of balance and mobility in older adults.

METHODS

97 subjects from the Aberdeen 1921 birth cohort underwent brain MRI, evaluation of balance, and measurement of gait speed. White matter hyperintensities detected on T2 weighted MRI scans were rated by three independent raters on three variables: white matter lesions; periventricular lesions; and brain stem lesions.

RESULTS

Decreased gait speed was correlated with impaired visual acuity (p = 0.020), shorter stature (p = 0.008), a lower childhood IQ (p = 0.030), a lower current Raven's progressive matrices score (Raven score) (p < 0.001), a higher hospital anxiety and depression scale (HADS) score (p = 0.004), and an increased grade of brain stem lesions on MRI. Inability to balance was correlated with Raven score (p = 0.042), brain stem lesions (p = 0.003), white matter lesions (p = 0.003), and periventricular lesions (p = 0.038). Binary logistic regression identified brain stem lesions (odds ratio (OR) 0.22; 95% confidence interval 0.09 to 0.54) and HADS depression score (OR 0.75; 0.58 to 0.97) as the only significant associations with balance. Structural equation modelling detected an association between two latent traits representing white matter disease and an integrating function, respectively.

CONCLUSIONS

In this cohort, white matter lesions, periventricular lesions, and brain stem lesions were associated with impaired balance. Current mental ability was strongly related to gait speed. There appears to be a concordance between motor skills and intellect in old age, which is degraded by white matter disease.

Periventricular cerebral white matter lesions predict rate of cognitive decline

The prospect of declining cognitive functions is a major fear for many elderly persons. Cerebral white matter lesions, as commonly found with magnetic resonance imaging, have been associated with cognitive dysfunction in cross-sectional studies. Only a few longitudinal studies using small cohorts confirmed these findings. We examined the relation between severity of white matter lesions and cognitive decline over a nearly 10-year period in 563 elderly subjects sampled from the general nondemented Dutch population. Severity of white matter lesions was scored for periventricular and subcortical regions separately using an extensive semiquantitative scale. Cognitive function was measured by the Mini-Mental State Examination at regular time intervals during 1990 to 2000, and magnetic resonance imaging scans were made in 1995 to 1996. More severe white matter lesions were associated with more rapid cognitive decline over a mean follow-up period of 7.3 years (standard deviation, 1.5). After adjusting for age, gender, educational level, measures of depression, and brain atrophy and infarcts, subjects with severe periventricular white matter lesions experienced cognitive decline nearly three times as fast (0.28 Mini-Mental State Examination points/year [95% confidence interval, 0.20-0.36]) as the average (0.10 points/year [95% confidence interval, 0.09-0.11]). There was no independent relationship between severity of subcortical white matter lesions and rate of cognitive decline.

Hypertension and cerebral white matter lesions in a prospective cohort study

White matter lesions are frequently found on cerebral MRI scans of elderly people and are thought to be important in the pathogenesis of dementia. Hyper tension has been associated with the presence of white matter lesions but this has been investigated almost exclusively in cross-sectional studies. We studied prospectively the association of these lesions with the duration and treatment of hypertension. We randomly sampled 1077 subjects aged between 60 and 90 years from two prospective population-based studies. One-half of the study subjects had their blood pressure measured between 1975 and 1978 and the other half between 1990 and 1993. All subjects underwent 1.5 T MRI scanning; white matter lesions in the subcortical and periventricular regions were rated separately. Subjects with hypertension had increased rates of both types of white matter lesion. Duration of hypertension was associated with both periventricular and subcortical white matter lesions. This relationship was influenced strongly by age. For participants with >20 years of hypertension and aged between 60 and 70 years at the time of follow-up, the relative risks for subcortical and periventricular white matter lesions were 24.3 [95% confidence interval (CI) 5.1-114.8] and 15.8 (95% CI 3.4-73.5), respectively, compared with normotensive subjects. Subjects with successfully treated hypertension had only moderately increased rates of subcortical white matter lesions and periventricular white matter lesions (relative risk 3.3, 95% CI 1.3-8.4 and 2.6, 95% CI 1.0-6.8, respectively) compared with normotensive subjects. For poorly controlled hypertensives, these relative risks were 8.4 (95% CI 3.1-22.6) and 5.8 (95% CI 2.1-16.0), respectively. In conclusion, we found a relationship between long-standing hypertension and the presence of white matter lesions. Our findings are consistent with the view that effective treatment may reduce the rates of both types of white matter lesion. Adequate treatment of hypertension may therefore prevent white matter lesions and the associated cognitive decline.

Cerebrospinal fluid cytoskeleton proteins in patients with subcortical white-matter dementia

The cerebrospinal fluid (CSF) levels of two cytoskeleton proteins, tau and the light subunit of neurofilament protein (NFL), both considered to reflect cerebral white-matter components, were investigated in a group of patients with a subtype of vascular dementia called 'subcortical white-matter dementia' (SWD). The group consisted of 25 demented patients with frontosubcortical brain syndromes, white-matter changes on computed tomography or magnetic resonance imaging and vascular disease or pronounced vascular risk factors. CSF-NFL was increased, whereas CSF-tau was normal, suggesting a differential involvement of the cytoskeleton in this patient group. The albumin ratio and the apolipoproteinE4 (ApoE4) allele status were also investigated. The albumin ratio was increased, indicating damage to the vessel walls with breakdown of the blood-brain barrier. No relationship was found between ApoE4 alleles and CSF levels of tau or NFL in this patient group. Besides presenting original data, the disease status of SWD is also discussed.

Neuropsychologic correlates of brain white matter lesions depicted on MR images: 1921 Aberdeen Birth Cohort

PURPOSE

To examine relationships between brain white matter hyperintensities depicted at magnetic resonance (MR) imaging and performance on neuropsychologic tests in community-dwelling elderly adults.

MATERIALS AND METHODS

The 1921 Aberdeen Birth Cohort is a subsample of survivors of the Scottish Mental Survey of 1932 whose mental ability was tested at 11 years of age. Ninety-five of these subjects agreed to undergo brain MR imaging, an examination of general health, and a neuropsychologic evaluation. White matter hyperintensities detected at T2-weighted MR imaging were rated by using a semiquantitative method yielding two continuous variables: white matter lesions and periventricular lesions. Cognitive ability, including crystallized and fluid intelligence domains, was assessed with standard neuropsychologic tests.

RESULTS

Rating scores of white matter lesions were normally distributed (on a devised scale) with means of 1.14 for white matter lesions and 1.28 for periventricular lesions. Intra- and interobserver reliability coefficients for scores were high, generally above 0.7. There were significant correlations of medium effect size between the T2-weighted MR imaging-depicted white matter lesions and performance on tests of fluid-type intelligence. No significant correlation was demonstrated between white matter lesion ratings and tests of crystallized intelligence.

CONCLUSION

Lower fluid-type ("prevailing") intelligence test scores were associated with increased severity of white matter lesion ratings but not crystallized-type ("premorbid") intelligence test scores. This indicates that MR imaging-depicted white matter lesions are of clinical importance.

Serum carotenoids and cerebral white matter lesions: the Rotterdam scan study

OBJECTIVES

To study the relation between serum levels of carotenoids and white matter lesions (WMLs) on magnetic resonance imaging (MRI).

DESIGN

Evaluation of cross-sectional data from a cohort study.

SETTING

The Rotterdam Scan Study.

PARTICIPANTS

Two hundred and three nondemented older persons, age 60 to 90, from the Rotterdam Scan Study.

MEASUREMENTS

Serum levels of carotenoids were determined. WMLs on MRIs were rated separately into periventricular and subcortical WMLs. Odds ratios (ORs) for the presence of severe WMLs (upper decile) were calculated per standard deviation (SD) increase in serum carotenoid level and per SD increase in overall carotenoid serum level. Effect modification by smoking status was studied through stratified analyses.

RESULTS

Increasing levels of all the separate carotenoids were associated with less severe periventricular WMLs, which reached statistical significance for the overall carotenoid serum level (OR 0.4 per SD; 95% confidence interval (CI) = 0.2-0.9). We found no association between carotenoid levels and the presence of severe subcortical WMLs (OR 1.2 per SD; 95% CI = 0.7-2.0). The association of carotenoid levels with severe periventricular WMLs was more marked in those who ever smoked (OR 0.1 per SD; 95% CI = 0.0-0.9) than in those who had never smoked (OR 0.9 per SD; 95% CI = 0.4-2.1).

CONCLUSIONS

These findings are compatible with the view that high levels of carotenoids may protect against WMLs in the periventricular region, in particular in smokers. Longitudinal studies with repeated measurements of both carotenoids and WMLs are necessary to explore this hypothesis further.

Prevalence of cerebral white matter lesions in elderly people: a population based magnetic resonance imaging study. The Rotterdam Scan Study

OBJECTIVE

White matter lesions are often seen on MR scans of elderly non-demented and demented people. They are attributed to degenerative changes of small vessels and are implicated in the pathogenesis of cognitive decline and dementia. There is evidence that especially periventricular white matter lesions are related to cognitive decline, whereas subcortical white matter lesions may be related to late onset depression. The frequency distribution of subcortical and periventricular white matter lesions according to age and sex reported.

METHODS

A total of 1077 subjects aged between 60-90 years were randomly sampled from the general population. All subjects underwent 1.5T MR scanning; white matter lesions were rated separately for the subcortical region and the periventricular region.

RESULTS

Of all subjects 8% were completely free of subcortical white matter lesions, 20% had no periventricular white matter lesions, and 5% had no white matter lesions in either of these locations. The proportion with white matter lesions increased with age, similarly for men and women. Women tended to have more subcortical white matter lesions than men (total volume 1.45 ml v 1. 29 ml; p=0.33), mainly caused by marked differences in the frontal white matter lesion volume (0.89 ml v 0.70 ml; p=0.08). Periventricular white matter lesions were also more frequent among women than men (mean grade 2.5 v 2.3; p=0.07). Also severe degrees of subcortical white matter lesions were more common in women than in men (OR 1.1; 95% confidence interval (95% CI) 0.8-1.5) and periventricular white matter lesions (OR 1.2; 95% CI 0.9-1.7), albeit that none of these findings were statistically significant.

CONCLUSIONS

The prevalence and the degree of cerebral white matter lesions increased with age. Women tended to have a higher degree of white matter lesions than men. This may underlie the finding of a higher incidence of dementia in women than in men, particularly at later age.

Aortic atherosclerosis at middle age predicts cerebral white matter lesions in the elderly

BACKGROUND AND PURPOSE

MRI scans of the brains of elderly people frequently show white matter lesions. Clinically, these lesions are associated with cognitive impairment and dementia. A relation between atherosclerosis and white matter lesions was found in some small cross-sectional studies. However, atherosclerosis is a gradual process that starts early in life. We investigated the longitudinal association between aortic atherosclerosis assessed during midlife and late life and cerebral white matter lesions.

METHODS

We randomly sampled subjects between 60 and 90 years old from 2 population-based follow-up studies in which subjects had their baseline examinations in 1975 to 1978 (midlife) and in 1990 to 1993 (late life). In 1995 to 1996, subjects underwent 1.5-T MRI scanning; white matter lesions were rated in the deep subcortical and periventricular regions separately. Aortic atherosclerosis was assessed on abdominal radiographs that were obtained from 276 subjects in midlife and 531 subjects in late life.

RESULTS

The presence of aortic atherosclerosis during midlife was significantly associated with the presence of periventricular white matter lesions approximately 20 years later (adjusted relative risk, 2.4; 95% CI, 1.2 to 5.0); the relative risks increased linearly with the severity of aortic atherosclerosis. No association was found between midlife aortic atherosclerosis and subcortical white matter lesions (adjusted relative risk, 1.1; 95% CI, 0.5 to 2.3) or between late-life aortic atherosclerosis and white matter lesions.

CONCLUSIONS

The pathogenetic process that leads to cerebral periventricular white matter lesions starts already in or before midlife. The critical period for intervention directed at prevention of white matter lesions and its cognitive consequences may be long before these lesions become clinically detectable.