Do risk factors for Alzheimer's disease predict dementia in Parkinson's disease? An exploratory study

Impact of tobacco smoking on disease-specific outcomes in common neurological disorders: A scoping review

Although the association of smoking with the risk of incident neurological disorders is well established, less is known about the impact of smoking and smoking cessation on outcomes of these conditions. The objective of this scoping review was to synthesize what is known about the impact of smoking and smoking cessation on disease-specific outcomes for seven common neurological disorders. We included 67 studies on the association of smoking and smoking cessation on disease-specific outcomes. For multiple sclerosis, smoking was associated with greater clinical and radiological disease progression, relapses, risk for disease-related death, cognitive decline, and mood symptoms, in addition to reduced treatment effectiveness. For stroke and transient ischemic attack, smoking was associated with greater rates of stroke recurrence, post-stroke cardiovascular outcomes, post-stroke mortality, post-stroke cognitive impairment, and functional impairment. In patients with cognitive impairment and dementia, smoking was associated with faster cognitive decline, and smoking was also associated with greater cognitive decline in Parkinson's disease, but not motor symptom worsening. Patients with amyotrophic lateral sclerosis who smoked faced increased mortality. Last, in patients with cluster headache, smoking was associated with more frequent and longer cluster attack periods. Conversely, for multiple sclerosis and stroke, smoking cessation was associated with improved disease-specific outcomes. In summary, whereas smoking is detrimentally associated with disease-specific outcomes in common neurological conditions, there is growing evidence that smoking cessation may improve outcomes. Effective smoking cessation interventions should be leveraged in the management of common neurological disorders to improve patient outcomes.

Short and Long-Term Cognitive Effects of Subthalamic Deep Brain Stimulation in Parkinson's Disease and Identification of Relevant Factors

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) successfully controls the motor symptoms of Parkinson's disease (PD) but has associated cognitive side-effects.

OBJECTIVE

Establish the short- and long-term cognitive effects of STN-DBS in PD.

METHODS

Both the short-term and long-term effects of STN-DBS on cognition were examined through evaluation of the controlled studies that compared patients with STN-DBS to unoperated PD patients, thus controlling for illness progression. We also reviewed the literature to identify the factors that influence cognitive outcome of STN-DBS in PD.

RESULTS

The meta-analysis of the short-term cognitive effects of STN-DBS revealed moderate effect sizes for semantic and phonemic verbal fluency and small effect sizes for psychomotor speed and language, indicating greater decline in the STN-DBS operated than the unoperated patients in these cognitive domains. The longer-term STN-DBS results from controlled studies indicated rates of cognitive decline/dementia up to 32%; which are no different from the rates from the natural progression of PD. Greater executive dysfunction and poorer memory pre-operatively, older age, higher pre-operative doses of levodopa, and greater axial involvement are some of the factors associated with worse cognition after STN-DBS in PD.

CONCLUSION

This evidence can be used to inform patients and their families about the short-term and long-term risks of cognitive decline following STN-DBS surgery and aid the team in selection of suitable candidates for surgery.

Valproate-associated Movement Disorder: A Literature Review

Valproate (VPA) was first synthesized in 1882, but it was only in the early 1960s that its anticonvulsant properties were discovered. The aim of this literature review is to evaluate the clinical epidemiological profile, pathological mechanisms, and management of VPA-associated movement disorder (MD). Relevant reports in six databases were identified and assessed by two reviewers without language restriction. A total of 138 reports containing 362 cases of subjects who developed a MD secondary to VPA were reported. The MD identified were parkinsonism (PKN) (252), myoclonus (MCL) (54), dystonia (DTN) (17), dyskinesia (DKN) (16), stutters (4), tics (3), akathisia (AKT) (1). In the not clearly defined group, 15 extrapyramidal symptoms, 3 AKT, 2 DTN, 1 rigidity, 1 unstable gait were assessed. The mean and median age was 55.8 (SD: 16.58) and 61 years (range: 4-87 years). The most common VPA-indication was epilepsy, and 51.36% were males. The mean and median time from the VPA start to the MD onset was 32.75 (SD: 30.05) and 21.15 months (range: 1 day - 20 years). The mean and median time from the VPA withdrawal until the MD recovery was 2.89 (SD: 2.79) and 3 months (1 day - 12 months). The most common management was drug withdrawal. A complete recovery was obtained in 80.61%. VPA-associated MD was extensively reported in the literature. PKN was the most well-described. Future studies need to clearly report the clinical history of the patient, considering the full investigation of other adverse events during their entire life.

Parkinsonism and dementia

The aim of the present review is to summarize literature data on dementia in parkinsonian disorders. Cognitive decline and the gradual development of dementia are considered to be key features in the majority of parkinsonian conditions. The burden of dementia in everyday life of parkinsonian patients and their caregivers is vast and can be even more challenging to handle than the motor component of the disease. Common pathogenetic mechanisms involve the aggregation and spreading of abnormal proteins like alpha-synuclein, tau or amyloid in cortical and subcortical regions with subsequent dysregulation of multiple neurotransmitter systems. The degree of cognitive deterioration in these disorders is variable and ranges from mild cognitive impairment to severe cognitive dysfunction. There is also variation in the number and type of affected cognitive domains which can involve either a single domain like executive or visuospatial function or multiple ones. Novel genetic, biological fluid or imaging biomarkers appear promising in facilitating the diagnosis and staging of dementia in parkinsonian conditions. A significant part of current research in Parkinson's disease and other parkinsonian syndromes is targeted towards the cognitive aspects of these disorders. Stabilization or amelioration of cognitive outcomes represents a primary endpoint in many ongoing clinical trials for novel disease modifying treatments in this field. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Cognition Deficits in Parkinson's Disease: Mechanisms and Treatment

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder mainly in middle-elderly population, which represents diverse nonmotor symptoms (NMS) besides such well-documented motor symptoms as bradykinesia, resting tremor, rigidity, and postural instability. With the advancement of aging trend worldwide, the global prevalence of PD is mounting up year after year. Nowadays, accumulating lines of studies have given a comprehensive and thorough coverage of motor symptoms in PD. Yet much less attention as compared has been paid to the nonmotor symptoms of PD, such as cognition deficits. Of note, a patient with PD who suffers from cognitive impairment may harbour a statistically significantly higher risk of progressing toward dementia, which negatively affects their life expectancy and daily functioning and overall lowers the global quality of life. Furthermore, it is a widely held view that cognitive dysfunction does not just occur in the late stage of PD. On the basis of numerous studies, mild cognitive impairment (MCI) is a harbinger of dementia in PD, which is observed as an intermediate state with considerable variability; some patients remain stable and some even revert to normal cognition. Considered that the timing, profile, and rate of cognitive impairment vary greatly among PD individuals, it is extremely urgent for researchers and clinicians alike to identify and predict future cognitive decline in this population. Simultaneously, early screening and canonical management of PD with cognitive deficits are very imperative to postpone the disease progression and improve the prognosis of patients. In our review, we focus on a description of cognitive decline in PD, expound emphatically the pathological mechanisms underlying cognition deficits in PD, then give a comprehensive overview of specific therapeutic strategies, and finally dissect what fresh insights may bring new exciting prospect for the subfield.

Modifiable risk factors for cognitive impairment in Parkinson's disease: A systematic review and meta-analysis of prospective cohort studies

BACKGROUND

Cognitive impairment is a common and devastating manifestation in Parkinson's disease (PD). We aimed to identify modifiable risk factors for PD with cognitive impairment.

METHODS

We systematically searched PubMed and the Cochrane Library from June 1937 to September 2018 and included prospective cohort studies with random-effects model used to combine estimates. Primary analyses for all types of cognitive impairments and subgroup analyses for separate outcomes were conducted.

RESULTS

A total of 31,298 articles were identified, of which 32 articles with 18 factors met the inclusion criteria for meta-analysis. In the primary analysis, 9 modifiable risk factors were found to increase the risk of PD with cognitive impairment, including postural-instability-gait disorder (relative risk = 3.76, 95% confidence interval = 1.36-10.40), hallucinations (relative risk = 3.09, 95% confidence interval = 1.61-5.93), orthostatic hypotension (relative risk = 2.98, 95% confidence interval = 1.41-6.28), cerebrovascular disease (relative risk = 1.52, 95% confidence interval = 1.01-2.28), diabetes mellitus (relative risk = 1.47, 95% confidence interval = 1.13-1.92), obesity (relative risk = 1.38, 95% confidence interval = 1.15-1.65), cardiac disease (relative risk = 1.35, 95% confidence interval = 1.17-1.56), alcohol consumption (relative risk = 1.32, 95% confidence interval = 1.15-1.52), and smoking (relative risk = 1.31, 95% confidence interval = 1.14-1.50). In the subgroup analysis, postural-instability-gait disorder subtype, orthostatic hypotension and hallucinations may increase the risk of dementia in PD. A total of 37 articles were included in the systematic review, in which 9 risk factors and 1 protective factor were additionally associated in single studies with the risk of PD with cognitive impairment, and 5 factors were associated with specific cognition domains.

CONCLUSIONS

Effective interventions in the management of PD symptoms, comorbidities, and lifestyles may be promising to reduce PD with cognitive impairment risk. © 2019 International Parkinson and Movement Disorder Society.

Risk of dementia after Parkinson's disease in Taiwan: a population-based retrospective cohort study using National Health Insurance claims

OBJECTIVES

A nationwide cohort study on the risk of dementia onset after first diagnosis of Parkinson's disease (PD) is lacking. This study aims to assess 11 years of incidence and the HRs for developing dementia in patients with PD compared with matched controls.

DESIGN

A population-based cohort study.

SETTING

National Health Insurance database in Taiwan.

PARTICIPANTS

A total of 5932 patients with PD were identified, and 29 645 age-matched, sex-matched and index year-matched PD-free individuals were randomly selected.

OUTCOME MEASURES

All subjects were linked to the claim data to identify the first diagnosis of dementia. The Poisson assumption was used to estimate the incidence rate. Cause-specific hazards models with a partitioning of time at 1 year to account for proportionality were used to estimate the risk of dementia onset.

RESULTS

The median duration from the first diagnosis of PD to the development of dementia was 9.02 years. In the first partition (≦ 1 year), the incidence of dementia in the PD and control groups was 114.49 and 9.76 per 1000 person-years, respectively, with an adjusted HR of 6.43 (95% CI 5.46 to 7.57). In the second partition (>1 year), the incidence of dementia in the PD and control groups was 30.99 and 10.83 per 1000 person-years, with an adjusted HR of 2.42 (95% CI 2.23 to 2.61). Notably, in the second partition, both men and women aged <70 years had the highest HR (3.82, 95% CI 2.79 to 5.22 and 4.27, 95% CI 3.25 to 5.63, respectively).

CONCLUSIONS

This study noted an increased risk of dementia after a diagnosis of PD. The magnitude of effect estimation was higher in men in the first partition but was similar in both genders in the second partition. PD patients aged <70 years have the highest risk of dementia in any given partition time.

Mind the gaps: What we don't know about cognitive impairment in essential tremor

INTRODUCTION

Although the hallmark feature of essential tremor (ET) is tremor, there is growing appreciation that cognitive impairment also occurs, including increased prevalence of mild cognitive impairment (MCI) and increased prevalence and incidence of dementia. With emerging knowledge of ET-cognitive impairment, come fundamental questions regarding its course, bases, predictors and clinical outcomes. Studies in the general population and in Parkinson's disease (PD), a related movement disorder, offer a starting point from which to begin filling these clinically important knowledge gaps.

METHODS

A PubMed search (June 2018) identified articles for this review.

RESULTS

Much of our knowledge of cognitive impairment in ET is of the static condition (e.g., prevalence of cognitive impairment in ET), with nearly no information on its bases, predictors and dynamics (i.e., course, and clinical outcomes). In PD, where such data have been published, rates of cognitive decline and conversion to MCI/dementia are higher than in the general population. Predictors of cognitive change in PD and the general population have also been identified, yet they only partially overlap one another.

CONCLUSION

The predictors and dynamics of cognitive impairment have been investigated fairly extensively in the general population, to a somewhat lesser extent in PD, and are emerging only now in ET. We suggest that longitudinal studies specific to ET are needed, and we outline variables to be considered in these investigations. Increased knowledge of ET-cognitive impairment will facilitate meaningful counseling of patients and their families.

Neuroprotective Actions of Glucagon-Like Peptide-1 (GLP-1) Analogues in Alzheimer's and Parkinson's Diseases

The current absence of effective treatments for Alzheimer's disease (AD) and Parkinson's disease (PD) reflects an incomplete knowledge of the underlying disease processes. Considerable efforts have been made to investigate the central pathological features of these diseases, giving rise to numerous attempts to develop compounds that interfere with such features. However, further characterization of the molecular targets within the interconnected AD and PD pathways is still required. Impaired brain insulin signaling has emerged as a feature that contributes to neuronal dysfunction in both AD and PD, leading to strategies aiming at restoring this pathway in the brain. Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for treatment of type 2 diabetes mellitus have been tested and have shown encouraging protective actions in experimental models of AD and PD as well as in initial clinical trials. We review studies revealing the neuroprotective actions of GLP-1 analogues in pre-clinical models of AD and PD and promising results from recent clinical trials.

The clinical characteristics and cognitive features of mild cognitive impairment in Parkinson's disease and the analysis of relevant factors

The purpose of this work is to investigate the clinical characteristics, cognitive impairment features, and subgroup types of Parkinson's disease (PD) subjects with mild cognitive impairment (PD-MCI) in the Chinese population and to analyze relevant risk factors for PD-MCI. A total of 234 non-dementia PD subjects were collected. Standardized neuropsychological assessments of overall cognitive level and four cognitive domains (memory, executive function, attention and visuospatial function) were performed using MDS Task Force diagnostic criteria for PD-MCI. PD-MCI subjects were further divided into four subgroups: nonamnestic single-domain impairment type (PD-naMCI-SD), nonamnestic multiple-domain impairment type (PD-naMCI-MD), amnestic single-domain impairment type (PD-aMCI-SD), and amnestic multiple-domain impairment type (PD-aMCI-MD). The clinical characteristics of and risk factors for all subgroups were analyzed. PD-MCI was found in 45.3% of the non-dementia PD subjects. Differences between the PD-MCI and PD with normal cognition groups with respect to age, age of onset, years of education, and motor symptom severity were significant (P < 0.05). The single-domain impairment type was the largest PD-MCI subgroup (52.83%). Memory and executive function impairment were most frequent (22.64% and 20.75%, respectively). Among the four subgroups, the number of years of education was significantly different (P = 0.003). The overall cognitive function in amnestic multiple-domain impairment type was significantly worse compared with that in those with single-domain impairment type. Regression analysis results showed that old age, high UPDRS-III score, and hyperhomocysteinemia were risk factors for PD-MCI, whereas high education level was a protective factor. Early prevention of MCI-related risk factors provides effective means to retard cognitive decline in PD patients.

Is traumatic brain injury a risk factor for neurodegeneration? A meta-analysis of population-based studies

Background

To determine the association of prior traumatic brain injury (TBI) with subsequent diagnosis of neurodegeneration disease.

Methods

All studies from 1980 to 2016 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, Embase, study references, and review articles. The data and study design were assessed by 2 investigators independently. A meta-analysis was performed by RevMan 5.3.

Results

There were 18 studies comprising 3,263,207 patients. Meta-analysis revealed a significant association of prior TBI with subsequent dementia. The pooled odds ratio (OR) for TBI on development of dementia, FTD and TDP-43 associated disease were 1.93 (95% CI 1.47–2.55, p < 0.001), 4.44 (95% CI 3.86–5.10, p < 0.001), and 2.97 (95% CI 1.35–6.53, p < 0.001). However, analyses of individual diagnoses found no evidence that the risk of Alzheimer’s disease, and Parkinson’s disease in individuals with previous TBI compared to those without TBI.

Conclusions

History of TBI is not associated with the development of subsequent neurodegeneration disease. Care must be taken in extrapolating from these results because no suitable criteria define post TBI neurodegenerative processes. Therefore, further research in this area is needed to confirm these questions and uncover the link between TBI and neurodegeneration disease.

The Therapeutic Potential of Metformin in Neurodegenerative Diseases

The search for treatments for neurodegenerative diseases is a major concern in light of today's aging population and an increasing burden on individuals, families, and society. Although great advances have been made in the last decades to understand the underlying genetic and biological cause of these diseases, only some symptomatic treatments are available. Metformin has long since been used to treat Type 2 Diabetes and has been shown to be beneficial in several other conditions. Metformin is well-tested in vitro and in vivo and an approved compound that targets diverse pathways including mitochondrial energy production and insulin signaling. There is growing evidence for the benefits of metformin to counteract age-related diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. We will discuss evidence showing that certain neurodegenerative diseases and diabetes are explicitly linked and that metformin along with other diabetes drugs can reduce neurological symptoms in some patients and reduce disease phenotypes in animal and cell models. An interesting therapeutic factor might be how metformin is able to balance survival and death signaling in cells through pathways that are commonly associated with neurodegenerative diseases. In healthy neurons, these overarching signals keep energy metabolism, oxidative stress, and proteostasis in check, avoiding the dysfunction and neuronal death that defines neurodegenerative disease. We will discuss the biological mechanisms involved and the relevance of neuronal vulnerability and potential difficulties for future trials and development of therapies.

The Therapeutic Potential of Metformin in Neurodegenerative Diseases

The search for treatments for neurodegenerative diseases is a major concern in light of today's aging population and an increasing burden on individuals, families, and society. Although great advances have been made in the last decades to understand the underlying genetic and biological cause of these diseases, only some symptomatic treatments are available. Metformin has long since been used to treat Type 2 Diabetes and has been shown to be beneficial in several other conditions. Metformin is well-tested in vitro and in vivo and an approved compound that targets diverse pathways including mitochondrial energy production and insulin signaling. There is growing evidence for the benefits of metformin to counteract age-related diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. We will discuss evidence showing that certain neurodegenerative diseases and diabetes are explicitly linked and that metformin along with other diabetes drugs can reduce neurological symptoms in some patients and reduce disease phenotypes in animal and cell models. An interesting therapeutic factor might be how metformin is able to balance survival and death signaling in cells through pathways that are commonly associated with neurodegenerative diseases. In healthy neurons, these overarching signals keep energy metabolism, oxidative stress, and proteostasis in check, avoiding the dysfunction and neuronal death that defines neurodegenerative disease. We will discuss the biological mechanisms involved and the relevance of neuronal vulnerability and potential difficulties for future trials and development of therapies.

Smoking history is associated to cognitive impairment in Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) are more likely to suffer from cognitive impairment and dementia than healthy older adults. The aim of this study was to investigate smoking history as a risk factor for cognitive decline in PD.

METHOD

One hundred thirty-nine PD patients aged 50 years and older (Hoehn and Yahr = 1-3) were recruited from a clinical database. Global cognitive function was assessed with the Mini-Mental State Examination (MMSE) and smoking history was investigated as part of a standard clinical interview. A multiple linear regression analysis was used to develop a model for predicting participants' MMSE scores from age, education, Hoehn and Yahr stage, disease duration, the number of vascular risk factors and the number of smoking pack-years.

RESULTS

The regression model significantly accounted for 22.9% of the variance in MMSE scores. Significant predictors were education (β = .312, p < .001), age (β = -.215, p = .013) and total smoking pack-years (β = -.180, p = .029). In former smokers, the number of years since quitting had no effect on global cognition and there were no significant difference between patients who had quit smoking more than 10 years ago and those who had quit less than 10 years ago, F(1, 63) = 1.72, p = .195.

CONCLUSION

Smoking history was associated to global cognitive impairment in PD even in patients who had quit smoking. These results are in line with findings in healthy older adults that have linked smoking to cognitive impairment, global brain atrophy and functional changes. Future studies should consider a broader assessment of cognitive functions.

Vascular Risk Factors and Cognition in Parkinson's Disease

Vascular risk factors have been associated with cognitive deficits and incident dementia in the general population, but their role on cognitive dysfunction in Parkinson's disease (PD) is still unclear. The present study addresses the single and cumulative effect of vascular risk factors on cognition in PD patients, taking clinical confounders into account. Standardized neuropsychological assessment was performed in 238 consecutive PD patients. We evaluated the association of single and cumulative vascular risk factors (smoking, diabetes, hypercholesterolemia, hypertension, and heart disease), with the diagnosis of PD normal cognition (PDNC, n = 94), mild cognitive impairment (PD-MCI, n = 111), and dementia (PDD, n = 33). The association between single neuropsychological tests and vascular risk factors was evaluated with covariance analyses adjusted for age at onset, educational levels, gender, disease duration, and motor performance. Age, educational levels, disease duration, and motor function were significantly different between PDNC, PD-MCI, and PDD. Heart disease was the only vascular factor significantly more prevalent in PDD compared with PDNC in adjusted analyses. Performance of tests assessing executive and attention functions were significantly worse in patients with hypertension, heart disease, and/or diabetes (p <  0.05). Heart disease is associated with dementia in PD, suggesting a potential window of intervention. Vascular risk factors act especially on attention and executive functions in PD. Vascular risk stratification may be useful in order to identify PD patients with a greater risk of developing dementia. These findings need to be verified in longitudinal studies.

Meta-analysis of risk factors for Parkinson's disease dementia

Background

Parkinson’s disease (PD) is a common heterogeneous neurodegenerative disorder in elder population. Parkinson’s disease dementia (PDD) is one of the most common non-motor manifestations in PD patients. No comprehensive review has been conducted to assess risk factors for PDD.

Methods

A systemic search for studies on PDD risk factors was performed. Cohort and case–control studies that clearly defined PDD and presented relevant data were included. The data were analyzed to generate a pooled effect size and 95 % confidence interval (CI). Publication bias was assessed using the Egger’s test and the Begg’s test.

Results

A systematic search was conducted and yielded 5195 articles. After screening, 25 studies were included in the current analysis. Development of PDD was positively associated with age (odds ratio [OR] 1.07, 95 % CI 1.03-1.13), male (OR 1.33, 95 % CI 1.08-1.64), higher Unified Parkinson’s Disease Rating Scale (UPDRS) part III scores (relative risk [RR] 1.04, 95 % CI 1.01-1.07), hallucination (OR 2.47, 95 % CI 1.36-4.47), REM sleep behavior disorder (RBD) (OR 8.38, 95 % CI 3.87-18.08), smoking (ever vs. never) (RR 1.93, 95 % CI 1.15-3.26) and hypertension (OR 1.57, 95 % CI 1.11-2.22). An inverse association was found between education (RR 0.94, 95 % CI 0.91-0.98) and PDD. Other reported factors, including age of onset, disease duration of PD, Hoehn and Yahr stage and diabetes mellitus were not significantly associated with PDD.

Conclusions

Advanced age, male, higher UPDRS III scores, hallucination, RBD, smoking and hypertension increase the risk of PDD, whereas higher education is a protective factor for PDD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40035-016-0058-0) contains supplementary material, which is available to authorized users.

The impact of MRI white matter hyperintensities on dementia in Parkinson's disease in relation to the homocysteine level and other vascular risk factors

BACKGROUND

The role of white matter hyperintensities (WMH) and homocysteine (Hcy) and other vascular risk factors in the pathogenesis of Parkinson's disease (PD) dementia (PDD) remains unclear.

OBJECTIVE

The aim of the study was to assess the impact of WMH, Hcy and other biochemical and vascular risk factors on PDD.

METHODS

A total of 192 patients with PD and 184 age- and sex-matched healthy controls were included. A semistructured interview was used to assess demographic and clinical variables with respect to vascular risk factors (arterial hypertension, diabetes mellitus, atrial fibrillation, ischemic heart disease, obliterative atherosclerosis, hypercholesterolemia, smoking, alcohol intake). Unified Parkinson's Disease Rating Scale score, Hoehn-Yahr staging and the Schwab-England activities of daily living scale were used to assess motor abilities and activities of daily living. A complex neuropsychological examination with a battery of tests was used to classify patients into a group with dementia (PDD) and a group without dementia (PD). Neuroradiological examination of MRI scans included visual rating scales for WMH (according to the Wahlund and Erkinjunntti rating scales) and the Scheltens scale for hippocampal atrophy. Blood samples for Hcy, folate, vitamin B12, fibrinogen, lipids, glucose, creatinine, transaminases and thyroid stimulating hormone (TSH) were examined.

RESULTS

Among all patients, 57 (29.7%) fulfilled the diagnostic criteria for dementia. Significantly higher Hcy plasma levels were noted in PD and PDD groups compared to controls (p < 0.05) and in PDD when compared to PD (p < 0.05). According to multivariate regression analysis, WMH (Erkinjuntti scale), high Hcy, low vitamin B12 and folate plasma levels were independent risk factors for PDD. Vascular risk factors did not play any role in the pathogenesis of PDD and WMH.

CONCLUSIONS

WMH along with Hcy, folate and vitamin B12 may impact cognition in PD. Therapy with vitamin B12, folate and catechol-O-methyltransferase inhibitors may play a potential protective role against PDD.

The epidemiology of dementia associated with Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative illness after Alzheimer's disease (AD). Cognitive impairment and dementia are common features in PD and characterized by a wide range of cognitive deficits distinct from those seen in AD. Mild cognitive impairment occurs even early in PD and is associated with shorter time to dementia. The purpose of this review is to present recent findings on clinical aspects of dementia in PD and to elucidate underlying clinical and neurobiological risk factors.

Influence of white matter hyperintensities on the cognition of patients with Parkinson disease

BACKGROUND

White matter hyperintensities (WMH) have been associated with cognitive impairment in elderly persons and in patients with Alzheimer disease. However, the role of WMH in Parkinson disease (PD) dementia remains to be elucidated.

METHODS

The cohort for this study comprised 71 consecutive patients with PD, all of whom completed a clinical assessment, neuropsychologic investigation, and magnetic resonance imaging of brain. WMH were rated using the semiquantitative visual rating system proposed by Scheltens et al.

RESULTS

The PD dementia group had significantly more WMH than the PD without dementia group in the evaluated brain regions except for the infratentorial area. The WMH showed a significant correlation with age, Unified Parkinson's Disease Rating Scale, Mini-Mental State Examination, sum of the box of Clinical Dementia Rating, and many of the cognitive domains. The linear regression model showed that the WMH was independently associated with cognitive impairment in patients with PD, regardless of age, sex, duration or severity of PD symptoms, and vascular risk factors.

CONCLUSIONS

These findings confirm that WMH might be associated with cognitive decline in patients with PD, regardless of age, sex, education status, duration or severity of PD symptoms, and vascular risk factors. This result suggests that other nonvascular factors contribute to the progression of dementia in patients with PD.

The epidemiology of dementia associated with Parkinson disease

Several recent studies have shown that dementia is common in Parkinson's disease (PD), and that in some patients, cognitive impairment occurs even at the time of diagnosis. The point prevalence of dementia in PD is close to 30% and the incidence rate is increased 4-6 times as compared to controls. The cumulative prevalence is very high, at least 75% of PD patients who survive for more than 10 years will develop dementia. The mean time from onset of PD to dementia is approximately 10 years. However, there are considerable variations, and some patients develop dementia early in the disease course. Earlier onset of dementia is associated with more structural brain changes. The most established risk factors for early dementia are old age, severity of motor symptoms, in particular postural and gait disturbances, mild cognitive impairment and visual hallucinations. The genetic contributions to dementia are currently not clear and need to be explored in future studies.

Dementia in Parkinson's disease

Parkinson's disease is the second most common neurodegenerative illness diagnosed in the United States. Dementia is recognized as a common component of advanced Parkinson's disease (PD). In patients with early PD, cognitive changes occur and primarily reflect impairment in executive function. It is unknown if the early cognitive changes detected on neuropsychological testing in Parkinson's disease are predictive of the subsequent development of Parkinson's disease with dementia (PDD). Many patients with PD develop dementia characterized by a wide range of cognitive deficits distinct from those seen in Alzheimer's disease (AD). Neuropsychiatric problems frequently accompany PDD. This chapter reviews the epidemiology, clinical characteristics of early and late cognitive changes, pathology, neuroimaging, diagnosis, and treatment of PDD.

Smoking, nicotine and neuropsychiatric disorders

Tobacco smoking is an extremely addictive and harmful form of nicotine (NIC) consumption, but unfortunately also the most prevalent. Although disproportionately high frequencies of smoking and its health consequences among psychiatric patients are widely known, the neurobiological background of this epidemiological association is still obscure. The diverse neuroactive effects of NIC and some other major tobacco smoke constituents in the central nervous system may underlie this association. This present paper summarizes the pharmacology of NIC and its receptors (nAChR) based on a systematic review of the literature. The role of the brain's reward system(s) in NIC addiction and the results of functional and structural neuroimaging studies on smoking-related states and behaviors (i.e. dependence, craving, withdrawal) are also discussed. In addition, the epidemiological, neurobiological, and genetic aspects of smoking in several specific neuropsychiatric disorders are reviewed and the clinical relevance of smoking in these disease states addressed.

Epidemiology of Parkinson's disease

This chapter discusses the epidemiology of Parkinson's disease (PD). Classically, PD refers to progressive parkinsonism caused by loss of pigmented aminergic brainstem neurons without an identifiable cause, while parkinsonism refers simply to the syndrome of bradykinesia, resting tremor, rigidity and postural reflex impairment. Over nearly two centuries, Parkinson's clinical description has provided the framework for clinical investigations, including epidemiologic ones. Descriptions of PD were limited to selected clinical settings until the middle of the 20th century. Since then, epidemiologic approaches have been used not only to investigate the population distribution of PD, but also as a way to glean clues as to the cause of this “idiopathic” disorder. Because PD is relatively infrequent, a large base population must be surveyed to identify sufficient numbers of cases for a study. In some instances, PD cases can be identified through health service rosters within defined geographic areas or in enumerated populations. In others, cases of PD are sought independently of the health care system, such as through door-to-door surveys. While the latter approach is theoretically least likely to exclude cases, the time and cost involved are also greatest using this approach.

Smoking and cognitive function in Parkinson's disease

The risk of dementia among Parkinson's disease (PD) patients is greatly elevated compared to controls, yet little is known about determinants of cognitive function among PD patients. We assessed the relation between cigarette smoking prior to disease onset and later cognitive function among PD patients (n = 286) and age- and sex-matched controls (n = 1144) participating in the Nurses' Health Study and Health Professionals Follow-up Study. Both groups completed telephone-administered assessments of cognitive function. We used linear regression to calculate mean differences in cognitive test scores across smoking categories, adjusted for age, education, sex, age at onset of PD, and years since diagnosis. PD patients scored significantly worse on all tests than their matched controls. In analyses only among PD cases, but not among controls, current smokers at PD onset scored worse than never smokers on the Telephone Interview for Cognitive Status (difference = -0.82, 95% CI: -1.33, -0.30, P = 0.002) as well as on a global score combining results of all tests (difference = -0.36, 95% CI: -0.72, 0.01, P = 0.06). This difference was equivalent to the difference in global score observed among controls approximately 10 years apart in age. Analyses of pack-years of smoking prior to disease onset gave similar results. These findings, nested in prospective cohort studies, suggest that cigarette smoking prior to disease onset is associated with worse cognitive function in PD.

Cognitive, Affective, and Psychiatric Features of Parkinson's Disease

Nonmotor symptoms, including cognitive deterioration and dementia, depression and apathy, and psychosis, are common in Parkinson's disease. Their presence is associated with a tremendous burden for the patient and family members. This article reviews the pathophysiololgy, risks, impact, major features, diagnosis, and treatment of these symptoms in Parkinson's disease.

The influence of cerebrovascular risk factors on incident dementia in patients with Parkinson's disease

OBJECTIVE

To examine if risk factors for cerebrovascular disease would increase the risk for dementia in patients with Parkinson's disease (PD).

METHODS

Non-demented patients were recruited from an epidemiological study of PD in the county of Rogaland, Norway. PD and dementia were diagnosed according to strict diagnostic criteria. Established cerebrovascular risk factors were recorded at baseline, and their influence on incident dementia was assessed 4 years later using logistic regression analysis.

RESULTS

A total of 171 non-demented PD patients constituted the at-risk population. Seventy-two (55%) had at least one cerebrovascular risk factor. A total of 130 subjects (96% of survivors) completed the follow-up examination. Forty-three (33%) new cases of dementia were found. Twenty-five of the 72 (35%) patients with and 18 of the 58 (31%) subjects without any risk factor developed dementia (ns). A significant association with dementia was found for a diagnosis of heart failure in the univariate analyses. However, in the logistic regression analysis none of the cerebrovascular risk factors were significantly associated with incident dementia.

CONCLUSIONS

In this large and representative cohort of patients with PD cerebrovascular risk factors were not associated with incident dementia, indicating that the disease-related degenerative brain changes are the main causes of dementia in PD.

Comparison of age of onset and development of motor complications between smokers and non-smokers in Parkinson's disease

BACKGROUND

There is growing evidence from case-control and from cohort studies that smoking is inversely related to the risk of developing Parkinson's disease (PD). However, it is still controversial if PD starts at an older age in ever-smoking patients compared to never-smoking ones.

PATIENTS AND METHODS

The present retrospective study compares in a large series of 512 out-patients, collected over the last 24 years, the age of onset of the complaints, the age at which PD was diagnosed and the start of levodopa treatment between ever- and never-smokers. Also, the occurrence of long-term side-effects of the drug was evaluated. 184 PD patients with a history of smoking were compared with 328 who had never smoked. The subgroups with and without a family history of PD were analysed separately.

RESULTS

In the overall ever-smoking group, as well as in the subgroup without a family history, the onset of the disease and the time of the diagnosis of PD and the time at which levodopa was started occurred at an older age than in the never-smoking group. This difference could not be demonstrated in the patients with a family history, due to the low number of cases and the lack of statistical power. Although the follow-up period was the same in both study groups, motor fluctuations and dyskinesia were more frequent and appeared earlier after levodopa treatment in the non-smoking compared to the ever-smoking PD patients. Only for cognitive impairment there was a non-significant trend in the smoking group.

CONCLUSION

The present study confirms the protective action of smoking on PD and also suggests some modulating effect of smoking on the dopaminergic system.

Cigarette smoking in Parkinson's disease: Influence on disease progression

Previous studies have shown an inverse association between smoking and the prevalence of Parkinson's disease (PD), suggesting that smoking may induce a biological protection against nigral neuronal damage. In 1993, we examined the frequency of cigarette smokers among 239 patients with PD and two control groups. In addition, the progression of parkinsonism and other clinical features were followed prospectively in smoking and nonsmoking PD patients over an 8-year period. Mortality in the two PD groups was also examined. We found a 50% higher prevalence of smokers in the control groups than in patients with PD. In contrast, during the follow-up period, there were no significant differences in progression of parkinsonism, cognitive impairment, and mood in smoking and nonsmoking patients with PD. Mortality was also similar in the two groups. The lack of influence on disease progression may indicate that cigarette smoking does not have a major neuroprotective effect in patients with already diagnosed PD.

Dementia in Parkinson’s disease

One of the more recently recognized problems in treatment of patients with Parkinson's disease (PD) is development of cognitive dysfunction and, in many cases, frank dementia. As patients with PD live longer, because of improved care and treatment of motor symptoms, dementia in PD is becoming a major contributor to morbidity in the illness. Prevalence studies suggest that up to 30% of patients with PD develop dementia. Dementia in PD patients is often a multifactorial condition. Neuropathologic changes caused by PD itself may cause memory loss. However, some patients with PD and memory decline also have pathologic changes that are more consistent with Alzheimer's disease. Many PD patients have a mix of the two types of pathology. Other factors, such as underlying illnesses, medication side effects, and interaction of therapeutic agents, may contribute to cognitive changes in PD patients. Predictors of development of dementia in PD include advancing age and severity of neurologic symptoms, which may interact with one another to produce this effect. Recent work suggests that tobacco use also may increase risk of PD dementia, despite its possible protective effect against development of PD itself. Presence of psychiatric illness, especially depression, may interfere with cognition and exacerbate memory loss. Reduction in the dose of dopaminergic agents and of other medications may be helpful in partially improving cognitive function in some cases. The balance between improvement of motor function and preservation of cognitive abilities must be weighed, and it is important for clinicians to discuss this trade-off with patients and their families. At this time, there is no US Food and Drug Administration-approved pharmacologic treatment for dementia in PD. However, medication used to treat Alzheimer's disease, such as acetylcholinesterase inhibitors, may slow progression of memory loss in some PD patients. Based on work from small double-blind studies, open-label trials, and case reports, cholinesterase inhibitors may be tried for treatment of dementia in PD, as long as the patient and caregivers understand that these agents are being used on an off-label basis. Surgical intervention, such as deep brain stimulation of the subthalamic nucleus or globus pallidus internus, although useful for treatment of motor symptoms in some PD patients, does not improve cognitive function in most cases and may actually worsen cognition in patients with pre-existing dementia. There is no specific exercise regimen or dietary guidelines for patients with PD who develop dementia. However, patients should be encouraged to lead a healthy lifestyle; this may improve overall well-being, which could impact positively on cognition function. Similarly, although assistive devices have not been developed for people with PD who have memory loss, any aid that increases mobility will probably improve mental and physical function. Clinicians should be mindful of the increased caregiver burden posed by PD patients who also have dementia. They should intervene appropriately to prevent caregiver distress and "burn out." Herbal and nutritional supplements have not been shown in clinical trials to be beneficial for treatment of any type of dementia, and thus are not recommended for PD patients with cognitive decline.

Progress in clinical neurosciences: Parkinson's disease with dementia and dementia with Lewy bodies

Dementia occurs in up to 30% of people with Parkinson's disease and is a major cause of disability. Pathologically, Parkinson's dementia, where dementia follows the onset of parkinsonism by at least one year, overlaps with dementia with Lewy bodies. We review the functional impact, definitions, neuropsychology, epidemiology and pathophysiology of Parkinson's dementia, dementia with Lewy bodies and their overlap. Associated psychiatric and imaging findings are also considered. Lastly, current and emerging approaches to assessment and treatment in patients with these Lewy body associated dementias are presented.

Insulin and neurodegenerative disease: shared and specific mechanisms

Insulin has functions in the brain and dysregulation of these functions may contribute to the expression of late-life neurodegenerative disease. We provide a brief summary of research on the influence of insulin on normal brain function. We then review evidence that perturbation of this role may contribute to the symptoms and pathogenesis of various neurodegenerative disorders, such as Alzheimer's disease, vascular dementia, Parkinson's disease, and Huntington's disease. We conclude by considering whether insulin dysregulation contributes to neurodegenerative disorders through disease-specific or general mechanisms.

What causes mental dysfunction in Parkinson's disease?

Parkinson's disease (PD) is frequently associated with mental dysfunction. Domain-specific cognitive deficits are ubiquitous, and although they may not be clinically apparent in all patients, they are demonstrable by neuropsychological testing. Dementia is less frequent but is present significantly more in PD patients than in controls, with a cumulative prevalence rate up to 40% and up to six-fold increased incidence. Cognitive impairment mainly involves executive and visuospatial functions; memory is secondarily impaired with relatively preserved recognition. Qualitatively, the neuropsychological profile of dementia encompasses the same type of deficits found in nondemented PD patients. The dementia seen in PD, therefore, can be described as a dysexecutive syndrome combined with visuospatial dysfunction and behavioural symptoms. Dopaminergic, noradrenergic, serotoninergic, and cholinergic deficits have all been described as the underlying neurochemical impairment, but the strongest evidence exists for a cholinergic dysfunction. Involvement of brainstem nuclei, limbic structures, and cerebral cortex have been suggested as the site, and Lewy body (LB) degeneration and Alzheimer-type changes as the type of pathology underlying the mental dysfunction in PD. Although there is still some controversy as to the site and type of pathology, recent evidence suggests that LB-type degeneration in limbic structures and cerebral cortex, with consequent synaptic and cell loss, is the main pathological state associated with dementia in PD.

Dementia associated with Parkinson's disease

Dementia affects about 40% of patients with Parkinson's disease; the incidence of dementia in these patients is up to six times that in healthy people. Clinically, the prototype of dementia in PD is a dysexecutive syndrome. Loss of cholinergic, dopaminergic, and noradrenergic innervation has been suggested to be the underlying neurochemical deficits. Nigral pathology alone is probably not sufficient for the development of dementia. Although there is some controversy with regard to the site and type of pathology involved, dementia is likely to be associated with the spread of pathology to other subcortical nuclei, the limbic system, and the cerebral cortex. On the basis of more recent studies, the main pathology seems to be Lewy-body-type degeneration with associated cellular and synaptic loss in cortical and limbic structures. Alzheimer's disease-type pathology is commonly associated with dementia but less predictive. Recent evidence from small studies suggests that cholinesterase inhibitors may be effective in the treatment of dementia associated with PD.