Essential tremor might be less frequent than Parkinson's disease in North Israel Arab villages

Epidemiologic Disparities and Challenges in Non-parkinsonian Tremor Disorders Research: A Scoping Review Emphasizing the Indian Context

Non-parkinsonian tremors represent a heterogeneous spectrum of movement disorders where knowledge gaps persist regarding epidemiology, pathophysiology, and clinical burden. This scoping review aimed to systematically consolidate literature on these disorders in India across the domains of prevalence, biological mechanisms, psychiatric comorbidity, disability impact, and quality of life. A systematic search was undertaken across databases to identify studies on non-parkinsonian tremors in India. Extracted data were synthesized descriptively under themes spanning reported prevalence estimates and variability, proposed biological processes, psychiatric symptom rates, stigma perceptions, and quality-of-life deficits. Methodological appraisal was undertaken. Twenty-nine studies reported prevalence estimates displaying wide variability from 0.09% to 22% for essential tremor, partly attributable to definitional inconsistencies. Proposed pathologic processes centered on cerebellar dysfunction, neurotransmitter disturbances, and genetic risks. Nine studies revealed variable anxiety (6.8%-90%) and depression (3.4%-60%) rates among essential tremor patients, while two indicated perceived stigma. Five studies unanimously concurred significant quality of life impairment in essential tremors. Evidence of dystonic tremor, functional tremor, and other tremors was limited. This review exposed critical knowledge gaps and methodological limitations, while systematically evaluating the Indian literature on non-parkinsonian tremors concerning epidemiology, mechanisms, and clinical burden. Large-scale collaborative research applying standardized diagnostic criteria is imperative to determine contemporary prevalence statistics and comprehensively characterize the multifaceted disability footprint to inform patient-centric models optimizing diagnosis and holistic care.

Essential tremor

Essential tremor (ET) is one of the most common movement disorders, with a reported >60 million affected individuals worldwide. The definition and underlying pathophysiology of ET are contentious. Patients present primarily with motor features such as postural and action tremors, but may also have other non-motor features, including cognitive impairment and neuropsychiatric symptoms. Genetics account for most of the ET risk but environmental factors may also be involved. However, the variable penetrance and challenges in validating data make gene-environment analysis difficult. Structural changes in cerebellar Purkinje cells and neighbouring neuronal populations have been observed in post-mortem studies, and other studies have found GABAergic dysfunction and dysregulation of the cerebellar-thalamic-cortical circuitry. Commonly prescribed medications include propranolol and primidone. Deep brain stimulation and ultrasound thalamotomy are surgical options in patients with medically intractable ET. Further research in post-mortem studies, and animal and cell-based models may help identify new pathophysiological clues and therapeutic targets and, together with advances in omics and machine learning, may facilitate the development of precision medicine for patients with ET.

How Common is Essential Tremor? Update on the Worldwide Prevalence of Essential Tremor

Background

Essential tremor (ET) is among the most prevalent movement disorders. Comprehensive reviews of disease prevalence were published in 1998 and 2010 but not since then. We reviewed the prevalence of ET in population-based epidemiological studies, derived a precise summary estimate of prevalence from these studies, and examined differences in prevalence across studies. We used two methods: a descriptive-analytical approach and a meta-analysis.

Methods

A PUBMED search yielded 14 published papers since the 2010 review.

Results

There were 42 population-based prevalence studies (23 countries and 6 continents). In a meta-analysis, pooled prevalence (all ages) = 1.33%, with statistically significant heterogeneity across studies (I2 = 99.3%, p < 0.0001). In additional descriptive analyses, median crude prevalence (all ages) = 0.4% and mean = 0.67%. Prevalence increased markedly with age, and especially with advanced age. In the meta-analysis, prevalence (age ≥ 65 years) = 5.79%, and in descriptive analyses, median crude prevalence (age ≥ 60-65) = 5.9% and mean = 8.0%. In the oldest age groups, median prevalence = 9.3%, with several studies reporting values >20%. The prevalence increased by 74% for every decade increase in age (p < 0.0001). Gender did not impact the prevalence of ET (p = 0.90).

Discussion

Precise prevalence estimates are important because they form the numerical basis for public health initiatives and offer clues about underlying biological factors of mechanistic importance. The prevalence of ET among those age ≥ 65 is similar to that reported for Alzheimer's disease in elders, suggesting that ET may be the most common neurodegenerative disease.

Sex differences in movement disorders

In a range of neurological conditions, including movement disorders, sex-related differences are emerging not only in brain anatomy and function, but also in pathogenesis, clinical features and response to treatment. In Parkinson disease (PD), for example, oestrogens can influence the severity of motor symptoms, whereas elevation of androgens can exacerbate tic disorders. Nevertheless, the real impact of sex differences in movement disorders remains under-recognized. In this article, we provide an up-to-date review of sex-related differences in PD and the most common hyperkinetic movement disorders, namely, essential tremor, dystonia, Huntington disease and other chorea syndromes, and Tourette syndrome and other chronic tic disorders. We highlight the most relevant clinical aspects of movement disorders that differ between men and women. Increased recognition of these differences and their impact on patient care could aid the development of tailored approaches to the management of movement disorders and enable the optimization of preclinical research and clinical studies.

Movement Disorders and Deep Brain Stimulation in the Middle East

BACKGROUND

Deep brain stimulation (DBS) is a well-established neuromodulation therapy for advanced Parkinson disease, essential tremor and dystonia. In as much as this therapy is being developed in the Middle East, a better understanding of the incidence and prevalence of movement disorders, health care, and social framework is required for the region.

METHODS

We reviewed current literature on the incidence and prevalence of various movement disorders in the Middle East amenable to DBS surgery. We also assessed recent efforts to develop DBS in the region.

RESULTS

Available data on incidence and prevalence of movement disorders in the Middle East are old, inconclusive, and conflicting. We identify key areas such as cultural background, availability of accessible information, training, infrastructure, and public support groups in the region that may pose challenges.

CONCLUSIONS

The Middle East is projected to be a growing market for neuromodulation. The available data on incidence and prevalence of movement disorders is from studies that were small, partial, and old, with inconsistent results, highlighting the need for newer, better-designed, and larger studies. DBS in the Middle East will need assessment of incidence and prevalence of movement disorders, existing challenges to its application, and focused efforts on key opportunities to foster development of DBS for this underserved region. This article is an attempt to identify and explore these challenges and propose solutions in anticipation.

Variable PARK2 Mutations Cause Early-Onset Parkinson's Disease in a Small Restricted Population

Early-onset Parkinson's disease (EOPD) is less common than the typical adult-onset PD and may be associated with a genetic etiology. Mutations in several genes are known to cause autosomal recessive (AR) PD. This study aimed to detect the etiology of EOPD in consanguineous families or families living in a specific small geographic region in Israel. Six families with EOPD affecting more than a single individual were recruited. Homozygous mapping analysis using a single-nucleotide polymorphism-based array was performed in all families, followed by Sanger sequencing of related genes based on the mapping results. In addition, all families underwent PARK2 sequencing and testing for large deletions and duplications in PD-associated genes. Different truncating mutations were detected in the PARK2 gene among affected individuals of three families: c.996C>A (p.Cys332X) and c.101delA in either homozygous or compound heterozygous fashion. Exon 4 deletion was detected in a heterozygous manner in a late-onset PD and in homozygous state in early-onset disease in the same family. No disease-causing mutations were detected in any other tested genes. In total, mutations in the PARK2 gene were detected in four of the six tested families with a history of EOPD. These results further demonstrate the role of PARK2 in AR PD. We recommend genetic analysis for the PARK2 gene when AR PD is suspected.

Estimating the risk for conversion from mild cognitive impairment to Alzheimer's disease in an elderly Arab community

BACKGROUND

Vascular risk factors and lack of formal education may increase the risk of Alzheimer's disease (AD).

OBJECTIVE

To determine the contribution of vascular risk factors and education to the risk of mild cognitive impairment (MCI) and AD and to estimate the risk for conversion from MCI to AD.

METHODS

This door-to-door survey was performed by an Arab-speaking team in Wadi Ara villages in Israel. All consenting residents aged ≥ 65 years were interviewed for medical history and underwent neurological and cognitive examinations. Individuals were cognitively classified as normal (CN), MCI, AD, vascular dementia, or unclassifiable. MCI patients were re-examined at least one year later to determine conversion to AD. The contributions of age, gender, school years, and vascular risk factors to the probability of conversion were estimated using logistic regression models.

RESULTS

Of the 906 participants, 297 (33%) had MCI and 95 (10%) had AD. Older age (p = 0.0008), female gender (p = 0.023), low schooling (p < 0.0001), and hypertension (p = 0.0002) significantly accounted for risk of MCI versus CN, and diabetes was borderline (p = 0.051). The risk of AD versus CN was significantly associated with age (p < 0.0001), female gender (p < 0.0001), low schooling (p = 0.004) and hypertension (p = 0.049). Of the 231 subjects with MCI that were re-examined, 65 converted to AD.

CONCLUSIONS

In this population, age, female gender, lack of formal education, and hypertension are risk factors for both AD and MCI. Conversion risk from MCI to AD could be estimated as a function of age, time interval between examinations, and hypertension.

Tremor in the elderly: Essential and aging-related tremor

BACKGROUND

Isolated tremor in the elderly is commonly diagnosed as essential tremor (ET). The prevalence of tremor increases steeply with increasing age, whereas hereditary tremor is becoming less common. Moreover, late-manifesting tremor seems to be associated with dementia and earlier mortality. We hypothesize that different entities underlie tremor in the elderly.

METHODS

Two thousand four hundred forty-eight subjects from the Longitudinal Study of Aging Danish Twins older than 70 y answered screening questions for ET in 2001. Two thousand fifty-six (84%) participants drew Archimedes spirals to measure their tremor severity, and classical aging phenotypes were assessed. A subgroup of 276 individuals fulfilling either screening criteria for ET or being controls were personally assessed. Medications and mortality data are available.

RESULTS

The spiral score increased with age. The spiral score correlated with tremor severity. For the whole cohort, mortality was significantly correlated with the spiral score, and higher spiral scores were associated with lower physical and cognitive functioning. Multivariate analysis identified higher spiral scores as an independent risk factor for mortality. In contrast, the ET patients did not show an increased but rather a lower mortality rate although it was not statistically significant. Consistent with a slower than normal aging, they were also physically and cognitively better functioning than controls.

CONCLUSIONS

Because incident tremors beyond 70 y of age show worse aging parameters and mortality than controls and ET, we propose to label it 'aging-related tremor' (ART). This tremor starts later in life and is accompanied by subtle signs of aging both cognitively and physically. More detailed clinical features and pathogenesis warrant further assessment.

The prevalence of essential tremor in elderly Koreans

Essential tremor (ET) is one of the most common movement disorders. The prevalence of ET varies substantially among studies. In Korea, there is no well-designed epidemiological study of the prevalence of ET. Thus, we investigated the prevalence of ET in a community in Korea. Standardized interviews and in-person neurological examinations were performed in a random sample of the elderly aged 65 yr or older. Next, movement specialists attempted to diagnose ET clinically. People who showed equivocal parkinsonian features underwent dopamine transporter imaging using [(123)I]-FP-CIT SPECT, to differentiate ET from parkinsonism. A total of 714 subjects participated in this population-based study. Twenty six of these subjects were diagnosed as having ET. The crude prevalence of ET was 3.64 per 100 persons. Age, gender, or education period were not different between the ET patients and the non-ET subjects. The prevalence of ET was slightly lower than those reported in previous studies. Further studies including more subjects are warranted.

How many people in the USA have essential tremor? Deriving a population estimate based on epidemiological data

BACKGROUND

Essential tremor (ET) is often reported to be among the most prevalent movement disorders, yet the precise number of cases in the USA is not known. The goal of the current analyses was to use published data from epidemiological studies to derive an estimate of the number of people currently residing in the USA who have ET.

METHODS

A PubMed search was conducted to identify population-based prevalence studies of ET. The methodology of 34 identified studies was assessed. Then the three most methodologically rigorous studies were selected, and age-specific prevalence data were abstracted. US census data from 2012 were used to determine the population in the USA by 10-year age categories.

RESULTS

Using data from three studies, estimates of the number of ET cases (2012) ranged from 6.38 to 7.63 million (mean = 7.01 million). This corresponds to approximately 2.2% of the US population.

DISCUSSION

Knowing the number of ET cases in the USA is important in terms of estimating the medical burden on communities and society, and providing an objective metric on which to base health resource planning.

Prayer at midlife is associated with reduced risk of cognitive decline in Arabic women

Midlife habits may be important for the later development of Alzheimer's disease (AD). We estimated the contribution of midlife prayer to the development of cognitive decline. In a door-to-door survey, residents aged ≥65 years were systematically evaluated in Arabic including medical history, neurological, cognitive examination, and a midlife leisure-activities questionnaire. Praying was assessed by the number of monthly praying hours at midlife. Stepwise logistic regression models were used to evaluate the effect of prayer on the odds of mild cognitive impairment (MCI) and AD versus cognitively normal individuals. Of 935 individuals that were approached, 778 [normal controls (n=448), AD (n=92) and MCI (n=238)] were evaluated. A higher proportion of cognitively normal individuals engaged in prayer at midlife [(87%) versus MCI (71%) or AD (69%) (p<0.0001)]. Since 94% of males engaged in prayer, the effect on cognitive decline could not be assessed in men. Among women, stepwise logistic regression adjusted for age and education, showed that prayer was significantly associated with reduced risk of MCI (p=0.027, OR=0.55, 95% CI 0.33-0.94), but not AD. Among individuals endorsing prayer activity, the amount of prayer was not associated with MCI or AD in either gender. Praying at midlife is associated with lower risk of mild cognitive impairment in women.

High prevalence of mild cognitive impairment and Alzheimer's disease in arabic villages in northern Israel: impact of gender and education

The prevalence of mild cognitive impairment (MCI) and Alzheimer's disease (AD) have not been well been studied in Arab populations. In a door-to-door study of all residents aged ≥ 65 years in Wadi-Ara, an Arab community in northern Israel, we estimated the prevalence of AD, MCI, and the risk of conversion to AD. Subjects were classified as cognitively normal, MCI, AD, or other based on neurological and cognitive examination (in Arabic). MCI subjects were re-examined (interval ≥ 1 year) to determine conversion to AD and contributions of age, gender, and education to the probability of conversion. Of the 944 participants (96.6% of those approached; 49.4% men), 92 (9.8%) had AD. An unusually high prevalence of MCI (n = 303, 32.1%) was observed. Since the majority of women (77.2%) had no schooling, we estimated the effect of gender on the risk of AD and MCI among subjects without schooling and of school years among men. Among subjects with no schooling (n = 452), age (p = 0.02) and female gender (p < 0.0001) were significant predictors of AD, whereas risk of MCI increased only with age (p = 0.0001). Among men (n = 318), age increased the risk (p < 0.0001), school years reduced the risk of AD (p = 0.039) and similarly for MCI [age (p = 0.0001); school years (p = 0.0007)]. Age (p = 0.013), but not gender or school years, was a significant predictor of conversion from MCI to AD (annual rate 5.7%). The prevalence of MCI and AD are unusually high in Wadi Ara, while the rate of conversion from MCI to AD is low. Yet unidentified genetic factors might underlie this observation.

Mild cognitive impairment is associated with mild parkinsonian signs in a door-to-door study

Mild cognitive impairment (MCI) and healthy aging have been shown to be associated with mild parkinsonian signs (MPS). We performed a door-to-door observational and follow-up study amongst consenting residents of Wadi Ara Arab villages in northern Israel aged ≥65 years (n=687) to examine whether MPS represent a risk factor for MCI and/or conversion from MCI to Alzheimer's disease (AD). In Phase 1, 223 cognitively normal (CN) and 173 MCI subjects were assessed by interview for medical history, neurological examination, motor part of the Unified Parkinson Disease Rating Scale (mUPDRS) (divided into item-clusters: axial, limb bradykinesia, tremor and rigidity) and cognitive tests. MCI subjects (n=111) were re-evaluated in Phase 2 for conversion to AD at least one year after initial assessment. MCI subjects had a higher frequency of axial dysfunction (8.7% vs. 1.3%) and limb bradykinesia (10.4% vs. 1.3%) than CN subjects (p<0.001, both). Stepwise logistic regression analysis estimating the probability of MCI vs. CN revealed higher mUPDRS (OR =1.19, 95% CI, 1.05 to 1.35, p=0.006) and higher limb bradykinesia scores (OR=1.75, 95% CI, 1.2 to 2.56, p=0.003) and not age as explanatory variables. Presence of MPS did not predict conversion to AD after adjustment for age and time-interval. These results suggest that axial and bradykinetic parkinsonian signs represent risk factors for MCI but MPS may not predict conversion from MCI to AD.

Phenotype of the 202 adenine deletion in the parkin gene: 40 years of follow-up

BACKGROUND

We describe the four decades follow-up of 14 parkin patients belonging to two large eight-generation-long in-bred Muslim-Arab kindreds.

RESULTS

All patients had a single base-pair of adenine deletion at nucleotide 202 of exon 2 (202A) of the parkin gene (all homozygous, one heterozygous). Parkinson's disease onset age was 17-68 years. Special features were intractable axial symptoms (low back pain, scoliosis, camptocormia, antecollis), postural tremor, and preserved cognition.

CONCLUSIONS

The 202A deletion of the parkin gene causes early-onset Parkinson's disease with marked levodopa/STN-DBS-resistant axial features. Postural tremor and preserved cognition, even after 40 years of disease, were also evident.

Hypertension increases the probability of Alzheimer's disease and of mild cognitive impairment in an Arab community in northern Israel

BACKGROUND

We aimed to determine whether vascular risk factors are associated with Alzheimer's disease (AD) and mild cognitive impairment (MCI) in an elderly Arab population.

METHODS

An Arabic-speaking team performed a door-to-door survey of consecutive residents aged > or =65 years. We estimated the odds of AD or MCI versus normal controls as a function of age, gender, education and presence of vascular factors by multinomial logistic regression with interactions.

RESULTS

Out of 767 subjects (54% men), 444 were cognitively normal, 234 had MCI and 89 had AD. AD was significantly associated with hypertension (p = 0.01; OR = 2.08; 95% CI: 1.18-3.65), age (p < 0.0001; OR = 1.19; 95% CI: 1.14-1.24), female gender (p = 0.0016; OR = 3.06; 95% CI: 1.53-6.15) and education (p = 0.0002; OR = 0.75; 95% CI: 0.65-0.88). MCI was significantly associated with hypertension (p = 0.0042; OR = 1.69; 95% CI: 1.25-2.44), age (p < 0.0001; OR = 1.06; 95% CI: 1.03-1.09) and education (p < 0.0001; OR = 0.76; 95% CI: 0.71-0.83), but not with gender.

CONCLUSIONS

Hypertension, older age and low education significantly increase the probability of AD and MCI. The effect of hypertension on the odds of AD versus controls is over and above the effects of age, gender and education. For MCI versus controls there is no gender effect, and the effect of hypertension is over and above the effects of age and education.

Epidemiology and management of essential tremor in children

Essential tremor (ET) is a common, often familial, movement disorder characterized by tremor of the limbs, head, and voice. Epidemiological surveys indicate that up to 5% of the adult population has ET, and 5-30% of adults with ET report symptom onset during childhood. There is, however, little published regarding ET in the pediatric population, and no prospective studies targeted specifically to children. Retrospective studies from subspecialty movement disorder clinics indicate that childhood-onset ET is usually hereditary, begins at a mean age of 6 years, and affects boys three times as often as girls. While ET occasionally results in disability during childhood, only one-quarter of children seeing a neurologist for ET require pharmacotherapy. Small case series suggest that propranolol is effective in approximately 50% of children with ET, but controlled treatment trials are lacking.