Prevalence of essential tremor in the city of Kolkata, India: a house-to-house survey

Background and purpose:  Prevalence of essential tremor (ET), one of the most common movement disorders, has not been properly evaluated amongst heterogeneous population in India.
Methods:  We conducted a cross-sectional epidemiological study on the prevalence of ET in a randomly stratified population in the metropolitan city of Kolkata (erstwhile Calcutta), India, by a field team headed by a specialist doctor. A two-stage house-to-house survey was carried out with a validated screening instrument.
Results:  A population of 52377 was screened and a total of 184 cases of ET were identified as per pre-defined criteria and the prevalence rate adjusted to World Standard Population was 3.95 per 1000 (95% CI: 3.40–4.56). Age-specific prevalence showed increasing prevalence with aging. Sex-specific prevalence did not show significant difference between men and women. Socio-economic factors appeared to influence the prevalence and risk of ET was higher amongst slum dwellers versus non-slum population (odd ratio-2.29). Family history was positive in about one-fifth of the cases.
Conclusion:  This study has documented that the prevalence of ET above 40 years in India is similar to that of many countries globally and common amongst slum dwellers and there are fewer familial cases.     

Jaw tremor: prevalence and clinical correlates in three essential tremor case samples.

The spectrum of involuntary movements seen in essential tremor (ET) is limited. Jaw tremor is one such movement. The prevalence and clinical correlates of jaw tremor have not been studied in detail. The objective of this study was to estimate the prevalence and examine the clinical correlates of jaw tremor in ET using ET cases from three distinct settings (population, tertiary-referral center, brain repository). All ET cases underwent a videotaped tremor examination in which tremors (including limb, head, voice, and jaw) were assessed. The prevalence [95% confidence interval (CI)] of jaw tremor was lowest in the population sample (7.5%; 3.9%-14.2%), intermediate in the tertiary-referral center (10.1%; 6.8%-14.7%), and highest in the brain repository (18.0%; 12.3%-25.5%; P = 0.03). Jaw tremor was associated with older age (P < 0.001), more severe action tremor of the arms (P < 0.001), and presence of head and voice tremor (P < 0.001). Jaw tremor was present in 4/14 (28.6%) ET cases with consistent rest tremor vs. 15/193 (7.8%) cases without rest tremor (odds ratio = 4.8; 95% CI = 1.3-7.0; P = 0.009). The prevalence of jaw tremor was 7.5% to 18.0% and was dependent on the mode of ascertainment, being least prevalent in a population-based sample. ET cases with jaw tremor had a more clinically severe and more topographically widespread disorder. The association in our study between jaw tremor and rest tremor, along with the published observation that jaw tremor can occur in Parkinson's disease (PD), raises the question whether jaw tremor in ET is a marker for subsequent conversion to PD.     

Essential tremor in a Finnish population

A two-phase epidemiological study of essential tremor was carried out by investigating a rural population aged over 40 years in 2 municipalities in southwestern Finland. In the first phase, the subjects answered a questionnaire as to whether they had experienced tremor during the month preceding the inquiry. In the second phase, the persons who had tremor often or fairly often, were examined clinically. The total prevalence of essential tremor, calculated on the basis of clinically established cases, was 55.5‰ of the population aged over 40 years. The disease became more prevalent with advancing age and was, with the exception of the oldest age-group, more common in men than in women.     

Essential tremor prevalence is low in Arabic villages in Israel

Objective To estimate the prevalence of essential tremor (ET) in Arabic villages of Wadi Ara. Background The prevalence ET which is higher than Parkinson’s disease in North America and Europe, differs according to study population and methodology. Since hospital record based epidemiology carries referral bias and might provide low estimates of ET prevalence, we carried a population based survey. Methods This door-to-door survey comprised the Arabic villages of Wadi Ara in Northern Israel. Consecutive residents who agreed to participate in the study and were older than 64 years at prevalence day, underwent neurological examination. Medical and family history, medication and response to medication were recorded. Results Of the 444 subjects that were approached, 428 agreed to participate in the study (refusal rate 3.6%). Four were excluded owing to severe systemic disease. The study population consisted of 424 subjects (54% men, mean age 74 ± 7 years). A clearly oscillatory action tremor of moderate amplitude was observed in 8 patients (age 75 ± 7 years). Six patients had another possible cause of tremor. The prevalence of ET was calculated as 1.89% (95% CI 1.76–2.0) when all tremor cases were accepted as possible ET and 0.47% (95 CI 0.43–0.52) when patients with other causes of tremor were excluded. Conclusions The prevalence of ET in Arabic villages of Wadi Ara is low. Received in revised form: 17 January 2006     

Is essential tremor predominantly a kinetic or a postural tremor? A clinical and electrophysiological study

Both postural and kinetic tremors may occur in essential tremor (ET), however the relative contribution of each is not clear. ET has been variably defined with respect to kinetic and postural tremors. To examine the relative severity of postural and kinetic tremors in ET, 50 ET cases from a clinic and 55 from a community underwent a videotaped tremor examination. Kinetic and postural tremors were rated using a validated clinical rating scale (score range, 0-3). Thirty-one cases also underwent accelerometry to precisely quantify tremor amplitude. In clinic cases, the mean postural tremor rating was 1.25 (S.D., 0.89). The mean kinetic tremor rating was 52% higher (1.90; S.D., 0.57; P < 0.001). The community cases had similar characteristics. Sixty percent of the 105 cases had postural tremor ratings scoring 0 or 1 (no tremor or low amplitude, intermittent tremor). In clinic cases, the mean amplitude of postural tremor during tremor analysis was 0.51 mm (S.D., 0.66 mm), and the mean amplitude of kinetic tremor was 2.91 mm (S.D., 2.11 mm; P < 0.01). Similar values were obtained for community cases. These quantitative data suggest that kinetic tremor is more severe than postural tremor in ET. The majority of cases had mild or absent postural tremor. Despite this, ET is defined only as a postural tremor in many studies. Our data argue for a more consistent inclusion of kinetic tremor in diagnostic criteria for ET.     

Short sleep duration heralds essential tremor: A prospective,population‐based study

Lewy bodies have been described in the locus coeruleus of some patients with essential tremor (ET), and this brainstem nucleus plays an important role in sleep cycle regulation. Despite this, no studies have investigated the relationship between daily sleep duration and the risk of ET. We determined whether baseline daily sleep duration was associated with an increased risk of incident ET. In this prospective, population‐based study of individuals > 65 years of age (the Neurological Disorders in Central Spain [NEDICES] cohort), participants were evaluated at baseline and 3 years later. At baseline, participants indicated their daily sleep duration as the sum of nighttime sleep and daytime napping. The average daily total sleep duration was grouped into four categories: ≤ 5 hours (short sleepers), 6 hours, 7 to 8 hours (reference), and ≥ 9 hours (long sleepers) hours. In total, 3,303 participants had a median duration of follow‐up of 3.3 years. There were 76 incident ET cases at follow‐up. The relative risks for short sleepers and for long sleepers were 2.25 (95% confidence interval [CI], 1.21‐4.16; P = 0.01) and 0.74 (95% CI, 0.41‐1.32; P = 0.31), respectively. After adjustment for potential confounders, including age, sex, educational level, current smoker, current drinker, and depressive symptoms or antidepressant use, the risk remained significantly increased for short sleepers (relative risk, 1.95; 95% CI, 1.03‐3.70; P = 0.04]). The results indicated that short daily sleep duration may be a pre‐motor marker for ET. Additional prospective studies are needed to confirm these results, and the biological basis for this association merits additional investigation. © 2013 International Parkinson and Movement Disorder Society     

Longitudinal study of clinical and neurophysiological features in essential tremor

Background and purpose

Essential tremor (ET) is a common and heterogeneous disorder characterized by postural/kinetic tremor of the upper limbs and other body segments and by non-motor symptoms, including cognitive and psychiatric abnormalities. Only a limited number of longitudinal studies have comprehensively and simultaneously investigated motor and non-motor symptom progression in ET. Possible soft signs that configure the ET-plus diagnosis are also under-investigated in follow-up studies. We aimed to longitudinally investigate the progression of ET manifestations by means of clinical and neurophysiological evaluation.

Methods

Thirty-seven ET patients underwent evaluation at baseline (T0) and at follow-up (T1; mean interval ± SD = 39.89 ± 9.83 months). The assessment included the clinical and kinematic evaluation of tremor and voluntary movement execution, as well as the investigation of cognitive and psychiatric disorders.

Results

A higher percentage of patients showed tremor in multiple body segments and rest tremor at T1 as compared to T0 (all p-values < 0.01). At T1, the kinematic analysis revealed reduced finger-tapping movement amplitude and velocity as compared to T0 (both p-values < 0.001). The prevalence of cognitive and psychiatric disorders did not change between T0 and T1. Female sex, absence of family history, and rest tremor at baseline were identified as predictive factors of worse disease progression.

Conclusions

ET progression is characterized by the spread of tremor in multiple body segments and by the emergence of soft signs. We also identified possible predictors of disease worsening. The results contribute to a better understanding of ET classification and pathophysiology.     

Regional and racial differences in the prevalence of physician-diagnosed essential tremor in the United States.

For reasons that are unclear, prevalence estimates of essential tremor (ET) differ considerably across the United States. Separate communities have never been sampled within the framework of the same study to substantiate these differences. We estimated the prevalence of physician-diagnosed ET in the elderly in four communities in the United States in whom the same screening questions were used, and examined whether this prevalence differed between Caucasians and African Americans. The Cardiovascular Health Study recruited a sample of Medicare beneficiaries >/=65 years of age from four communities in different regions of the United States. In 1998 to 1999, 3,494 participants (mean age, 80.0 years; range, 70-103 years) answered a 12-question screen for ET, including the question, "has a doctor diagnosed you as having familial tremor or benign essential tremor?" Fifty-four participants reported that a doctor had diagnosed them as having ET (1.5%; 95% confidence interval, [CI], 1.1-2.0%). Prevalence was similar across the four communities (1.1-2.0%). A larger proportion of Caucasians than African Americans reported a diagnosis of ET (1.7% vs. 0.4%; odds ratio = 4.9; 95% CI, 1.2-20.2; P = 0.028). In a logistic regression analysis, physician-diagnosed ET was associated with Caucasian ethnicity (P = 0.038) but not with age, gender, education, mental status or depression scores, income, smoking status, or alcohol consumption. When a standardized screening question was used, the proportion of participants with physician-diagnosed ET was similar across four communities, suggesting that the prevalence of this condition may be less variable than is often reported. Caucasians were five times more likely to have physician-diagnosed ET than were African Americans. This study does not provide an explanation for this difference, which deserves further study.     

Clinical characteristics of essential tremor in Taiwan: an exploratory‐comparative study

Background: There are few large‐scale clinical analyses of essential tremor (ET) in Asia. We studied the detailed clinical profile with emphasizing the age of onset, tremor location, specific tremor patterns, and rate of progression (ROP) to delineate the characteristics of Taiwanese ET patients and found the difference between the Taiwanese and the Caucasians ET patients. Methods: All ET patients fulfilled the Movement Disorders Society diagnosis criteria were investigated with a standardized assessment protocol, which including clinical evaluation, uniform severity scoring, self‐reported questionnaires, accelerometry, surface electromyography, and videotaped tremor examination. Results: Of 219 patients recruited from July 2008 to October 2009, 153 completed the study protocol. Their mean age was 58.9 years and 47% were women, and 33.3% had family history (FH). There was bimodal distribution in age of tremor onset in patients without but not in those with FH. Head tremor (HT) was present in 48 of 153 (31%) patients. Patients with HT showed slower tremor frequency and less ROP than those without HT. Sixty‐seven (44%) patients presented with intention tremor (IT). Male gender and voice tremor were predictive factors of IT occurrence. Conclusions: Comparing with the Caucasians, Taiwanese ET patients have different patterns of onset‐age distribution and lack of female predominance in ET with HT. However, patients with IT and without HT also progressed more rapid as found in the Caucasian.     

Effects of unilateral stereotactic posterior striatotomy on harmaline‐induced tremor in rats

Although long known and the most prevalent movement disorder, pathophysiology of essential tremor (ET) remains controversial. The most accepted hypothesis is that it is caused by a dysfunction of the olivocerebellar system. Vilela Filho et al. [2001; Stereotact Funct Neurosurg 77:149–150], however, reported a patient with unilateral hand ET that was completely relieved after a stroke restricted to the contralateral posterior putamen and suggested that ET could be the clinical manifestation of posterior putamen hyperactivity. The present study was designed to evaluate this hypothesis in the most often used model of ET, harmaline‐induced tremor in rats. Fifty‐four male Wistar rats were randomly distributed into three groups: experimental (EG), surgical control (SCG), and pharmacological control (PCG) groups. EG animals underwent stereotactic unilateral posterior striatotomy. SCG rats underwent sham lesion at the same target. PCG served exclusively as controls for harmaline effects. All animals received, postoperatively, intraperitoneal harmaline, and the induced tremor was video‐recorded for later evaluation by a blind observer. Thirteen animals were excluded from the study. Limb tremor was reduced ipsilaterally to the operation in 20 of 21 rats of EG and in two of nine of SCG, being asymmetric in one of 10 of PCG rats. Comparisons between EG × SCG and EG × PCG were statistically significant, but not between SCG × PCG. Limb tremor reduction was greater in anterior than in posterior paws. Lateral lesions yielded better results than medial lesions. These results suggest that the posterior striatum is involved with harmaline‐induced tremor in rats and support the hypothesis presented. © 2013 Wiley Periodicals, Inc.