Epidemiología del temblor esencial / Epidemiology of essential tremor

INTRODUCCIÓN: El temblor esencial es una de las patologías con más peso proporcional en las consultas de neurología. Sin embargo, en comparación con otras enfermedades neurodegenerativas, poco se sabe en cuanto a su prevalencia y, en especial, a su incidencia y mortalidad, así como cuáles son los factores genéticos, ambientales y biológicos de importancia etiológica. OBJETIVOS: Exponer los datos más relevantes sobre la epidemiología descriptiva (prevalencia, incidencia y mortalidad) del temblor esencial y comentar algunos de los principales factores de riesgo o protectores de esta enfermedad (epidemiología analítica) que se han sugerido fundamentalmente gracias a los datos obtenidos de las grandes cohortes poblacionales. DESARROLLO: Análisis de los estudios poblacionales más significativos, en especial los realizados con metodología «puerta a puerta», y de los estudios analíticos más relevantes. CONCLUSIONES: Los datos sobre la epidemiología del temblor esencial son aún limitados. Las estimaciones de la prevalencia de temblor esencial varían mucho a lo largo de los diferentes países, lo que hace difícil establecer su prevalencia con precisión. Aun así, la prevalencia aumenta con la edad, es decir, es una enfermedad ligada al envejecimiento. En los sujetos mayores de 60 años se situaría en el 2,3-14,3% (mediana: 6,3%). No obstante, se requieren más estudios, fundamentalmente de incidencia y de mortalidad. En los últimos años se han hecho avances en el conocimiento de algunos factores ambientales como factores de riesgo, en especial los harmanos

INTRODUCTION: Essential tremor is one of the pathologies with more proportional weight in neurology consultations. However, compared to other neurodegenerative diseases, little is known about its prevalence and, in particular, its incidence and mortality, as well as which are the genetic, environmental, and biological factors of etiological importance. AIMS. To present the most relevant data on the descriptive epidemiology (prevalence, incidence, and mortality) of essential tremor. Likewise, some of the main risk or protective factors of this disease (analytical epidemiology) that have been suggested mainly thanks to the data obtained from large population cohorts will be discussed. DEVELOPMENT: We analysed the most significant population studies, especially those carried out through door-to-door methodology, and the most relevant analytical studies. CONCLUSIONS: Data on the epidemiology of essential tremor are still limited. Estimates of the prevalence of essential tremor vary widely across countries, which makes it difficult to accurately establish its prevalence. Even so, its prevalence increases with age; that is, it is a disease linked to aging. In subjects older than 60 years, essential tremor prevalence would be between 2.3-14.3% (median: 6.3%). However, further studies are needed in this regard, mainly studies of incidence and mortality. In recent years, advances have been made in the knowledge of some environmental factors, such as risk factors, especially the harmanes

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.

Long-term follow-up of thalamic deep brain stimulation for essential tremor - patient satisfaction and mortality.

BACKGROUND: Ventral intermediate thalamic nucleus (VIM) deep brain stimulation (DBS) is an effective treatment for tremor, but there is limited data on long-term efficacy and mortality after VIM-DBS. Here we report the analysis of patient satisfaction and mortality in all patients treated in our center 1996-2010 with VIM-DBS for essential tremor (ET). METHODS: Forty-six consecutive patients were included in this study. Medical records were reviewed, and a follow-up questionnaire was sent to all surviving patients. RESULTS: Seventy percent of all possible participants (26 patients) answered the questionnaire. Follow-up time for the responding patients was median 6.0 years (2-16). Median self-reported score on visual analogue scale of the initial postoperative effect on tremor was 8.5 (0.1-10), with a significant reduction to 7.4 (0-10) at follow-up (p = 0.001). Patients reported a median score of 10 (0-10) for overall patient satisfaction with VIM-DBS treatment. Eight patients (17%) died after median 8.9 years (0.6-15) after surgery, at median age 77.4 years (70-89). One patient (2%) committed suicide seven months after the operation. Calculated standard mortality ratio among ET patients was 1.3 (CI 0.6-2.6), similar to the general population. CONCLUSION: We found no significant increase in mortality in this cohort of VIM-DBS operated ET patients compared to the general population in Norway. The patients reported high long-term satisfaction and continuing effect of VIM-DBS on tremor even after many years. VIM-DBS therefore seems to be an effective symptomatic long-term treatment of ET. However, one patient committed suicide. Only one other suicide has previously been reported after VIM-DBS. It is therefore still unclear whether VIM-DBS increases suicide risk.

Faster cognitive decline in elders without dementia and decreased risk of cancer mortality: NEDICES Study.

OBJECTIVE: To assess whether faster cognitive decline in elders without dementia is associated with decreased risk of cancer mortality. METHODS: In this population-based, prospective study of 2,627 people without dementia aged 65 years and older (Neurological Disorders in Central Spain), a 37-item version of the Mini-Mental State Examination (37-MMSE) was administered at 2 visits (baseline and follow-up, approximately 3 years later). We divided change in 37-MMSE into tertiles (lower tertile ≥ 2 point improvement in score, higher tertile ≥ 2 point decline in score). Community-dwelling elders were followed for a median of 12.9 years, after which the death certificates of those who died were examined. RESULTS: A total of 1,003 (38.2%) died, including 339 (33.8%) deaths among participants who were in the higher tertile of 37-MMSE change and 664 (66.2%) deaths among those in the remaining tertiles. Cancer was reported significantly less often in those in the higher tertile of MMSE change (20.6%) than in those in the remaining tertiles (28.6%): in an unadjusted Cox model, hazard ratio for cancer mortality in participants within the higher tertile = 0.75 (p = 0.04) compared with the participants within the remaining tertiles. In a Cox model that adjusted for a variety of demographic factors and comorbidities, hazard ratio for cancer mortality in participants within the higher tertile = 0.70 (p = 0.01). CONCLUSION: In this population-based, prospective study of community-dwelling elders without dementia, faster cognitive decline was associated with a decreased risk of cancer mortality. Further studies are required to elucidate this inverse association in elders without dementia.

Frailty in elderly persons with essential tremor: a population-based study (NEDICES).

BACKGROUND AND PURPOSE: Essential tremor (ET), one of the most prevalent neurological diseases, has been associated with a variety of comorbidities and, in some studies, a modest increase in risk of mortality. The mechanisms underlying this possible increased mortality have yet to be explored, although one possibility is increased frailty. Frailty has not been studied in ET, and our objective was to address this gap in knowledge. We hypothesized that frailty would be greater in ET cases than in controls. METHODS: A 20-item frailty score assessed comorbid conditions, number of medications, and functional activity. The frailty score was compared in 237 non-demented elderly ET cases and 3903 non-demented age-matched controls from a population-based study in central Spain. RESULTS: The frailty score was higher in ET cases than in controls (8.6 ± 5.2 vs. 6.8 ± 4.6, P < 0.001). Stratifying the frailty score into quartiles and tertiles similarly revealed case-control differences (both P < 0.001). The frailty score also increased with age (r = 0.25, P < 0.001), was higher in women than men (P = 0.02), was correlated with subjective rating of health status (r = 0.42, P < 0.001), and was inversely correlated with body weight (r = -0.06, P < 0.001) and hours/day that participants performed moderate or intensive physical activities (r = -0.16, P < 0.001). CONCLUSION: Essential tremor cases had increased frailty compared to their counterparts without this disease. Whether this increased frailty is a contributor to the increased risk of mortality that has been observed in some studies is a question that deserves further scrutiny.

A population-based study of mortality in essential tremor.

BACKGROUND: Although data are sparse, people with essential tremor (ET) are usually assumed to have mortality rates similar to those in the general population. Because ET is common, particularly among older adults, an influence of ET on the life span would have important public health implications. The authors compared the risks of mortality in patients with ET and control subjects without ET. METHODS: A prospective, population-based design was used to compare the risk of mortality in participants with ET vs controls in three communities in central Spain. Participants were evaluated at baseline (1994 to 1995) and at follow-up 3 years later (1997 to 1998). The relative risk (RR) of mortality (ET vs controls) was estimated using Cox proportional hazards models that excluded participants with Parkinson disease or dementia. RESULTS: Mean baseline age was 73.5 +/- 6.4 years. There were 33 (16.4%) deaths among 201 ET cases and 465 (13.9%) among 3,337 controls. In an unadjusted Cox model, risk of mortality was increased in ET (RR = 1.59, 95% CI = 1.11 to 2.27, p = 0.01). In a Cox model that adjusted for baseline age, gender, educational category, current ethanol drinking, use of antidepressant medication, and community, RR = 1.45, 95% CI = 1.01 to 2.08, p = 0.04. In an adjusted Cox model restricted to persons with longer (>3 years) follow-up, RR = 4.69 (95% CI = 2.18 to 10.07, p = 0.001). CONCLUSIONS: In this longitudinal, prospective study, the risk of mortality was increased in essential tremor. Additional studies of incident cases are needed to confirm these results.