Prevalence of Essential Tremor on Arosa Island, Spain: a Community-based, Door-to-Door Survey

BACKGROUND: The prevalence of essential tremor (ET) is still not well understood and the various studies performed to date have generated highly variable results. Few epidemiologic studies on the prevalence of ET have been reported from Spain. METHODS: A one-stage door-to-door survey was conducted on Arosa Island, northwestern Spain, to determine the prevalence of ET in the population aged 65 years and older. The diagnostic criteria for ET were the presence of non-dystonic head tremor or moderate- to severe-amplitude tremor on at least four tests of the revised Washington Heights-Inwood Genetic Study of Essential Tremor (WHIGET) Scale. RESULTS: A total of 65 individuals with ET (28 males, 37 females) were identified, resulting in a crude prevalence of 8.63% (adjusted rate 8.42%). Prevalence increased with advancing age. There were no significant differences in prevalence between sexes in any of the age groups. Among the prevalent cases, 12.3% (n = 8) had been previously diagnosed. Only 29.2% (n = 19) reported functional disability caused by tremor. A family history of tremor was reported in 35.4% (n = 23). DISCUSSION: The prevalence of ET was higher than that seen in similar populations in Spain and other countries. A high proportion of those with ET were previously undiagnosed. Since Arosa Island has been a relatively isolated area, these results might indicate a predominant role, at least in the elderly, for genetic factors in the development of ET.