The prevalence of essential tremor in rural northern Tanzania C L Dotchin, R W Walker Department of Medicine, North Tyneside District General Hospital, North Shields, Tyne and Wear, UK Correspondence to: Dr C L Dotchin, Department of Medicine, North Tyneside District General Hospital, Rake Lane, North Shields, Tyne and Wear NE29 8NH, UK; catherine.dotchin@ nhct.nhs.uk Received 14 September 2007 Revised 18 December 2007 Accepted 21 January 2008 Published Online First 13 March 2008 ABSTRACT Introduction: Estimates of the prevalence of essential tremor (ET) vary widely but there are few existing data on the prevalence of ET in sub-Saharan Africa. Patients and methods: A door-to-door community based prevalence study of ET was carried out in the Hai district of northern Tanzania (n = 161 071). The screening questionnaire was followed by examination of positive responders and backed up with other case finding methods. Results: 222 patients responded positively to the screening questions and 43 were referred by village elders. 65 (38 men, 27 women) were diagnosed with ET. Mean age was 72 years and mean duration of symptoms was 11.3 years. The crude prevalence rate was 41/ 100 000 and age standardised prevalence compared with the UK population (2001) was 82/100 000. Discussion: This is the first community based prevalence study of ET in sub-Saharan Africa. Previous data from community based neurological surveys showed lower prevalence rates of 5/100 000 in Ethiopia and 10/100 000 in Nigeria. Non-selective b blockers are available locally and are affordable, yet none of these patients had previously been on any treatment. Estimates of the prevalence of essential tremor (ET) vary widely but there are few existing data on the prevalence of ET in sub-Saharan Africa (SSA). 1 Prevalence rates of ET in previous studies have ranged from 0.05 2 to 220/1000 of the population. 3 A recent study in Italy reported age and sex adjusted prevalence rates of 1.2% for women and 1.9% for men. 4 Previous studies in SSA investigated all neurological diseases, not just ET. Two cases were reported in Nigeria from a population of 20 000, giving a crude prevalence rate of 10/ 100 000, 5 and three cases in Ethiopia 2 in a popula- tion of nearly 61 000, giving a crude prevalence rate of 5/100 000. Age standardisation of rates were not reported. Neurological disease in SSA is a somewhat neglected topic and few data exist on the burden of disease. 6 There are very few consultant neurol- ogists to serve this large population 7 (two for 36.5 million people in Tanzania), meaning that the large majority of the disease burden is likely to be undiagnosed. Hospital based studies detect only the tip of the iceberg: a study by Bower and colleagues 8 found only nine cases of ET in a series of patients from a university hospital neurology clinic in Ethiopia over 1 year. This is likely to be due in large part to poor access to hospital services for the majority of this population, but also because people who are not limited by their symptoms do not seek help. We carried out a door-to-door community based study in a population of approximately 161 000 people in rural Tanzania. PATIENTS AND METHODS The Hai district of northern Tanzania has been a disease surveillance site (DSS) for almost 20 years. Initially it was selected to be representative of a rural, more affluent Tanzanian population for the Adult Morbidity and Mortality Project, organised by a partnership between the Tanzanian govern- ment and Newcastle University, UK. More recently it has been the site of a stroke incidence study (TSIP) 9 and reliable up to date demographic data exist. The Hai DSS has been described previously. 10 At the beginning of the study a census was carried out together with a screening ques- tionnaire to detect tremor. Ethics approval was obtained from the National Institute of Medical Research in Tanzania and the Newcastle and Northumberland Joint Ethics Committee. The following screening questions were used to detect potential cases of ET: c Do your arms or legs shake, apart from maybe when you have drunk alcohol? c Does your head shake? Four further questions were asked to try and specifically detect parkinsonism: 1. Has anyone ever told you that you have Parkinson’s disease? 2. Do you shuffle your feet and/or take tiny steps when you walk? 3. Do you move more slowly than other people your age? 4. Do you have difficulty standing up, or fall easily apart perhaps when drinking alcohol? All people responding positively to either of these questions were examined by the research doctor, either in their own home or at a local dispensary. In addition, other overlapping methods of case ascertainment were used. These were: village elder reporting of people with tremor who had not responded positively to the screening questions and review of neurology outpatient clinic lists of an Irish consultant neurologist who had recently worked at the local consultant referral hospital, Kilimanjaro Christian Medical Centre. ET was diagnosed in patients with a postural or kinetic tremor of the upper limbs, and/or an isolated head tremor, with no other focal neurol- ogy. 11 Information was collected on asymmetry of tremor, resting component, response to alcohol, family history of tremor (in first degree relatives), duration of symptoms and medication. Research paper J Neurol Neurosurg Psychiatry 2008;79:1107–1109. doi:10.1136/jnnp.2007.134304 1107