Ada Neurol Scand 1995: 91: 79-88 Printed zyxwvutsrqponm in Belgium zyxwvutsrqponm - all rights reserved Copyright zyxw 0 Munhgaard 1995 zy ACTA NEUROLOGICA SCANDINAVICA ISSN 0001-6314 High levodopa use in periodically time-clustered, Icelandic birth cohorts. zy A vestige of parkinsonism etiology? de Pedro-Cuesta J, Petersen IJ, Stawiarz L, Gudmundsson G, Gudmundsson G, Almazh J, Tulinius H, Johansson H, for the Europarkinson Preparatory Activity Research Group. High levodopa use in periodically time-clustered, Icelandic birth cohorts. A vestige of parkinsonism etiology? Acta Neurol Scand 1995: 91: 79-88. zyxwvut 0 Munksgaard 1995. We evaluated levodopa use (LDU) by the Icelandic population focusing on: 1) annual gross levodopa (LD) sales from wholesalers to pharmacies for the period 1978-1990, using a reported method; 2) data from a prescription survey conducted from October lst, 1990 to March 31st, 1991; and 3) raw and reported data on prevalences of Parkinson’s disease (PD) in 1963 in this country. The standard for adjustments and reference population for LDU comparisons was the Swedish in 1984. Crude gross sales of LD in Iceland in 1990 and in Sweden in 1984 amounted to 1.67 and 1.35 DDDil000 person days respectively. After respective adjustments for age, and for age and the infant mortality rates, taken as an indicator of health care quality, LDU in Iceland in 1990 was found to be 1.82 and 1.63 (95% CI 1.47-1.89) times that for Sweden. Prevalences of LD-prescription recipients in 1990-1991 and of PD in 1963 increased with age: however, those of drug users were higher than those of PD among the elderly. Higher-than-expected prevalences of PD and LD-prescription users (there being a partial overlap between these two categories) were found in periodically-clustered, one-year birth cohorts. These results support the notion that Iceland has a high LDU and suggest that this variation is due to a high prevalence of LD responsive disorders. Cohorts born after registered whooping cough outbreaks in Iceland may account for the magnitude and birth-related pattern of PD prevalences and LDU levels. The purpose of evaluation of levodopa use (LDU) by specific populations is to uncover modifiable health-related factors underlying differences in crude LDU (1). A simultaneous approach to the study of levodopa (LD) consumption and Parkinson’s dis- ease (PD) frequency in Iceland deserves particular attention for several reasons: a)gross sales of levodopa for the Icelandic population and in the Faroe Islands are the highest reported to date (1-3); b) 1963 PD prevalence was the subject of research based on a population survey zyxwvut (4); c) when a com- parison was run between incidence or prevalence of PD in the under-70 age group and equivalent figures for the same age group taken from other surveys world-wide, the Icelandic figure exceeded all of these (5-7); and d) high model-based comparative LDU levels have been found in other small, geographically zyxwv J. de Pedro-Cuesta ’,*, I. J. Petersen3, L. Stawiarz’, G. Gudmundsson4, G. Gudmundsson4, J. Almazan’, H. Tulinius5, H. Johansson‘, for the Europarkinson Preparatory Activity Research Group ’ Unit for Neuroepidemiology Division of Neurology, Huddinge University Hospital, Karolinska Institute, Sweden, Department of Applied Epidemiology, National Centre for Epidemiology, Carlos 111 Institute of Health, Madrid, Spain, Pharmaceutical Division, Ministry of Health, * Department of Neurology, National University Hospital, Department of Social and Preventive Medicine, Reykjavik University, Reykjavik, Iceland, National Corporation of Swedish Pharmacies, Stockholm, Sweden Key words: epidemiology; etiology; drug use; levodopa: Parkinson’s disease; whooping cough; quality assessment: pertussis; therapy Jesus de Pedro-Cuesta, lnstituto de Salud Carlos 111, Centro Nacional de Epidemiologia. Departamento de Epidemiologia Aplicada, c/ Sinesio Delgado 6, 28029 Madrid, Spain Accepted for publication June 14, 1994 isolated, Nordic populations, such as Greenland and the Faroe Islands (3). This study seeks to describe antiparkinsonian drug (APD) consumption and to evaluate LDU in Iceland during the period 1978- 1990. Comprehen- sive health care services in Iceland are provided by a public system covering the entire population, and by private practitioners. A medical prescription is required to obtain APDs. When prescribed for treat- ment of PD, APDs were delivered at low cost to Icelandic residents during the study period. Methods Taxonomy and drug use measurements - The Phar- maceutical Division of the Icelandic Ministry of Health provided us with dates of introduction of 79