High prevalence of Parkinson's disease in the Faroe Islands

We used several case-findings methods and strict criteria for case ascertainment to diagnose parkinsonism and idiopathic Parkinson's disease (PD) in the Faroe Islands. In the last few years before the prevalence date of July 1, 1995, we searched various registries from pharmacies, hospitals, and general practices, and found 195 patients with suspected parkinsonism out of 43,709 inhabitants. After excluding those who died before the prevalence date or were treated with levodopa (LD) for other diseases, a total of 124 patients remained for study, of whom 122 participated. We found 102 patients with parkinsonism and 82 with PD versus the expected 53 (p < 0.001, age-specific prevalences in the county of Rogaland, Norway). The overall prevalence of PD was estimated to be 187.6 and the age-adjusted prevalence to be 183.3 versus 110.9 per 100,000 inhabitants in the county of Rogaland. Compared to the study from Rogaland, the mean age at onset of PD symptoms, the mean age at the prevalence date, and the duration of PD indicated that the higher prevalence was not due to either an early onset nor to a longer duration of PD. A lower proportion of definite PD, a lower mean score on the Hoehn-Yahr scale, and a lower average dose of LD suggest that the high prevalence may be due to early diagnosis and a higher ascertainment of cases with mild disease. However, a high incidence cannot be excluded.