The prevalence of Parkinson's disease in Portugal. A population approach.

Most of the epidemiological studies designed to determine the prevalence of Parkinson's disease (PD) in Portugal were hospital-based and the rates reported were around 1/1000. A sentinel network of general practitioners (GPs) has been in effect in the country since 1989, involving doctors with a relatively stable list of patients. This group of doctors notifies, every week, all the cases of certain selected diseases that may occur among the patients under their surveillance. On average, each doctor is responsible for 1500 to 1800 persons, of all ages and both sexes, whose main descriptive characteristics are known and updated every year. This led us to the idea of estimating the prevalence of Parkinson's disease in the community and to compare the estimated rates with hospital-based rates. One hundred and fifty general practitioners agreed to participate in a cross-sectional study which included a sample of 220,000 persons. The study took place between March and April 1992 and information on 291 PD patients was collected. Results show that among the study population, age-standardized rates were 1.4/1000 for males and 1.3/1000 for females. Sex-specific rates increase consistently with age in both sexes, reaching a level of 9/1000 in the oldest age group, '75 and more' years. These results estimate a higher prevalence of PD than was determined previously through hospital-based studies and allowed us to determine that patients aged 65 years and more are much likely to be followed by their own GP, either because the disease its already controlled and they are specifically seeking medication or because they find it difficult to attend neurology clinics.(ABSTRACT TRUNCATED AT 250 WORDS)