The prevalence of rheumatoid arthritis in the general population of Spain.

OBJECTIVE To estimate the prevalence of rheumatoid arthritis (RA) in the adult Spanish population and to assess its distribution by basic sociodemographic characteristics. METHODS Two thousand nine hundred and ninety-eight adults were selected randomly from the censuses of 20 municipalities. Trained rheumatologists administered a structured interview that included a screening questionnaire for RA. Subjects with a positive screening result were examined according to a standardized protocol. Cases were defined by the 1987 American College of Rheumatology (ACR) criteria adapted to epidemiological surveys. RESULTS One hundred and eighty-six persons (8.5%) had a positive screening result for RA and 11 of these fulfilled the ACR criteria for RA. The estimated prevalence was 0.5% (95% confidence interval 0.25-0.85). The ratios of women to men and of urban to rural were both 4:1. Function and health perception of the cases were significantly impaired, even after controlling for age and sex. CONCLUSION The prevalence of RA in Spain is comparable to that in other Mediterranean countries. RA may be less frequent in rural settings, a finding that merits further research. A significant proportion of RA cases in the community remain undiagnosed despite impaired functional status.