The prevalence of rheumatoid arthritis in the United Kingdom: new estimates for a new century

BACKGROUND: It is 40 yr since the last age- and sex-specific estimates of the prevalence of rheumatoid arthritis (RA) for the UK were published. Since then the classification criteria for RA have been revised and there has been evidence of a fall in the incidence of RA, especially in women. OBJECTIVES: To estimate the age- and sex-specific point prevalence of RA (defined as fulfilment of a modification of the 1987 ACR classification criteria for RA on the day of assessment). The estimate was made in the primary care setting in Norfolk, UK. METHODS: A stratified random sample was drawn from seven age and gender bands. The 7050 individuals selected were mailed a screening questionnaire. Positive responders were invited to attend for a clinical examination. The sample was matched against the names in the Norfolk Arthritis Register (NOAR), a register of incident cases of inflammatory polyarthritis which has been in existence since 1990. RESULTS: The overall response rate was 82%. Sixty-six cases of RA were identified. Extrapolated to the population of the UK, the overall minimum prevalence of RA is 1.16% in women and 0.44% in men. A number of incident cases of RA previously notified to NOAR were not identified as cases in the survey because they had entered into treatment-induced remission. In addition, some cases who failed to attend for examination had significant disability. These prevalence figures are therefore an underestimate. CONCLUSIONS: The prevalence of RA in women, but not in men, in the UK may have fallen since the 1950s.