An epidemiologic study of trends in prevalence of rheumatoid factor seropositivity in Pima Indians - Evidence of a decline due to both secular and birth-cohort influences
Objective. Previous population studies have suggested that both rheumatoid factor (RF) production and rheumatoid arthritis (RA) may be declining in occurrence, and. both secular and birth-cohort influences have been implicated. Since Pima Indians have a very high incidence of RA and also have shown recent evidence or a decline in RA, this study evaluated the relative contributions of age, secular,