Nationwide prevalence of rheumatoid arthritis and penetration of disease-modifying drugs in Sweden.

To provide Swedish nationwide data on the prevalence of rheumatoid arthritis (RA), including variations by age, sex, geography, demography and education level, and assess antirheumatic treatment penetration. Patients ≥16 years assigned an RA diagnosis were identified from inpatient (n=96 560; 1964-2007) and specialist outpatient care (n=56 336; 2001-2007) in the Swedish National Patient Register, and the Swedish Rheumatology Quality Register (n=21 242; 1995-2007). Data on prescriptions, demography, vital status and educational level were retrieved from national registers. A total of 58 102 individuals (mean age 66 years; 73% women) assigned an RA diagnosis were alive in Sweden in 2008, corresponding to a cumulative prevalence of 0.77% (women 1.11%, men 0.43%). The 2001-2007 period prevalence was 0.70%. Restriction to patients with ≥2 visits or diagnosis from a rheumatologist/internist reduced the overall cumulative prevalence to 0.68%. Whereas urban/rural differences (crude 0.65-1.00%) were explained by age differences, the age/sex-adjusted prevalence remained higher in patients with ≤9 years education (0.86%) than for those with 10-12 years (0.82%) and >12 years (0.65%). Treatment exposures (76% any disease-modifying antirheumatic drugs (DMARDs) or steroids, 64% any DMARD, 15% biological agents) varied with age; use of biological agents decreased from 22% in 16-59 years olds to 3% in ≥80 years olds. Any DMARD use correspondingly decreased from 71% to 43%. Applying age cut-off points from previous northern European and North American prevalence studies reduced or eliminated between-study differences. This nationwide approach yielded a prevalence of RA similar to previous regional assessments. While displaying only modest geographical variation and no urban/rural gradient, prevalence was associated with educational level. Although most patients received antirheumatic drugs, age was a strong treatment determinant.