Looking back: rheumatoid arthritis--aetiology, occurrence and mortality.

Kellgren and Lawrence performed the first studies of the incidence and prevalence of rheumatoid arthritis (RA) in the UK. These have since been updated in Norfolk. The current annual incidence is 36/100,0000 in women and 14/100,000 in men. The prevalence is 0.8% of the adult population. The incidence, prevalence and mortality of RA have fallen in women in the last 50 yr. Excess mortality is predominantly due to cardiovascular disease. Risk factors for the development of RA include obesity, smoking, high red meat consumption, a previous blood transfusion and an adverse pregnancy outcome. Protective factors include the oral contraceptive pill and adequate fruit intake.