Mortality in rheumatoid arthritis: relationship to single and composite measures of disease activity

Background. Rheumatoid arthritis (RA) is a heterogeneous disease characteri zed by a variable course of remissions and relapses. Single measures of dis ease activity at only one point in time may not reflect the overall control of disease activity. Objective. The aim was to determine (i) the predictive value of 20 baseline demographic and disease variables on mortality, and (ii) the relationship between serial measures of the Stoke index (SI; a validated index of diseas e activity in RA) and mortality in RA. Methods. Mortality in 309 RA patients followed up for a median of 14 yr was analysed retrospectively. The standardized mortality ratio (SMR) was calcu lated for all causes of death. The predictive Values of baseline and time-i ntegrated variables were assessed using multivariate Cox proportional hazar ds regression analysis. Results. The SMR was 1.65. At baseline, only nodules, erosions, RA latex ti tre, white cell count and globulin level were predictive of mortality after correction for age, sex and disease duration. Using a stepwise Cox proport ional hazards regression model, the most powerful predictors of mortality w ere age, nodules and RA latex titre. Individual measures of disease activit y and the SI at baseline were not predictive of mortality. However, the mea n level of the SI over 12 months was related to mortality (P = 0.039). Conclusions. At baseline, the demographic and disease variables most signif icantly related to mortality in RA are age, nodules and RA latex titre. Ind ividual measures of disease activity at a single point in time are poor pre dictors of mortality in RA. However, measurement of the mean level of disea se activity over time using the composite SI has a significant relationship with mortality. A high level of sustained inflammation appears to be an im portant predictor of premature death.