Onset of comorbidities and flare patterns within pre-existing morbidity clusters in people with gout: 5-year primary care cohort study

Objective To investigate the onset of comorbidities and pattern of flares over 5 years according to baseline comorbidity clusters in people with gout. Methods In a prospective primary care-based cohort study, adults aged >= 18 years with gout were identified from primary care medical records in 20 general practices across the West Midlands, UK and followed up over 5 years. Four clusters of participants have been defined previously according to baseline comorbidity status. The associations of (i) incident comorbidities and (ii) gout flares with baseline cluster membership were estimated using age and sex-adjusted Poisson regression and mixed effects ordinal logistic regression, respectively. Results The comorbidity with the highest incidence was coronary artery disease (39.2%), followed by hypertension (36.7%), chronic kidney disease stage >= 3 (18.1%), obesity (16.0%), hyperlipidaemia (11.7%), diabetes (8.8%) and cancer (8.4%). There were statistically significant associations observed between cluster membership and incidence of coronary artery disease, hyperlipidaemia, heart failure and hypertension. In each cluster, nearly one-third of participants reported two or more gout flares at each time-point. History of oligo/polyarticular flares (odds ratio [OR]= 2.16, 95% confidence interval [CI]: 1.73, 2.70) and obesity (1.66, 95% CI: 1.21, 2.25) were associated with increasing flares whereas current use of allopurinol was associated with lower risk (0.42, 95% CI: 0.34-0.53). Cluster membership was not associated with flares. Conclusion Substantial numbers of people in each cluster developed new comorbidities that varies by cluster membership. People also experienced multiple flares over time, but these did not differ between clusters. Clinicians should be vigilant for the development of new comorbidities in people with gout.