Multimorbidity in Anti-Neutrophil Cytoplasmic Antibody-associated vasculitis: results from a longitudinal, multi-centre data-linkage study

Objectives: ANCA-associated vasculitis (AAV) is considered a chronic, relapsing condition. To date, no studies have investigated multimorbidity in AAV nationally. Here, we characterise temporal trends in multimorbidity and report excess healthcare expenditure associated with it in a national AAV cohort.

Methods: AAV patients diagnosed between 1997 and 2017 were matched with five general population controls. Linked morbidity and healthcare expenditure data were retrieved from a national hospitalisation repository and nationally-published cost data. Multimorbidity was defined as the development of ≥2 disorders. Pre-specified morbidities were analysed individually and together over time using modified Poisson regression, discrete interval analysis and Chi-squared test for trend. The relationship with healthcare expenditure was investigated using multivariate linear regression.

Results: 543 AAV patients (58.7 [48.9-68.0] years; 53.6% male) and 2,672 controls (58.7 [48.9-68.0] years; 53.7% male) were matched and followed-up for 5.1 years. AAV patients were more likely to develop individual morbidities at all timepoints, but especially <2 years post-diagnosis. The highest proportional risk was observed for osteoporosis (adjusted incident rate ratio 8.0, 95% CI 4.5-14.2). After one year, 23.0% of AAV patients and 9.3% of controls were multimorbid (p<0.0001). After ten years, 37.0% of AAV patients and 17.3% of controls were multimorbid (p<0.0001). Multimorbidity was associated with disproportionate increases in healthcare expenditure in AAV patients. Healthcare expenditure was highest for AAV patients with ≥3 morbidities (3.89, 95% CI 2.83-5.31; p <0.001 versus no morbidities).

Conclusions: Our findings emphasise the importance of holistic care in AAV and identify a potentially critical opportunity to consider early screening.