Objectives Patients with anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) are at increased long-term risk of cardiometabolic diseases. The prevalence of obesity in AAV has not been well documented. We aimed to characterise change in body weight following a diagnosis of active AAV and to determine the risk factors for this.

Methods We examined data from a single-centre registry of patients with AAV, diagnosed between 2003 and 2023. We evaluated changes in body weight and BMI following diagnosis. Using linear regression, we identified factors contributing to an increase in BMI at six-months. Logistic regression was used to define predictors for obesity at six-months.

Results Two-hundred and fifteen patients with active AAV were included in the analysis. Patients experienced a mean gain in body weight of 5.2% in the first six-months; this was maintained for at least two-years. 64.1% of patients were overweight or obese at six-months. Weight gain was greater following first presentation of AAV compared to relapsing disease. Baseline factors associated with an increase in BMI at six-months included higher eGFR (β=0.70 [0.36-1.03], P<0.001) and earlier year of presentation (β=0.38 [0.08-0.69], P=0.008). Higher eGFR (aOR=1.36 (1.08-2.72), P<0.001) and baseline BMI (aOR=2.57 (1.81-3.64), P<0.001) were associated with an increased likelihood of obesity at six-months.

Conclusion Weight gain is common following a diagnosis of active AAV. This is less pronounced than it was two-decades ago. Better kidney function and higher baseline BMI are associated with a greater risk of being obese at six-months. Management of AAV should include risk mitigation for developing an unhealthy high BMI.

Key messages

Weight gain and an unhealthy high BMI are prevalent following diagnosis of active AAV.

Higher baseline eGFR is associated with greater weight-gain in the first six-months following diagnosis.

Weight gain is less pronounced following treatment of relapsing disease compared to initial presentation.

The authors have declared no competing interest.

There was no monetary support for the preparation of the manuscript.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

We analysed routined collected patient clinical information from electronic health records. The project involved a retrospective audit of data to help improve future patient management and ethics committee approval was not required.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes