Objectives Anorexia Nervosa (AN) is a leading cause of underweight in children and young people (CYP) in high income countries. Acute cardiovascular complications are well recognised sequelae of underweight in AN, yet less is known about longer term cardiovascular disease (CVD) risk - for example acute MI and stroke later in life. It is now well established that CVD processes leading to disease and death in adulthood begin during childhood. There are a range if important and biological plausible reasons as to why CYP with AN may be at greater risk of CVD later in life. Pulse wave velocity (PWV) is a non-invasive proxy for arterial stiffness (greater PWV indicating greater stiffness) which is well established as a predictive for future adverse cardiovascular disease events in early life.

Methods In this presentation, the potential biological mechanisms and existing evidence for risk of later CVD for CYP in AN will be discussed. Interim, new data from a pilot longitudinal study of PWV in underweight young adolescents with AN admitted to an eating disorder unit in the United Kingdom will be presented. We measured carotid-fem PWV in all new admissions to a single eating disorder unit from December 2020 who met inclusion criteria: 1)Diagnosis of AN;2)Aged 12–18 years;3) underweight (<85% of average BMI for age and sex). PWV was measured using Vicorder by a single operator at admission and weekly for 12 weeks. Ethics approval was provided by a London ethics committee. Standardised PWV Z-score for age (PWVz) was derived from published data.

Results Previous existing data for changes in arterial changes in AN will be presented and biological models. From our study, 16 participants have been recruited so far. Median age 16.3. Baseline median PWV was 7.47 (IQR 7.07–7.94) m/s. Mean PWV z-score was 4. Baseline PWV was not associated with baseline BMI or . In multi-level, mixed effects models PWV decreased over time in weeks (coefficient -0.05,95%CI -0.07 to -0.02). BMI increased in all cases over time (coefficient 0.22,95%CI 0.21 to 0.23. PWV was negatively associated with BMI (coefficient -0.2, 95% CI -0.28 to -0.11).

Conclusions There is emerging evidence of increased CVD risk in later life for CYP with AN. Our data are the first time longitudinal measures of arterial stiffness in CYP with AN have been measured and analysed in a group of CYP with severe AN and underweight, and association to time and weight gain. The preliminary data is suggestive of the positive benefit of weight gain in AN for arterial stiffness, and potentially improving long term life time CVD risk which is an important new focus compared to usual acute cardiac risk consideration. This presentation will discuss the long term implications of CVD risk for CYP with AN through their life and potential biological models for this.