Midregional Proatrial Natriuretic Peptide (MRproANP) is associated with vertebral fractures and low bone mineral density (BMD) in patients with COPD

<bold>Background:</bold> Patients with COPD are often affected by BMD loss and osteoporotic fractures. Natriuretic peptides (NPs) are best known as cardiac markers, but have been shown to be associated with low-energy fractures in elderly patients. We aimed to investigate the association between NPs, vertebral fractures and BMD in patients with COPD. <bold>Methods:</bold> Participants of the COSYCONET cohort were analysed. Mean BMD on CT as a risk factor for osteoporosis was assessed at the level of TH12 (AI-Rad Companion). Vertebral fractures were visually quantified by two readers. The relationship between fractures, BMD, NT-proBNP, MRproANP, MRproADM and COPD severity was determined using group comparisons and multivariable analyses. <bold>Results:</bold> A total of 418 participants (median age 64y, FEV1 59.6% pred., 58% male), were included. Vertebral fractures were found in 76 patients (18.1%). Compared to patients without fractures, participants with fractures had elevated levels (p≤0.005) of MRproANP and MRproADM. In multivariate analyses, MRproANP ≥65 nmol/l (OR 2.34; p= 0.011) and age (p=0.009) were the only significant predictors of fractures after adjustment for sex, BMI, smoking status, FEV1 % predicted, SGRQ Activity score, physical activity, oral corticosteroids, the diagnosis of cardiac disease and renal impairment. Correspondingly, age (p=0.055), SGRQ Activity score (p=0.061), active smoking (p=0.025) and MRproANP (p<0.001) were associated with BMD. <bold>Interpretation:</bold> MRproANP can be considered as a marker for osteoporotic vertebral fractures in COPD patients. The association with reduced vertebral BMD are suggestive of direct effects on bone mineralization.