Prevalence and risk factors of skeletal muscle loss and sarcopenia in patients with autoimmune pancreatitis

Background: Previous studies have highlighted the frequent occurrence of sarcopenia in patients with pancreatic diseases, including chronic pancreatitis. We aimed to clarify the prevalence of skeletal muscle (SM) loss and sarcopenia, and their associations with clinical characteristics, bone mineral density, and pancreatic imaging findings in patients with autoimmune pancreatitis (AIP). Methods: This study included 114 patients with AIP treated at Tohoku University Hospital. The SM index was assessed using a bioelectrical impedance analysis device, grip strength was measured using a hand dynamometer, and bone mineral density was evaluated using dual-energy X-ray absorptiometry. Univariate and multivariate logistic regression analyses were used to analyze factors associated with SM loss and sarcopenia. Results: Among 114 patients, 57 (50.0%) had SM loss, 31 (27.2%) had reduced grip strength, and 27 (23.7%) had both. Patients with SM loss were older and had a lower body mass index, weaker grip strength, higher Controlling Nutritional Status scores, and lower serum lipase and albumin levels compared to those without SM loss. Computed tomography scans revealed a higher prevalence of pancreatic parenchymal atrophy in patients with SM loss. Similar differences were observed between patients with sarcopenia and those without. Osteopathy was observed in 35.6% of patients with SM loss and 38.1% of those with sarcopenia, whereas only 4.1% of patients without SM loss had osteopathy. Low BMI (< 21.0 kg/m²) was also found to be an independent risk factor for SM loss in multivariate analysis. Age > 72 years, low BMI (< 20.0 kg/m²), and low serum lipase levels (< 13 U/L) were independent risk factors for sarcopenia in multivariate analysis. Conclusions: SM loss and sarcopenia are prevalent in patients with AIP and are associated with aging, poor nutritional status, low serum lipase levels, and pancreatic parenchymal atrophy. In addition to the high risk of osteopathy, careful attention should be paid to maintain muscle health in AIP patients.