Depressive symptoms were a common risk factor for pre-frailty and frailty in patients with Alzheimer’s disease

•Investigate associated factors with frailty in patients with Alzheimer’s disease.•The prevalence of frailty was 15.9%.•Depressive symptoms were a common risk factor for pre-frailty and frailty.•Hemoglobin levels and usual gait speed were associated with being frail.•Approached from both physiological and psychological aspects to prevent frailty. This study aimed to investigate factors associated with frailty in patients with mild to moderate Alzheimer’s disease (AD). One hundred fifty-seven outpatients aged 65 years or older with mild to moderate AD were enrolled from January 2018 to December 2018. Cognitive status, depressive mood, activities of daily livings (ADLs), body mass index, handgrip strength (HGS), usual gait speed (UGS), and serum levels of 25-hydroxyvitamin D, hemoglobin (Hb), albumin, and creatinine were assessed. Frailty was defined as a clinical syndrome in which three or more of the following criteria were present: fatigue, resistance, ambulation, illness, and unintentional weight loss. The prevalence of frailty was 15.9%. Those classified as being frail were significantly older, had worse cognitive function, worse ADLs, slower UGS, and lower level of Hb compared to those classified as being pre-frail and those robust, respectively. The pre-frail group was significantly older, had worse ADLs, and slower UGS compared to the robust group. Both the frail and pre-frail groups had more depressive symptoms and weaker HGS than the robust group. Multiple logistic regression analysis showed that cognitive function, UGS, level of Hb, and depressive symptoms were associated with frailty, and that only depressive symptoms were associated with pre-frailty. Depressive symptoms were a common risk factor for pre-frailty and frailty in patients with AD. Hb levels and UGS were associated with being frail. Preventing frailty in patients with AD should be approached from both physiological and psychological aspects.