Inclusion Criteria:  were 60 years old or older had a normal cognitive function at the time of enrollment, evidenced by a mini-mental state examination (MMSE) score above an education-adjusted threshold (18 for individuals with no school education, 20 for 1-6 years of education, or 24 for 7 or more years of education 27) spoke Mandarin Chinese were able to provide informed consent scheduled for orthopaedic surgeries  Exclusion Criteria:  pre-existing delirium assessed according to the Confusion Assessment Method (CAM) algorithm; prior neurologic diseases (Parkinson's disease, multiple sclerosis or stroke) according to the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10); history of mental disorders, e.g., major depressive disorder and schizophrenia, according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV); unwillingness to comply with the assessments.