Published studies fulfilling the following inclusion criteria were included in the analysis: were original research; were cross-sectional or longitudinal design; were on patients with probable or possible AD consistent with the Diagnostic และ Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) or the criteria of the National Institute of Neurological และ Communicative Disorders และ Stroke/โรคอัลไซเมอร์ และ Related Disorders Association (NINCDS-ADRDA); reported a prevalence of NPS in AD or sufficient information to calculate an estimate; NPS were assessed by validated scale; sample size at least 50; published in English.