The literature search yielded a total of 20,424 citations: 13,388 from Embase และ 7,036 from PubMed (a total of 16,384 after duplicates removed) (Fig. 1). After the initial screen, 412 studies met the criteria for full-text review, of which 370 were excluded (129 not original research, 85 not AD population, 96 no prevalence or sufficient information to calculate an estimate, 24 no eligible NPS assessment methods, 17 sample size < 50, 19 from same data sources). Additional 6 articles were included by hและ-searching from reference lists of potentially eligible studies. Totally, 48 original researches were included in this