Abstract
Advance Directives (ADs) are essential in end-of-life care, enabling individuals to retain autonomy when they can no longer make decisions. However, data on ADs prevalence and influencing factors in different populations (acutely ill, chronically ill, and general) remain limited globally. This review aims to assess the prevalence of ADs in acute and chronic care settings and the general population and identify factors influencing their completion. A systematic review was conducted using PubMed, Scopus and Cochrane Library databases for English-language studies on ADs prevalence up to December 2023. The Joanna Briggs Institute Critical Appraisal Tool was adopted for bias assessment, and information on potential moderating factors-such as age, gender, income, education, marital status, capacity for self-determination and cancer diagnosis-was collected. Analysis involved a random-effects meta-analysis, subgroup evaluations and meta-regressions, with multimodel inference for multivariate assessment. Out of 239 studies covering 8.9 million people, 73.6% were from North America and 18% from Europe. The estimated global ADs prevalence was 0.26 [95% CI: 0.23-0.30], with higher rates among chronically ill individuals and the general population. Positive associations with ADs completion were found for age, education level and white ethnicity, while male gender showed a negative association. Key influencing factors were white ethnicity, education and cancer diagnosis. These findings suggest that ADs completion remains low, relatively unchanged over time, and potentially unequal, especially among non-white, less-educated and non-cancer patients. Increased efforts to raise ADs prevalence are needed, particularly in underrepresented groups.