Twenty-four-hour multichannel intraluminal impedance-pH (24 h MII-pH) monitoring is the gold standard for diagnosing gastroesophageal reflux disease. Owing to differences in genetic background, dietary habits, and lifestyle across populations in different countries and regions, the diagnostic thresholds of 24 h MII-pH may also vary among different populations. This article reviews relevant domestic and international literature to summarize current research progress on 24 h MII-pH diagnostic thresholds among different population groups in Asia, North America, Europe, and other regions. Furthermore, this paper conducts an in-depth analysis of regional variations in thresholds and their underlying influencing factors from perspectives including race and genetic background, dietary habits, and lifestyle factors.