An Ecological Panel Analysis of Trends in the Geographic Disparities of the Certified Nurse and Certified Nurse Specialist in Japan from 1996 to 2022

<b>Background/Objectives</b>: Japan introduced a certification system for Advanced Practice Nursing Workforce (APNW) in 1996. The Japanese Nursing Association formally certified two types of the APNW: Certified Nurses (CNs) and Certified Nurse Specialists (CNSs). Little is known about the geographic distribution of CNs and CNSs. <b>Methods</b>: We conducted an ecological panel analysis using prefecture-level data from 1996 to 2022. To assess the degree of inequality of CN and CNS among prefectures, we calculated the Gini overall coefficients, as well as those by categories of CN and CNS, number of hospitals, number of hospital doctors, and hospital nurses. Using data available from 2000 to 2017, we examined factors associated with CN and CNS density through fixed-effects panel data analyses of log-transformed overall and category-specific densities. <b>Results</b>: During the study period, the number of CNs and CNSs consistently increased, and geographic disparities in their distribution decreased until around 2010. After 2010, however, geographic disparities in prefectures with persistently low CN and CNS densities persisted without significant change. For overall CN and CNS density, significant associations were observed with population aging, per capita income, hospital density, hospital doctor density, hospital nurse density, and study year, whereas hospital nurse wages showed a positive but not statistically significant association. When stratified by clinical category, the directions of associations for several regional factors varied; however, hospital nurse density and hospital nurse wages tended to be positively associated with CN and CNS density in most categories. <b>Conclusions</b>: This study highlighted the need for targeted strategies to increase CN and CNS numbers specifically in prefectures with persistently low densities, tailored to each clinical category.