The under-5 mortality rate (U5MR) refers to the deaths per 1,000 live births under 5 years of age. It is an important statistic for global children’s health and well-being, i.e., access to nutrition and food, housing, and infrastructure, such as water and sanitation, education, property security, access to preventive and curative health services, and future human capital (1). United Nations Children’s Fund (UNICEF) and World Bank have considered reducing child mortality as part of future strategic planning. In addition, reducing U5MR was the fourth Millennium Development Goal (2). The third Sustainable Development Goal (SDG 3) is to reduce the U5MR deaths at least to 25 deaths per 1,000 live 50 births in all countries by 2030 (3).

Despite global efforts to achieve SDG 3 by improving population health over time, child health remains poor in several countries, and geographic inequalities persist between countries with the lowest and highest child mortality rates. The Global Burden of Disease Study 2019 indicated that although global U5MR decreased from 71.2 [95% confidence interval (CI): 68.3–74.0] per 1,000 live births in 2000 to 37.1 (95% CI: 33.2–41.7) per 1,000 live births in 2019, it remained the highest in sub-Saharan Africa, with 74.1 (95% CI: 65.3–85.2) per 1,000 live births in 2019 (1). Moreover, despite that progress, West Africa experienced the highest U5MR with 95.3 per 1,000 live births in 2019 (95% CI: 84.7–109) (1). In addition, the healthy life expectancy was relatively the lowest, and economic development was the poorest in most West African countries (4). Evidently, West African countries are experiencing poorer child health and facing more serious challenges in achieving the SDG on U5MR than other countries. Reducing U5MR and preventing deaths in children has become a global consensus (5), even more urgent for West African countries that are making low progress.

Previous studies have indicated the existence of spatiotemporal variations and identified high U5MR clusters, patterns of progress and geographical inequalities (6). Spatial spillovers are widely recognized in explaining the spatial dependence of subjects to some extent, for example, life expectancy (7) or population aging (8). These studies estimated that three-quarters of the variations can be attributed to temporal or spatial differences between countries in Sub-Saharan Africa (9). For example, an ecological study of China investigated the relationship between the U5MR, geographic, and socioeconomic factors and explored the associated spatial spillovers of the relationship, indicated that the development of economic and medical standards can overcome geographical limits (10). The socioeconomic development in sub-Saharan Africa impacted differently on U5MR, such as the mother’s education level, child sex, family wealth level, and residence (11). In addition, provision of health resources and services guarantees the promotion of children’s health. A previous study found that inequality of health resource distribution was significantly associated with higher U5MR, while the quantity of health resources had a statistically insignificant inverse association with U5MR (12). Health resources refer to various factors of production used by the society in providing medical and health services, including human and material resources (12). Health service is a fundamental input to population health status, along with other factors, including social determinants of health (13).Health resources and services were closely related to the U5MR, the core indicators of health system monitoring by the World Health Organization and the United Nations SDG 3c, i.e., the density of physicians, nurses and midwives, and the density of health facilities (3, 14). An ecological study of 46 African countries indicated that promoting socioeconomic development and increasing coverage of maternal health service and vaccination rates exhibited significant negative effects on U5MR (15). Moreover, other prior studies found that health expenditure impacted child health, with a negative correlation between health expenditure, infant mortality rate, and U5MR in West Africa (16). Two non-spatial ecological studies illustrated that increasing the proportion of births attended by skilled professionals, the coverage of diphtheria vaccination, measles vaccination, etc., may improve U5MR (17, 18). Nevertheless, it is important to understand the relationship between geographical elements and the U5MR in space, since different regions have different health resources and services characteristics. However, due to the lack of the refined long-term U5MR data and the gridded data for geographical and health resource and services factors, studies on the spatial relationship between them have seldom been conducted in West Africa.

Spatial spillovers are widely recognized in explaining the spatial dependence of U5MR to some extent and provide an empirical basis for establishing international health cooperation, regional health cooperation, and health resource allocation mechanism. Analyzing the spatiotemporal characteristics of U5MR and the spatial spillover effect of health resources and services can comprehensively explain the long-term trend of health inequality in different countries in this region. It is of great significance to guide regional health planning and formulate regional health policies in West Africa, conducive to reducing child health inequality between and within countries (19). Hence, the present study aimed to describe the spatiotemporal characteristics of U5MR in 15 West African countries from 2010 to 2019 by combining the ecological design of geographic information systems and explore the spatial spillover effects of health resources and services on U5MR from the perspective of spatiotemporal correlation.

Our study examined spatiotemporal trends and impacts of health resources and services by spatial spillover effects during the study period. Overall, U5MR decreased at different speeds, with the AAPCs and APCs being statistically significant in 15 West African countries. The most significant decrease in U5MR occurred in 2013, 2014, and 2015, with several decreased APCs during 2015–2019 being higher than APCs during 2010–2019. Spatial autocorrelation analysis revealed that the global Moran’s I statistic of U5MR from 2010 to 2019 was greater than zero and statistically significant, indicating that global spatial clustering was observed in adjacent countries. However, the local spatial autocorrelation was not statistically significant. The global Moran’s I statistic increased in the study period, indicating the global spatial autocorrelation and clustering trend of U5MR in adjacent countries and regional variations gradually increased. In addition, we explored spatial spillover effects of health resources and services on U5MR in West African countries. Increasing HDI, physicians density, nurses and midwives density, health center density, percentage of infants lacking immunization for diphtheria and measles, and coverage rate of at least one antenatal visit can reduce U5MR in their own and adjacent countries. Meanwhile, a positive correlation was observed between Current health expenditure per capita and U5MR through positive spatial spillover effects.

The U5MR was observed in a long-term downward trend, and significant progress was made in reducing U5MR in West African countries. Since 2000, West African countries signed the United Nations Millennium Development Goal of “reducing the U5MR by two-thirds by 2015,” and the United Nations proposed SDG of “reducing the U5MR to at least 25 deaths per 1,000 live births in all countries by 2030” (28). Specifically, the 2014–2016 Ebola outbreak in West Africa, particularly in Guinea, Liberia (29), Senegal, Sierra Leone (30), Mali, Nigeria, and Senegal (31), led to trends in child mortality. Weak health systems in West African countries have been less resilient to the impact of the Ebola outbreak, contributing to an increase in U5MR (32). Furthermore, our study analyzed the spatial autocorrelation of U5MR. We showed that U5MR presented positive spatial autocorrelation during our study period from the spatiotemporal perspective. The U5MR of the local country was influenced by the U5MR of adjacent countries; the higher the U5MR of adjacent countries, the higher the U5MR of the local country. Few studies have aligned with the previous correlation analysis of inequity on U5MR by distribution (33, 34). However, in this study, we interpreted the existing positive spatial autocorrelation to indicate the inequity; in other words, we identified regional similarity and clustering. Our study also revealed that spatial autocorrelation increased from 2010 to 2019, suggesting that regional clustering on U5MR increased. Recently, relevant United Nations agencies and charities have implemented multi-faceted global health governance, such as the United Nations Population Fund, UNICEF, the World Health Organization, the Joint United Nations Program on human immunodeficiency virus/acquired immunodeficiency syndrome, the World Bank, the Bill and Melinda Gates Foundation, etc., to help Africa reduce the gap of U5MR.

The recent study indicated that efforts to unmask under-5 mortality patterns through several lenses, including high spatial and temporal resolution, socioeconomic decomposition (6, 35, 36). Socioeconomic development has played a key role in improving children’s health. Consistent with the previous ecological study, the HDI was negatively correlated with U5MR (15). From the spatial perspective, the present study demonstrated that the HDI was negatively correlated with U5MR, and the correlation increased through the spatial spillover effects. Interactions from spatial neighborhoods between HDI and U5MR might be explained by the increase in local socioeconomic development, which might decrease the local and adjacent mortality rate. In terms of regional socioeconomic development, as the largest regional economic organization in Africa, the ECOWAS should consider the spatial spillover effects of the socioeconomic development strategy, strengthen cooperation among neighboring countries, and jointly promote regional economy to reduce U5MR.

Adequate and equitably distributed health resources have been critical to improving population health and achieving universal health coverage and SDGs (37–39). The U5MR of West African countries was not only related to the level of their own health human resources but also related to the U5MR of adjacent countries. This finding was consistent with a previous study, which found that in developed countries, a relatively high density of nurses and midwives was associated with lower U5MR (40). However, the level and distribution of health human resources in West African countries have always been factors hindering the development of population health, which not only affected the health level of children in their local countries but also affected the health level of children in adjacent countries. African countries faced enormous challenges in terms of education, personnel training, and quantity and regional distribution of health workers, especially the acute shortage of physicians, nurses, and midwives (41, 42). In 2015, only 11 African countries met the World Health Organization’s minimum density of 22.8 per 100,000 population health workers (including physicians, nurses, and midwives) (43). In 2018, the density of physicians, nurses, and midwives in the World Health Organization African Region was 1.55 per 100,000 population. Only Seychelles, Namibia, Mauritius, and South Africa have made progress in universal health coverage, and the density of physicians, nurses, and midwives exceeded 4.45 per 100,000 people, but not in West African countries (44). In addition to strengthening the training of health manpower, West African countries need to grasp the differences between different countries in formulating health manpower regulation policies to improve children’s health to a certain extent. Previous studies have demonstrated that increasing health expenditure can reduce U5MR, and similar results have been found in East African countries (45). Additionally, Olatunde et al. used a fully modified least squares panel model to determine the long-term negative correlation between current health expenditure (CHE) and U5MR in West African countries from 1991 to 2015 (46). Similar results were found in single-country studies in Nigeria and Ghana, where increased government spending on health significantly improved child mortality (47, 48). However, the above studies did not consider spatial correlation, and the present study filled this gap; per CHE had negative spatial spillover effect on U5MR. In addition to being associated with U5MR in one country, health expenditure may also affect U5MR in adjacent countries.

To achieve the sustainable goal of U5MR, the quality and equity of antenatal care and routine vaccination should be paid attention to. The health services of adjacent countries might affect children’s health in their local countries to some extent. Although the Expanded Program on Immunization was launched by the World Health Organization in 1974, it has facilitated coordinated progress at the national level in routine vaccination (such as diphtheria, tetanus, pertussis, and measles). However, routine vaccination rates in West African countries were still the lowest, accelerating the spread of infectious diseases in adjacent countries, thereby increasing the burden of infectious diseases and U5MR (49). In addition, antenatal care and skilled delivery became the guarantee of maternal and child health, and unequal distribution of antenatal care coverage in West African countries may also increase the U5MR in neighboring countries (50). Therefore, West African countries should make full use of the regional spillover effects mechanism and strengthen medical exchanges and cooperation with neighboring countries to realize the effective supply of local basic medical services.

In summary, West African countries experienced the highest U5MR and the lowest life expectancy globally. Few studies have explored the correlation between health resources and services and U5MR from the spatiotemporal perspective. However, this study had several limitations. First, this study used panel data and cannot infer cause and effect, but it was combined with geographic information systems to provide a more comprehensive understanding of the spatiotemporal characteristics of U5MR and its spatial spillover effects on health resources and services in West African countries. Second, our study was based on secondary databases and might have certain data quality limitations. However, we selected three globally recognized and authoritative databases, the World Health Organization Global Health Observatory, the United Nations Human Development Report, and the HIME Global Burden of Disease Study, to increase the reliability of data. Third, the indicators of health resources and services may not capture the comprehensive interplay of their process toward U5MR; hence, missing variables and potential confounders, such as unsafe drinking water and poor sanitation facilities, were inevitable and may have left some spatial spillover effects unexplained. Unsafe drinking water and poor sanitation facilities might increase U5MR through the spread of infectious diseases (51). Finally, our study did not consider the prediction of the spatiotemporal trend of U5MR in West African countries. To address these shortcomings, establishing the prediction model of influencing factors of U5MR in West African countries from the spatiotemporal perspective should be considered in order to promote regional health and global health development in the future.

We found geographical variations with global spatial clustering of U5MR at country level in West Africa during 2010–2019. Under the spatiotemporal trend analysis, we identified that regional clustering and regional variations on U5MR gradually increased. Meanwhile, based on exploratory spatial data analysis, we interpreted how health resources and services proxies influence U5MR through spatial spillover effects. Increasing the level of economic development and health human resources (especially nurses and midwives), routine vaccine coverage (diphtheria and measles vaccines), antenatal care coverage, and the proportion of births attended by health professionals may not only reduce U5MR in the local country but also in adjacent countries. We suggest that when making regional health policy and intervention cooperation mechanisms, it is necessary for West African regional organizations, such as the ECOWAS and its affiliated organization and the West African Health Organization, to consider the spatial spillover effects between adjacent countries, which is of great significance for improving children’s health, achieving the 2030 SDGs, Africa Agenda 2063, and universal health coverage.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found at: https://www.healthdata.org/gbd/2019; https://www.who.int/data/gho; https://hdr.undp.org.

The article does not contain any studies with human participants or animals performed by any of the authors. Ethical review and approval was not required because this study disclosed no personal information and used public data freely shared by the Global Burden of Disease (GBD) database (https://www.healthdata.org/about/data), the World Health Organization Global Health Observatory (https://www.who.int/data/gho), and the United Nations Human Development Report (https://hdr.undp.org).

MZ and LN designed the study. MZ performed statistical analyses and drafted the manuscript. LN obtained funding and revised the manuscript. All authors contributed to the article and approved the submitted version.

This research was funded Philosophical and Social Science Fund of Hunan Province, China (20YBQ05). The funders played no role in the study design, data collection, data analysis, data interpretation, or writing of the report.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.