Discussion
Population-based cohort data from a demographic surveillance site in Eastern Uganda suggest that the postneonatal under-5 mortality incidence rate decreased by 60% in periurban areas between 2005 and 2015. The rural cohort did not witness a similar decrease in mortality as the periurban cohort did. BCG vaccination was associated with a reduced mortality incidence with a larger effect in periurban than rural areas. Household socioeconomic status had an effect on mortality in rural areas only. The proportion of households in the poorest quintile in community was significantly associated with mortality for rural residents only. In both periurban and rural areas, the community maternal education was associated with decreased mortality. The variability between villages was larger in periurban areas than rural areas and much was explained by the level of maternal education in the community.
Population-based vital statistics is hardly available in resource-poor countries due to weak civil registration systems, making it difficult to validate our data. Large national surveys such as the DHS can be used to help understand a mortality trend. A steady decline of postneonatal under-5 mortality in both rural and urban areas of Uganda was observed from data reported in the recent three DHSs, from 89 deaths per 1000 postneonatal children (1996–2006), to 48 deaths (2001–2011) and further down to 34 deaths (2006–2016) in urban areas and from 124 deaths (1996–2006), to 83 (2001–2011) and finally down to 51 (2006–2016) in rural areas. With regards to the Eastern central region or Busoga region of Uganda where our study site is located, the postneonatal under-5 mortality rate decreased from 85 deaths per 1000 postneonatal children (2001–2011) to 58 (2006–2016) (online supplemental appendix 7). In line with the overall regional mortality trend, our data showed an overall decline in postnatal under-5 mortality. Our analysis disaggregating rural and periurban areas showed a slow overall decline in the HDSS which may be attributable to the lack of decline in rural parts of the HDSS. Our data also suggested that the poorer two quintiles experienced a stagnation. While two-thirds of the population live in rural areas in our study site, the proportion of the rural sample included in the DHS sample in Eastern central or Busoga region is not reported in the DHS. While we observed a fluctuation in mortality over the study period, such a trend was not reported in DHS. Available social autopsy data suggest that the rise in mortality in 2010–2011 may be attributable to an increase in deaths due to anaemia but the lack of clinical data does not allow us to draw a conclusive statement.
BCG vaccination status is likely correlated to utilisation and accessibility of other preventive and curative health service, as BCG vaccination is usually given in health facilities. This partly explains a reduced risk of mortality among BCG vaccinated children. In addition, increasing evidence suggests BCG vaccine has non-specific effects on child survival, protecting vaccinated children from infections beyond tuberculosis (TB).26 Our study did not attempt to clarify to what extent vaccinated children had a reduced mortality from TB or other causes. But based on existing evidence and a very small proportion of under-5 deaths from TB in Uganda, it is likely that those who received BCG vaccine were protected against non-TB infectious diseases. Further, it has been suggested that BCG-vaccinated children with scar had a more than 50% reduced risk of mortality compared with vaccinated children with no scar and the reduced mortality among those with a scar could not be explained by deaths due to TB alone.27
A significant disparity between the wealthiest and the poorest was reported in the recent Ugandan DHS, which did not differentiate between rural and urban areas. Our results suggest that household wealth has a much larger effect in rural areas than in periurban areas. Prior studies conducted in sub-Saharan Africa can shed light on our findings. A study using Kenyan DHS data found an association between household wealth and under-5 mortality in rural areas but not in urban areas,28 suggesting that a household wealth has a greater effect on health outcomes in rural areas than in urban areas. On the contrary, a study investigating the association between household wealth and the risk of child mortality using data from the Nouna HDSS in rural Burkina Faso reported that household wealth was a predictor of child mortality in semiurban areas but not in rural areas, contrasting results to our findings.29 Schoeps et al attributed the lack of association between household wealth and child mortality in rural areas to the homogeneity of rural household materials and assets, which might have ‘prevented adequate distribution of households into wealth quintiles’.29 Schoeps et al’ follow-up study in 2015 found decreasing disparities in infant mortality between the most disadvantaged and least disadvantaged groups in the Nouna HDSS.30 They attributed it to improved geographical and financial access to health services and increased coverage of key interventions such as vaccinations, insecticide-treated bed nets and artemisinin-based combination therapies. The much smaller effect of household wealth we found in periurban areas could be an indication of a decreasing disparity in geographical and financial access to health services in periurban areas. Yet, we cannot rule out that the distribution of households into wealth quintiles using household assets and facilities may not capture socioeconomic differentials of periurban residents. In particular, many periurban households may have been classified to be wealthier than they ought to be because of the availability of publicly provided assets such as piped water which were included in the construction of our wealth quintiles. There are alternative methods to construct wealth indices, apart from PCA.31 However, the choice of indicators to measure socioeconomic status appear to have an influence on the extent of socioeconomic disparities in health outcomes32 rather than the methods used. Further research may be warranted using alternative indicators of socioeconomic positions to clarify the relationship between socioeconomic position and under-5 mortality in periurban areas.
In congruence with existing literature, community characteristics were found important predictors of child mortality in our rural district site. An increase by one SD in the proportion of mothers completing primary education in community was associated with a 17% and 12% decrease in mortality in periurban and rural areas. In rural areas, an increase by one SD in the proportion of the poorest household was associated with a 8% increase in mortality. However, community characteristics that seemed more directly associated with risk of morbidity such as the proportion of households with improved sanitation or improved water was not associated with child survival suggesting that human and economic development, both of which provide more opportunities for life and more skills needed to live a decent standard of living, may be a more important contributor to child mortality reduction.
In fact, multiple studies suggest that development across a range of sectors played a role in the reduction of under-5 mortality during the MDG era in low-income and middle-income countries.33 34 The under-5 mortality decline in China was attributed to social progress including maternal education.35 Ethiopia’s success story can be attributed to its government’s multisectoral policies aimed at achieving progress in all the MDGs. Its health sector development plans aligned with the development policies, aiming at the expansion of health services to rural communities.36 A case study of Tanzania also suggested that an economic growth and other related ‘secular trend’ likely influenced child survival positively, including maternal education.37 Malawi’s case study also acknowledge the role of social progress in under-5 mortality.38 In the case of Bangladesh, gender equality appears to have played an important role to its success.39
Results of the studies have important policy implications. A multisectoral development together with strategic efforts to increase the coverage of proven, cost-effective interventions may help increase mortality reduction. Among policy options are those related to economic, social and human development, and human rights.40 Inequities between the poorest and the less poor particularly in rural areas need to be addressed. Individual and household poverty operate through a number of pathways to impact child health in developing countries, from nutrition, access to preventive and curative care, environmental factors (eg, food, water, air, insect vectors) and maternal factors.41 42 Contextual or community factors also operate through individual socioeconomic status to have an impact. Strategies and policies to increase intervention coverage among the poor and the marginalised in rural areas include task shifting and removal of financial barriers.43
The strength of the study is the use of population-based data including both periurban and rural areas for 10 years corresponding to the final 10 years of the MDG era. Cross-sectional data such as DHS and Multiple Indicator Cluster Surveys (MICS) used to estimate mortality rate in low-resource setting can provide a snapshot of an event occurring over a certain period, usually a 5-year period (though shorter periods may be possible44). The HDSSs established in rural areas of resource-limited countries can fill the information gap with more frequently updated data capturing an event occurring in a shorter period. With the longitudinal data, it was possible to observe a yearly trend and determinants over a long period. Results of our population-based study are likely generalisable to other village periurban or perirural areas in Uganda. The study also had limitations. In order to be registered in the HDSS, one must reside in the area for 4 months. Recent migrants and transient population may have been excluded, who might have lowered our mortality estimates, particularly in periurban residents. Previous studies suggest that migrants, particularly rural to urban migrants, have poorer health outcomes than non-migrants.45 It is possible that the areas classed as periurban at the beginning of the study in 2005 expanded over the study period and the boundaries between periurban and rural areas may have shifted. This may have led to misclassification of exposure status and overestimates of risk associated with BCG in the periurban cohort in our studies. Other limitation includes the use of the socioeconomic index which was a measure of relative wealth rather than an absolute measure, based on household facility and asset ownership. Where residents are homogenous, the index may not have captured differentials accurately, leading to the mortality ratio between the poorest and the least poor to unity. Analysis of data on health service utilisation and causes of death would have clarified what contributed to mortality reduction but due to the lack of reliable data during the study period, it could not be incorporated.