BACKGROUND Comparing the distribution of all cause or cause-specific child mortality in countries by income and its progress over time has not been rigorously monitored, and hence remains unknown. We therefore aimed to analyze child mortality disparities between countries with respect to income level and progression for the period 2000-2015, and further explored the convergence of unequal income levels across the globe. METHODS Four types of measures were used to assess the degree of inequality across countries: difference and ratio of child mortality rate, the concentration index, and the Erreygers index. To assess the longitudinal trend of unequal child mortality rate by wealth ranking, hierarchical mixed effect analysis was used to examine any significant changes in the slope of under-5 child mortality rate by GDP per capita between 2000 and 2015. RESULTS All four measures reveal significant inequalities across the countries by income level. Compared with children in the least deprived socioeconomic quintile, the mortality rate for children in the most deprived socioeconomic quintile was nearly 20.7 times higher (95% Confidence Interval: 20.5-20.8) in 2000, and 12.2 times (95% CI: 12.1-12.3) higher in 2015. Globally, the relative and absolute inequality of child mortality between the first and fifth quintiles have declined over time in all diseases, but was more pronounced for infectious diseases (pneumonia, diarrhea, measles, and meningitis). In 2000, post-neonatal children in the first quintile had 105.3 times (95% CI: 100.8-110.0) and 216.3 times (95% CI: 202.5-231.2) higher risks of pneumonia- and diarrhea-specific child mortality than children in the fifth quintile. In 2015, the corresponding rate ratios had decreased to 59.3 (95% CI: 56.5-62.1) and 101.9 (95% CI: 94.3-110.0) times. However, compared with non-communicable disease, infectious diseases still show a far more severe disparity between income quintile. Mixed effect analysis demonstrates the convergence of under-5 mortality in 194 countries across income levels. CONCLUSION Grand convergence in child mortality, particularly in post neonatal children, suggests that the global community has witnessed success to some extent in controlling infectious diseases. To our knowledge, this study is the first to assess worldwide inequalities in cause-specific child mortality and its time trend by wealth.

中文翻译：

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世界各国之间全因和特定原因儿童死亡率的不平等是否有所下降？

背景 比较各国按收入划分的全因或特定原因儿童死亡率的分布及其随时间的进展情况尚未得到严格监测，因此仍然未知。因此，我们旨在分析 2000 年至 2015 年期间各国收入水平和进展方面的儿童死亡率差异，并进一步探讨全球收入水平不平等的趋同性。方法采用四类指标来评估各国的不平等程度：儿童死亡率的差异和比率、集中指数和艾瑞格斯指数。为了评估按财富排名划分的儿童死亡率不平等的纵向趋势，采用分层混合效应分析来检验 2000 年至 2015 年间按人均 GDP 划分的 5 岁以下儿童死亡率斜率的任何显着变化。 结果 所有四项指标均显示显着变化各国收入水平的不平等。与社会经济最贫困五分之一的儿童相比，社会经济最贫困五分之一的儿童死亡率在2000年高出近20.7倍（95%置信区间：20.5-20.8），2000年高出12.2倍（95%置信区间：12.1-12.3） ）在 2015 年更高。在全球范围内，所有疾病中第一和第五五分位儿童死亡率的相对和绝对不平等都随着时间的推移而下降，但传染病（肺炎、腹泻、麻疹和脑膜炎）的情况更为明显。2000 年，前五分之一的新生儿后儿童的肺炎和腹泻特异性儿童死亡风险比其他五分之一的儿童高 105.3 倍（95% CI：100.8-110.0）和 216.3 倍（95% CI：202.5-231.2）。第五个五分位数。2015年，相应的比率已下降至59.3（95% CI：56.5-62.1）和101.9（95% CI：94.3-110.0）倍。然而，与非传染性疾病相比，传染病在五分之一收入之间的差距仍然严重得多。混合效应分析表明，194 个国家不同收入水平的 5 岁以下儿童死亡率趋同。结论 儿童死亡率，特别是新生儿死亡率的大趋同表明，国际社会在控制传染病方面取得了一定程度的成功。据我们所知，这项研究首次评估了全球特定原因儿童死亡率的不平等及其按财富划分的时间趋势。