Lower respiratory infections (LRI) and upper respiratory infections (URI) are two forms of medical conditions that affect the respiratory system, usually caused by viruses or bacteria.1 Generally, the symptoms of respiratory infections are fever, sputum production, chest pain, cough, headache, nausea, sneezing, stuffy nose, and tachypnea.1 In children, existing studies have demonstrated an association between recurrent respiratory infections and immune system deficiency.2,3 This association has been revealed to have a long-term effect on children’s health because of the interdependence between immunoglobulin classes. Nutrition is essential in producing energy designed to promote all bodily functions in humans. Intake of nutrients lower than the recommended daily value could result in nutritional inadequacy and, when severe, might lead to nutritional deficiencies (ND).4 ND is characterized by a significant decline in nutrients, causing abnormalities in the body’s regular functions, an increase of the risk for infections, intestinal malabsorption, food scarcity, impaired digestion, and persistent vomiting.4 Globally, more than 150 million children were diagnosed with ND,5 and over one million of children mortality were attributed to respiratory diseases during 2019.6 In low-income countries, more than 80 percent (80%) of respiratory illnesses were identified in the children population.6 According to the World Bank, the Republic of Chad (Chad) is one of the low-income countries that presented a highly significant number of mortality in children under five caused by respiratory diseases and ND.7–10 Such alarming findings demonstrate how the health of children under five is fragile and should be considered as a high-level priority in the country. Therefore, there is a necessity of investigating their burden.

Although poorly approached, existing studies11–14 have discussed the relationship between children under five health outcomes and numerous maternal risk factors, such as maternal gynecological diseases (GD), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), heat exposure, maternal disorders (MD), tuberculosis (TB), and malaria, especially in low-income countries. Furthermore, infectious diseases such as TB and HIV/AIDS prevalence in mothers had been actively identified to affect negatively the health and growth of exposed children.13,14 For instance, a Tanzanian study,12 demonstrated that the maternal HIV/AIDS serostatus is an important variable in determining if a child would or not survive up to five years old. Because of the challenge surrounding the quantification of the degree of association between maternal health conditions and children health outcomes, many studies conducted in Chad had simply presented the trends of respiratory diseases or malnutrition in the children population and certain maternal risk factors relative to socioeconomic factors.9–11 To the best of our knowledge, there exists no comprehensive study that specifically evaluated the association between maternal health conditions and Chadian children under five health outcomes. Consequently, the present study aimed at addressing this gap.

To evaluate the burden of a disease in a population, researchers commonly analyzed metrics such as incidence and disability-adjusted life years (DALYs).15 Accordingly, our study investigated the burden of LRI, URI and ND in Chadian children under five by first analyzing the trends of their incidence and DALYs, followed by the determination of their relationship to maternal health conditions classified as risk factors. Additionally, the research will also assess the effectiveness of health policies employed to alleviate the health status of Chadian children under five from 2015 that marked the year of the world new agenda acted in the United Nations summit known as the sustainable development goals (SDGs).16 Because one of the SDGs is ensuring healthy lives and promoting well-being at all ages, this study aspired into providing scientific findings that could contribute in designing specific strategies and public health policies towards the amelioration of children’s health globally.

METHODS

Data source

The data utilized in this study were extracted from the Global Burden of Diseases (GBD) database.17 The age category of children under five was further divided into six distinct age groups of 0-6 days, 7-27 days, 1-5 months, 6-11 months, 12-23 months, and 2-4 years, as delineated by the GBD. Although the data was categorized by age groups, they represented the national level. Data was not presented by the country regions or provinces. Maternal health conditions assessed in this study included the prevalence of gynecological diseases (GD), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), maternal disorders (MD), tuberculosis (TB), hepatitis B (HB), malaria (M), nutritional deficiencies (ND), alcohol use disorders (AUD), and exposure to extreme temperatures represented by the prevalence of heat and cold exposure (HCE). Data pertaining to these variables were downloaded from the GBD database for the period spanning from 1990 to 2021. All rates were expressed for 100,000 people.

The GBD database is under the Institute for Health Metrics and Evaluation (IHME) control in Seattle, Washington State, USA. Primary data sources for GBD include household surveys with complete birth histories, censuses, vital registrations, disease surveillance systems, and sample registration systems. The data utilized for this research are based on GBD data input under the Global Health Data Exchange (GHDx) section in the results tools. Further details are described on the GBD official website.17 Ethical approval was not needed for this study because there was no direct involvement or interaction with human subjects.

Statistical analysis

The present research has three objectives. First, it analyzed the trends of LRI, URI and ND incidence and DALYs in Chadian children between 1990 and 2021. Secondly, the study investigated the relationship between maternal health conditions and the incidence and DALYs of the three medical conditions in children. Finally, the research evaluated the performance of policies implemented to alleviate children health status and well-being in Chad. To accomplish those goals, our study utilized the following statistical analyses.

To assess trends, a regression known as Joinpoint regression is generally used by researchers in different studies.18–22 When applying Joinpoint regression, years with significant changes in the patterns will be identified and the average annual percent change (AAPC) along with their 95% confidence interval (CI) will be expressed. Our study period was between 1990 and 2021. The study utilized the Joinpoint regression software program (version 4.9.0.0, March 2021) from the Statistical Research and Application branch of the U.S. National Cancer Institute Surveillance Research Program to conduct this analysis. Additionally, the equation and algorithm for the Joinpoint regression analysis calculations are described elsewhere.18

Maternal health conditions association: LASSO Regression

After assessing the trends, the study employed independent variables that were all related to the maternal age category (women aged between 15 and 49 years) to evaluate maternal risk factors. Many studies11–14 identified the association between maternal health conditions and children under five health outcome as well. According to the Global Burden of Diseases study findings,17 a high number of mothers are living with many health conditions in Chad. Those maternal conditions that could be represented by the prevalence rates included the maternal prevalence of gynecological diseases (GD), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), maternal disorders (MD), tuberculosis (TB), hepatitis B (HB), nutritional deficiencies (ND), malaria (M), alcohol use disorders (AUD), and heat and cold exposure (HCE) among others. Therefore, the present research utilized those maternal conditions prevalence rates to elucidate their relationship with the incidence and DALYs attributed to LRI, URI and ND in children under five, using a regression model. Before conducting any regression, it is advised to conducted Pearson correlation to identify the link within the independent variables.23 Relatively, the correlation coefficients of the independent variables are presented in the supplementary materials section (Table SI). Strong significant correlation coefficients could be identified among the estimates, which could indicate the presence of multicollinearity, that is commonly discussed when conducting regression analyses.23 In the presence of multicollinearity, the regression estimates could be misleading, making the model less reliable.24,25 Therefore, the present study utilized a penalized regression known as the least absolute shrinkage and selection operator (LASSO) regression to overcome multicollinearity, as recommended and utilized in different existing studies.26,27 It employs penalization procedures to shrink regression estimates completely to zero (0); automatically excluding one of the independent variables from the model, as described by studies executed in different fields.26–28 The algorithm and equation representing LASSO regression are available elsewhere.29,30 In our study, we utilized the optimum search for the penalty value. RStudio 2021.09.0 Build 3.5.1 software was utilized to conduct LASSO regression analysis.

Policies performance: Interrupted time series (ITS) regression

To accomplish the final objective of this study which is the evaluation of the effectiveness of policies implemented to declined the burden of the respiratory infections and ND in children under five, we used Interrupted time series (ITS) regression, as ITS regression has been employed in numerous studies to evaluate the impacts of various interventions.31 The regression (ITS) utilizes a linear model to assess the changes in the dependent variable before and after a specific intervention.32 The determined points when the estimates of a time series present variations from the preceding created patterns are defined as “change points” frequently connected to implementation of policies. Hence, when the model is designed, it includes the variation in the pre- and post-intervention time points. More details on the regression algorithm and its corresponding equations can be found elsewhere.33 In this study, we analyzed raw data covering the period from 1990 to 2021. The pre-intervention period length was defined as the period from 1990 to 2014. The period of the policy implementation was the year 2015. 2016 to 2021 was the period set as the post-intervention period. The statistical analysis was performed using RStudio version 2021.09.0 Build 3.5.1.

RESULTS

As depicted in Figure 1, the trends of the incidence and disability-adjusted life years (DALYs) attributed to lower respiratory infections (LRI) among Chadian boys and girls under five exhibited a decreasing trajectory over the study period (between 1990 and 2021). Among boys and girls, the highest incidence and DALYs patterns were observed in the youngest age group (0-6 days), whereas the lowest figures were identified in the oldest age group (2-4 years).

Figure 1
Figure 1.Trends of the incidence (a) and disability-adjusted life years (DALYs) (b) rates attributed to lower respiratory infections (LRI) among Chadian boys and girls under five between 1990 and 2021.

In Figure 2, the trends in upper respiratory infection (URI) incidence and DALYs among Chadian boys and girls had been illustrated for the same study period. The figure reveal fluctuating patterns of URI incidence across various age groups, with the highest incidence associated with the age group of 12-23 months in boys and girls. Conversely, the lowest incidence was noted in the oldest age group (2-4 years). Additionally, trends of URI DALYs presented a steady pattern for certain age groups, with the highest DALYs observed in boys of 1-5 months and girls of aged 0-6 days age groups. In contrast, the age group of 2-4 years exhibited the lowest URI DALYs throughout the study period.

Figure 2
Figure 2.Trends of the incidence (a) and disability-adjusted life years (DALYs) (b) rates attributed to upper respiratory infections (URI) among Chadian boys and girls under five between 1990 and 2021.

As for Figure 3, it delineated the trends of nutritional deficiencies (ND) incidence and DALYs among Chadian children under five from 1990 to 2021. The trend of ND incidence displayed generally a downward pattern, despite some fluctuations across certain age groups during certain periods. Prior to 2010, the highest ND incidence was primarily recorded in the youngest age group, while the lowest was found in children from the oldest age group. When examining the trend of ND DALYs, both decreasing and steady patterns were observed across various age groups. The highest DALYs pattern was recorded in the age group of 1-5 months, whereas the lowest was identified in children of 0-6 days, followed closely by those of the 7-27 days age group, which exhibited both seemingly steady behaviors in Chadian boys and girls.

Figure 3
Figure 3.Trends of the incidence (a) and disability-adjusted life years (DALYs) (b) rates attributed to nutritional deficiencies (ND) among Chadian boys and girls under five between 1990 and 2021.

Based on the annual average percent change (AAPC) estimates presented in Table 1, the trends of the lower respiratory infections (LRI) incidence and DALYs among Chadian boys and girls under five showed significant declines. Notably, the decline in LRI incidence and DALYs was more pronounced among girls compared to boys, with the most substantial reductions observed in girls aged 12-23 months and 2-4 years for LRI incidence and DALYs, respectively. The trend of upper respiratory infections (URI) incidence remained unchanged, showing a zero percent (0%) change among Chadian boys and girls under five between 1990 and 2021. In boys aged 12-23 months, the trend of URI incidence exhibited an increase. Conversely, URI DALYs declined significantly across all the girls age groups compared to boys. The girls of 7-27 days recorded the most decreasing percentage when considering the respective AAPC values in both genders. In relation to the trend of nutritional deficiencies (ND) incidence, there had been statistically significant declines in boys and girls under five. The most significant decline of ND incidence was in boys of the youngest age group (0-6 days). Similarly, ND DALYs also declined in Chadian children under five, and the AAPC values indicated that the decline of ND DALYs for both boys and girls aged 7-27 days and 2-4 years were respectively similar.

Table 1.Average annual percent change (AAPC) estimates
Variable Period LRI URI ND
Incidence DALYs Incidence DALYs Incidence DALYs
AAPC (95% CI) AAPC (95% CI) AAPC (95% CI) AAPC (95% CI) AAPC (95% CI) AAPC (95% CI)
Boys
0-6 days 1990-⁠2021 -1.2*(-1.2, -1.2) -1.2*(-1.3, -1.0) -0.0 (-0.0, 0.0) -1.0*(-1.1, -0.9) -1.9*(-2.2, -1.5) -0.9*(-1.0, -0.8)
7-27 days 1990-2021 -1.2*(-1.2, -1.2) -2.4*(-2.5, -2.2) -0.0 (-0.0, 0.0) -1.3*(-1.4, -1.1) -1.8*(-2.1, -1.5) -0.5*(-0.5, -0.5)
1-5 months 1990-2021 -1.0*(-1.2, -0.9) -1.4*(-1.4, -1.3) -0.0 (-0.1, 0.0) -1.0*(-1.1, -0.9) -1.6*(-1.7, -1.4) -3.3*(-3.4, -3.2)
6-11 months 1990-2021 -1.2*(-1.3, -1.1) -1.3*(-1.9, -0.7) -0.0 (-0.0, 0.0) 0.0 (-0.6, 0.6) -1.5*(-1.6, -1.4) -3.2*(-3.7, -2.8)
12-⁠23 months 1990-2021 -1.7*(-1.8, -1.7) -1.5*(-2.1, -0.9) -0.0 (-0.1, 0.0) 0.2 (-0.2, 0.7) -0.8*(-0.8, -0.7) -3.8* (-4.2, -3.4)
2-4 years 1990-2021 -1.7*(-1.8, -1.6) -2.3*(-3.0, -1.6) -0.0 (-0.2, 0.0) -1.1 (-0.5, 0.1) -0.8*(-0.8, -0.8) -4.5*(-4.6, -4.3)
overall 1990-2021 -1.2*(-1.4, -1.1) -1.5*(-1.6, -1.4) -0.0 (-0.1, 0.0) -0.6 (-0.8, -0.4) -1.4*(-1.6, -1.2) -3.4 (-3.6, -3.1)
Girls
0-6 days 1990-2021 -1.5*(-1.5, -1.4) -1.0*(-1.1, -0.9) -0.0 (-0.1, 0.0) -0.9*(-1.0, -0.8) -1.5*(-2.4, -0.6) -0.7*(-0.7, -0.7)
7-27 days 1990-2021 -1.5*(-1.5, -1.4) -4.0*(-4.2, -3.8) -0.0 (-0.1, 0.0) -1.9*(-2.0, -1.8) -1.5*(-2.3, -0.8) -0.5*(-0.6, -0.5)
1-5 months 1990-2021 -1.3*(-1.4, -1.3) -1.9*(-2.1, -1.8) -0.0*(-0.1, -0.0) -1.2*(-1.3, -1.0) -1.7*(-2.0, -1.3) -3.5*(-3.6, -3.4)
6-11 months 1990-2021 -1.5*(-1.6, -1.3) -2.0*(-2.4, -1.6) -0.0 (-0.2, 0.1) -1.0*(-1.4, -0.6) -1.8*(-1.9, -1.7) -3.6*(-3.8, -3.3)
12-23 months 1990-2021 -1.9*(-2.0, -1.8) -2.3*(-2.8, -1.8) -0.0*(-0.0, -0.0) -0.8*(-1.2, -0.4) -1.3*(-1.4, -1.3) -4.3*(-4.6, -4.0)
2-4 years 1990-2021 -1.7*(-1.8, -1.5) -2.8*(-3.3, -2.4) -0.0 (-0.1, 0.0) -0.8*(-1.1, -0.5) -1.4*(-1.5, -1.4) -4.5*(-4.7, -4.5)
overall 1990-2021 -1.5*(-1.5, -1.4) -1.8*(-1.9, -1.6) -0.0*(-0.0, -0.0) -1.2*(-1.3, -1.0) -1.5*(-1.9, -1.2) -3.5*(-3.6, -3.4)

DALYs–disability-adjusted life years; LRI–lower respiratory infection; URI–upper respiratory infection; ND–nutritional deficiencies, CI–confidence interval

Maternal risk factors evaluation

LASSO regression analysis conducted to investigate the connection between maternal risk factors and the incidence and DALYs of LRI, URI and ND in Chadian children under five yielded results presented in Table 2.

Table 2.Findings from Least Absolute Shrinkage and Selection Operator (LASSO) regression analysis
Variables β1 β2 β3 β4 β5 β6 β7 β8 β9 R2 (%) MSE
LRI incidence
Boys
0-6 days -0.04 -0.03 1.92 0.50 N/A 0.28 -1.09 -0.01 -0.67 99.93 0.05
7-27 days -0.06 -0.01 1.94 0.23 N/A 0.29 -0.92 -0.03 -0.56 99.23 0.05
1-5 months -0.06 -0.02 1.32 N/A N/A 0.13 -0.38 -0.10 N/A 99.47 0.04
6-11 months -0.05 0.01 1.23 0.03 N/A 0.13 -0.34 -0.06 N/A 99.72 0.02
12-23 months N/A 0.08 1.09 -0.60 0.19 0.15 -0.05 -0.16 0.32 99.72 0.02
2-4 years N/A 0.09 1.33 -1.25 0.34 0.14 0.12 -0.21 0.46 99.51 0.03
0verall -0.05 N/A 1.50 0.23 N/A 0.21 -0.66 -0.07 -0.26 99.76 0.01
Girls
0-6 days -0.16 -0.19 1.00 N/A N/A 0.22 N/A -0.17 N/A 98.70 0.10
7-27 days -0.09 -0.15 1.51 0.08 N/A 0.36 -0.35 -0.04 -0.51 99.44 0.04
1-5 months N/A -0.11 0.89 N/A N/A 0.17 N/A -0.08 N/A 99.60 0.03
6-11 months N/A 0.00 0.81 0.07 0.09 0.02 N/A 0.01 N/A 99.88 0.00
12-23 months N/A 0.11 0.69 N/A 0.22 N/A N/A N/A 0.05 99.72 0.02
2-4 years N/A 0.14 0.83 N/A 0.12 N/A N/A N/A N/A 99.20 0.06
0verall N/A -0.02 0.91 N/A N/A 0.12 N/A -0.06 N/A 99.50 0.03
LRI DALYs
Boys
0-6 days 0.15 0.24 0.90 0.05 0.53 -0.14 0.06 0.35 -0.82 99.85 0.01
7-27 days N/A 0.01 0.29 N/A 0.22 -0.01 0.51 N/A N/ 99.65 0.02
1-5 months 0.10 0.13 0.42 0.79 0.41 -0.52 N/A 0.35 -0.52 99.76 0.01
6-11 months -0.10 0.03 0.16 2.75 N/A -0.49 -0.19 0.74 -1.75 98.83 0.09
12-23 months -0.25 0.05 0.94 0.25 0.08 -0.23 N/A 0.25 -0.16 96.96 0.23
2-4 years -0.02 -0.06 0.31 1.66 N/A -0.24 -0.18 0.22 -0.71 99.07 0.07
0verall 0.15 0.14 0.74 0.24 0.51 -0.17 0.02 0.30 -0.69 99.86 0.01
Girls
0-6 days -0.27 -0.13 1.93 N/A N/A -0.48 N/A 0.15 -0.57 96.82 0.24
7-27 days N/A -0.11 N/A 0.29 N/A 0.20 0.53 -0.10 N/A 99.82 0.01
1-5 months 0.01 0.16 0.17 1.27 0.09 -0.18 N/A 0.25 -0.61 99.73 0.02
6-11 months -0.01 0.02 0.24 1.77 N/A 0.04 -0.27 0.26 -0.98 99.70 0.02
12-23 months 0.00 0.11 0.13 1.40 0.15 -0.23 N/A 0.34 -0.74 99.50 0.03
2-4 years 0.01 0.01 N/A 1.43 0.15 -0.24 N/A 0.21 -0.53 99.53 0.03
0verall N/A -0.02 0.668 N/A N/A N/A 0.35 -0.04 N/A 98.59 0.10
(a)
URI incidence
Boys
0-6 days 0.94 0.63 -0.57 0.68 0.16 -1.18 1.25 0.76 -0.99 99.47 0.04
7-27 days 0.93 0.63 -0.55 0.64 0.19 -1.18 1.23 0.75 -0.98 99.45 0.04
1-5 months 0.85 0.62 -0.58 0.76 0.19 -1.21 1.23 0.76 -1.01 99.41 0.04
6-11 months 0.66 0.64 -0.55 0.55 0.00 -1.27 1.74 0.78 -0.95 99.37 0.04
12-23 months 0.73 0.60 -0.28 -0.54 N/A -1.65 2.60 0.82 -0.68 99.46 0.04
2-4 years 1.04 0.51 -0.19 -0.94 N/A -2.07 2.97 1.01 -0.73 99.29 0.05
0verall 0.84 0.63 -0.43 0.01 0.05 -1.42 2.01 0.81 -0.84 99.43 0.00
Girls
0-6 days 0.52 0.61 -0.21 0.88 0.63 -0.63 0.13 0.45 -0.97 99.79 0.01
7-27 days 0.57 0.61 -0.23 0.73 0.60 -0.66 0.28 0.45 -0.89 99.77 0.01
1-5 months 0.72 0.61 -0.45 0.68 0.45 -0.82 0.62 0.52 -0.80 99.76 0.01
6-11 months 0.77 0.60 -0.52 0.50 0.38 -1.01 1.01 0.60 -0.74 99.61 0.03
12-23 months 0.77 0.64 -0.50 N/A N/A -1.35 2.06 0.74 -0.70 99.37 0.04
2-4 years 1.08 0.41 -0.38 0.10 N/A -2.32 2.41 1.12 -1.03 98.60 0.10
0verall 0.83 0.60 -0.44 0.53 0.31 -1.27 1.24 0.73 -0.94 99.52 0.03
URI DALYs
Boys
0-6 days 0.10 0.07 N/A 0.52 0.23 N/A 0.14 -0.05 N/A 99.72 0.02
7-27 days 0.22 -0.08 0.08 0.30 0.31 0.03 0.09 -0.03 N/A 99.87 0.00
1-5 months 0.16 0.14 N/A 0.77 N/A 0.13 N/A -0.11 N/A 99.13 0.06
6-11 months -0.86 0.28 0.60 2.14 N/A 0.00 N/A 1.09 -2.81 73.23 2.07
12-23 months -0.99 N/A 0.42 N/A -0.24 N/A N/A 0.03 N/A 89.01 0.85
2-4 years 0.33 -0.81 1.54 4.89 N/A -0.88 -4.29 0.39 -2.29 89.00 0.85
0verall 0.08 -0.00 0.01 2.63 -0.00 0.03 -0.88 0.26 -1.11 99.48 0.04
Girls
0-6 days 0.06 -0.10 0.13 0.52 N/A N/A 0.30 N/A N/A 99.30 0.05
7-27 days 0.18 -0.06 N/A 0.35 0.31 0.19 0.01 -0.14 N/A 99.73 0.02
1-5 months 0.13 0.15 -0.27 1.59 N/A -0.15 N/A 0.136 -0.45 99.33 0.05
6-11 months 0.02 N/A N/A 0.33 0.16 0.31 0.15 N/A N/A 98.13 0.14
12-23 months 0.37 -0.02 -0.17 4.24 0.31 -0.47 -1.76 0.73 -2.10 98.31 0.13
2-4 years 0.28 0.08 0.02 2.06 N/A -0.49 N/A 0.48 -1.24 99.10 0.06
0verall 0.09 -0.00 -0.14 1.37 0.02 0.01 N/A 0.10 -0.45 99.61 0.02
(b)
ND incidence
Boys
0-6 days N/A 0.06 -0.67 1.55 0.14 0.38 -0.44 -0.09 0.04 99.93 0.00
7-27 days N/A 0.06 -0.57 1.36 0.10 0.35 -0.31 -0.08 0.07 99.92 0.00
1-5 months 0.06 0.09 N/A 0.56 0.11 0.26 N/A N/A N/A 99.78 0.01
6-11 months 0.05 0.00 N/A 0.76 0.12 0.07 N/A N/A N/A 99.87 0.00
12-23 months 0.02 0.01 0.25 0.39 N/A -0.00 0.04 -0.11 0.36 99.90 0.00
2-4 years 0.00 N/A 0.17 0.73 N/A 0.02 0.04 N/A 0.00 99.91 0.00
0verall N/A 0.08 -0.22 0.76 0.05 0.28 N/A -0.08 0.16 99.89 0.00
Girls
0-6 days -0.07 -0.17 -2.22 4.24 N/A -0.31 -0.46 0.43 -0.61 91.97 0.62
7-27 days -0.07 -0.15 -1.98 3.73 N/A -0.24 -0.31 0.38 -0.47 94.04 0.46
1-5 months N/A -0.06 -0.95 2.06 N/A -0.06 N/A 0.18 -0.17 98.95 0.08
6-11 months 0.13 -0.08 -0.47 1.86 0.163 -0.07 -0.45 0.09 -0.20 99.89 0.00
12-23 months 0.07 N/A N/A 0.86 N/A 0.00 0.04 N/A N/A 99.90 0.00
2-4 years N/A N/A 0.01 0.64 N/A 0.03 0.29 N/A N/A 99.90 0.00
0verall -0.00 -0.11 -1.20 2.75 N/A -0.14 -0.26 0.22 -0.32 98.25 0.13
ND DALYs
Boys
0-6 days 0.24 0.11 N/A 1.00 0.44 -0.41 0.00 0.26 -0.48 99.87 0.00
7-27 days 0.17 0.07 0.15 0.85 0.35 -0.44 0.07 0.19 -0.31 99.87 0.01
1-5 months 0.23 -0.04 N/A 0.46 0.34 0.04 N/A -0.04 -0.00 99.61 0.02
6-11 months 0.27 -0.18 -0.25 1.69 0.45 0.02 -0.67 0.13 -0.60 99.91 0.00
12-23 months 0.21 -0.20 -0.27 1.83 0.29 0.11 -0.68 0.11 -0.57 99.86 0.01
2-4 years 0.22 -0.16 N/A 0.30 0.33 0.18 N/A -0.10 N/A 99.42 0.04
0verall 0.30 -0.19 -0.21 1.67 0.49 0.01 -0.79 0.10 -0.53 99.90 0.00
Girls
0-6 days 0.29 0.08 N/A 0.87 0.52 -0.41 0.01 0.26 -0.44 99.83 0.01
7-27 days 0.29 0.06 0.00 0.88 0.55 -0.43 0.04 0.29 -0.53 99.86 0.01
1-5 months 0.17 -0.06 -0.19 1.03 0.22 0.00 N/A 0.06 -0.29 99.75 0.01
6-11 months 0.07 -0.10 -0.26 1.22 0.02 0.22 N/A 0.02 -0.34 99.89 0.00
12-23 months 0.08 -0.07 -0.31 1.38 N/A 0.21 -0.03 0.04 -0.41 99.86 0.01
2-4 years 0.26 -0.10 N/A 0.18 0.43 0.17 N/A -0.09 N/A 99.45 0.04
0verall 0.08 -0.09 -0.35 1.49 N/A 0.13 -0.00 0.06 -0.43 99.88 0.00
(c)

N/A–not applicable; LRI–lower respiratory infection; URI–upper respiratory infection; ND–nutritional deficiencies; MSE–mean square error; R2–R-square; β1–maternal prevalence of gynecological diseases; β2–maternal prevalence of human immunodeficiency virus/acquired immunodeficiency syndrome; β3–maternal prevalence of maternal disorders; β4–maternal prevalence of tuberculosis; β5–maternal prevalence of hepatitis B; β6–maternal prevalence of nutritional deficiencies; β7–maternal prevalence of malaria; β8–maternal prevalence of alcohol use disorders; β9–maternal prevalence of heat and cold exposure; DALYs–disability-adjusted life years.

When considering the relationship between the incidence and DALYs of LRI and the maternal risk factors included in this study, the R-squared values indicated a strong association exceeding 90 percent (90%). This finding means that more than 90% of LRI incidence and DALYs can be explained by those maternal risk factors. A similar strong relationship was observed over the association between the incidence and DALYs of ND among children under five and maternal risk factors. The association between the incidence of URI and maternal risk factors also demonstrated a strong relationship (over 90%) for both genders. However, 73% and 89% of URI DALYs are explained by the maternal risk factors in boys of 6-11 months, 12-23 months and 2-4 years age groups. In the girls under five, this association exceeded 90%. The mean square error (MSE) values were generally low, except for the interaction between maternal risk factors and URI DALYs in boys aged 6-11 months.

The impact of each maternal risk factor is outlined as the beta values in Table 2. Table 2 (a) displayed the relationship between maternal risk factors and the incidence and DALYs attributed to LRI. When observing the values of beta coefficients across the different age groups, the prevalence of maternal disorders (MD) and the prevalence of maternal nutritional deficiencies (ND) had positive values suggesting a positif impact. This means that the increase in maternal prevalence of MD and ND is associated to an increase of LRI incidence and DALYs in boys and girls under five according to the beta coefficients in Table 2 (a).

Table 2 (b) described the association between maternal risk factors and URI incidence and DALYs in Chadian children under five. According to the respective values of the beta coefficients, maternal prevalence of gynecological diseases (GD), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), malaria (M), and alcohol use disorders (AUD) showed positive values regarding URI incidence in boys and girls under five. This finding underlined that an increase in those maternal health conditions (risk factors) resulted in an increase of URI incidence in Chadian children under five. Moreover, we could notice that maternal prevalence of GD and tuberculosis (TB) increased as URI DALYs also increased in the girls children.

The relationship between maternal health conditions and ND incidence and DALYs are presented in Table 2 (c). Based on the presented values, when maternal prevalence of tuberculosis (TB) increased, the incidence of ND also increased in boys and girls under five. Furthermore, an increase in the maternal prevalence of GD, TB and hepatitis B (HB) resulted in an increase of ND DALYs, particularly in the boys children.

Policies performance

Table 3 displayed the findings from the interrupted time series (ITS) regression analysis, presenting the effectiveness of policies implemented to address the burden of LRI, URI and ND in Chadian boys and girls under five. In this analysis, β1 represents the period prior to the implementation of policies (1990 to 2014), β2 indicates the implementation year (2015), and β3 corresponds to the post-intervention period (2016 to 2021).

Table 3.Findings from Interrupted Time Series (ITS) regression Analysis
Variables Estimates LRI URI ND
incidence DALYs incidence DALYs incidence DALYs
Boys
0-6 days β1 -0.05* -0.06* -0.04 -0.09* -0.07* -0.07*
β2 0.31 0.13 -0.21 -0.03 -0.04 -0.00
β3 -0.44* -0.13 0.26 -0.01 -0.00 -0.02
Adjusted R2 91.35 24.07 1.47 60.19 25.23 19.72
7-27 days β1 -0.05* -0.09* -0.04 -0.10* -0.07* -0.08*
β2 0.31 0.06 -0.21 -0.05 -0.04 0.01
β3 -0.44* -0.04 0.25 0.04* -0.00 -0.06
Adjusted R2 91.33 78.68 1.17 98.99 31.33 31.11
1-5 months β1 -0.07* -0.06* -0.04 -0.08* -0.08* -0.10*
β2 0.17 0.07 -0.19 -0.02 -0.04 0.00
β3 -0.31* -0.13* 0.23 -0.02 -0.02 0.02
Adjusted R2 85.61 20.03 0.29 54.09 48.73 93.62
6-11 months β1 -0.07* -0.06* -0.03 0.05 -0.08* -0.11*
β2 0.13 0.13 -0.17 0.42 -0.04 0.00
β3 -0.28* -0.20 0.20 -0.46 -0.03 0.05*
Adjusted R2 81.97 28.53 -2.04 2.89 65.05 94.54
12-23 months β1 -0.07* -0.04 -0.04 0.12* -0.08* -0.11*
β2 0.07 0.10 -0.22 0.29 -0.04 0.00
β3 -0.20* -0.32* 0.25 -0.50* -0.09 0.05*
Adjusted R2 70.62 37.83 -0.77 56.85 67.97 95.34
2-4 years β1 -0.06* -0.08* -0.06 0.06 -0.09* -0.12*
β2 0.09 0.09 -0.35 0.16 -0.02 -0.00
β3 -0.22* -0.16* 0.36 -0.49* -0.05 0.07*
Adjusted R2 69.16 71.51 3.83 15.11 73.23 69.26
Overall β1 -0.06* -0.07* -0.04 -0.08* -0.08* -0.11*
β2 0.19 0.10 -0.22 0.02 -0.04 0.00
β3 -0.31* -0.11 0.26 -0.11 -0.02 0.04*
Adjusted R2 88.36 35.08 0.85 69.36 44.10 95.74
Girls
0-6 days β1 -0.05* -0.06* -0.04 -0.09* -0.07* -0.07*
β2 0.31 0.13 -0.21 -0.03 -0.04 -0.00
β3 -0.44* -0.13 0.26 -0.01 -0.00 -0.02
Adjusted R2 91.35 1.32 1.47 60.19 25.23 19.72
7-27 days β1 -0.05* -0.09* -0.04 -0.10 -0.07* -0.08*
β2 0.31 0.06 -0.21 -0.05 -0.04 0.01
β3 -0.44* -0.04 0.25 0.04* -0.00 -0.06
Adjusted R2 91.33 78.68 1.17 98.99 31.33 31.11
1-5 months β1 -0.07 -0.06* -0.04 -0.08* -0.08* -0.10*
β2 0.17 0.07 -0.19 -0.02 -0.04 0.00
β3 -0.31 -0.13* 0.23 -0.02 -0.02 0.02
Adjusted R2 85.61 20.03 -0.29 54.09 48.73 93.62
6-11 months β1 -0.07* -0.06* -0.03 0.05 -0.08* -0.11*
β2 0.13 0.13 -0.17 0.42 -0.04 0.00
β3 -0.28 -0.20 0.20 -0.46 -0.03 0.05
Adjusted R2 81.97 28.53 -2.04 2.89 65.05 94.54
12-23 months β1 -0.07* -0.04 -0.04 0.12* -0.08* -0.11
β2 0.07 0.10 -0.22 0.29 -0.04 0.00
β3 -0.20* -0.32* 0.25 -0.50* -0.09* 0.05*
Adjusted R2 70.62 37.83 -0.79 56.85 67.97 94.34
2-4 years β1 -0.06* -0.08* -0.06 0.06 -0.09* -0.12*
β2 0.09 0.09 -0.32 0.16 -0.02 -0.00
β3 -0.22* -0.16* 0.36 -0.49* -0.05* 0.07*
Adjusted R2 69.16 71.51 3.83 15.11 73.23 69.26
Overall β1 -0.06* -0.07* -0.04 -0.08* -0.08* -0.11
β2 0.19 0.10 -0.22 0.02 -0.04 0.00
β3 -0.33* -0.11 0.26 -0.11 -0.02 0.04
Adjusted R2 88.36 35.08 0.85 69.36 44.11 95.74

LRI–lower respiratory infection; URI–upper respiratory infection; ND–nutritional deficiencies; Adjusted R2–adjusted R-square; β1–pre-intervention period; β2–time of intervention; β3–post-intervention period; DALYs–disability-adjusted life years.

Based on the findings, the statistical estimates relative to boys under five indicates that LRI incidence and DALYs exhibited significant negative values across age groups during the pre-intervention period (β1). The negative value of β1 suggested that the existing policies during that period (1990-2014) had a decreasing effect on LRI incidence and DALYs in boys under five. At the time of intervention, only non-significant positive values (β2) were observed in boys and girls children. Accordingly, LRI incidence and DALYs slightly increased in the children under five at the time of the policies implementation. Between 2016 and 2021, β3 estimates were negative in boys and girls under five, with with only significant estimates in the boys. Relatively, LRI incidence and DALYs were impacted by the implemented policies, causing significant decline between 2016 and 2021 in boys children.

When observing the beta coefficients for URI incidence and DALYs, we can notice that (β1) values are positive and negative across the different age groups in Chadian boys and girls under five. The same finding was exhibited at the time of intervention (β2). This means that URI incidence and DALYs in boys and girls children under five alternatively decreased and increased before and during the intervention period. Based on the estimates, we could noticed that β3 values were positive when considering URI incidence in both boys and girls. Except for the age group of 7-27 days, β3 values suggested a decline in the URI DALYs relative to the policies between 2016 and 2021.

Lastly, NDI incidence significantly declined in boys and girls before the intervention period according to the values. During 2015 (intervention time), only ND incidence was declining in the children under five in comparison to ND DALYs. Between 2016 and 2021, ND incidence was affected by the implementation of the policies, resulting in its decrease in Chadian boys and girls under five, when compared to ND DALYs. Moreover, when examining the adjusted R-squared (R²) values, they indicated that some models did not perform well because of possible linearity contrast.

DISCUSSION

The present study evaluated first the trends of lower respiratory infections (LRI), upper respiratory infections (URI), and nutritional deficiencies (ND) incidence and disability-adjusted life years (DALYs) in Chadian boys and girls under five between 1990 to 2021. Secondly, it analyzed maternal risk factors association to the incidence and DALYs of the three medical conditions in the children. Finally, the research assessed the effectiveness of implemented policies regarding the amelioration of the children under five health relative to LRI, URI and ND.

The assessment of the trends showed that LRI and ND incidence and DALYs declined between 1990 and 2021 in children under five from Chad. Remarkably, URI incidence did not decline during this period. The government of Chad, along with various stakeholders, had implemented numerous strategies that aimed at improving the health status of children under five, ameliorating maternal health, enhancing the living conditions for the population, and strengthening the healthcare system, as previously outlined in several studies.34–36 Consequently, the observed decreasing patterns in various trends among children under five might be associated with these concerted efforts over recent decades. Our findings also revealed that URI incidence displayed fluctuations in its trends around the age groups. This observation might be justified by the differences in seasonal outbreaks as reported overtime, and the variability of the impacts generated from efforts made by the Chadian government and its healthcare partners as reported in existing literature.5,37 Moreover, the study demonstrated that trends from DALYs declined mostly in girls under five. This finding might be justified by the higher incidence observed in boys compared to girls from our study, as also discussed in other studies.38,39 Additional efforts are required with a greater commitment to effectively address the health challenges faced by Chadian children. Numerous factors, including socioeconomic and demographic variables, have been associated with the burden of URI in low-income countries.40,41 Thus, the steady trends in URI incidence among the children might stem from the impact of poverty, lifestyle choices, occupational hazards, exposure to biomass fuel, tobacco smoke, sulfur and nitrogen dioxide, dust, or insufficient access to specialized pediatric care.7,38,39 In the presence of such social and environmental conditions, the youngest population (children) are the most exposed because of their weaker immune system in contrast to adults. Consequently, previous studies2,3 have established a link between recurrent respiratory infections and deficiencies in the immune system among children. Accordingly, improving environmental and lifestyle factors, along with implementing a more effective national nutritional program might significantly contribute to alleviating the burden of various diseases and ensuring a healthy development for Chadian children under five.2,3,39

The association between LRI, URI, and ND incidence and DALYs in Chadian children under five, and maternal health conditions was investigated in this study. The study findings revealed that 70% to 99% of LRI, URI and ND incidence and DALYs in the children under five can be explained by the maternal health conditions that represented risk factors. Furthermore, LRI incidence and DALYs increased when maternal prevalence of maternal disorders (MD) and maternal prevention of nutritional deficiencies (ND) also increased. Additionally, in the presence of an increase of maternal prevention of gynecological diseases (GD), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), malaria (M) and alcohol use disorders (AUD), URI incidence and DALYs increased as well. Only maternal prevalence of tuberculosis (TB), GD and hepatitis B (HB) increased as ND incidence and DALYs also increased in Chadian boys and girls under five. Previous studies11–14 have corroborated the connection between maternal health status and the health outcome of children under five. For instance, research from 201742 highlighted the impact of maternal malnutrition on child growth in Pakistan under the influence of certain factors such as sanitation and unhealthy food. Additionally, maternal risk factors such as maternal prevalence of heat and cold exposure, excessive alcohol consumption, and the burden of maternal HIV/AIDS and tuberculosis can adversely affect child health and development by impacting negatively their immune system.11–14,43–46 Therefore, it is important that Chadian health institutions and international organizations systematically develop and implement robust strategies, policies, and laws to improve maternal health status, lifestyle conditions, and healthcare system and services across the country. Programs and campaigns to explain the risks of diseases such as HIV/AIDS and tuberculosis on women of reproductive age and their children should be established or reinforced in different communities. Promoting and ameliorating maternal health might essentially decrease the burden of respiratory diseases and ND in children under five. The identified maternal risk factors in our study should be precisely addressed.

From 2015, the Chadian government in collaboration with different international organizations, developed and implemented various policies targeting the health of children under five relatively to the Sustainable Development Goals (SDGs).16,47 Those policies were established to ameliorate many conditions such as maternal and children health.48 The amelioration of the healthcare quality and system, promotion of community health, and accessibility to vaccins for mothers and children were the main components of policies based on the SDGs.49 Our findings revealed that the implementation of those different policies resulted in a decline of the trends relative to LRI incidence and DALYs among Chadian boys and girls under five. Conversely, these policies did not effectively reduce the incidence and DALYs attributed to URI in either boys or girls. Nonetheless, a decline in ND incidence was observed in both boys and girls under five as a result of the policies impact. Thus, the implemented policies reduced the burden of many medical conditions, including respiratory diseases and nutritional deficiencies, while promoting the safe development of children as mentioned in other studies.50,51 Given the high prevalence of respiratory illnesses in low-income countries,6 there is an urgent need for the improvement of living conditions, promotion of cleaner environments, and educational campaigns targeting both urban and rural populations to significantly reduce respiratory diseases in Chad. Designing special policies that address specific age groups that did not exhibit declining trends may also directly contribute to positively affecting children health outcomes. Furthermore, because many maternal health conditions are identified to have a strong relationship with LRI, URI, and ND incidence and DALYs in children under five, a particular attention should be given to the health of Chadian mothers.

As many other existing studies, the present research also presented limitations. The first limitation of this study is that the extracted data did not provide incidence and DALYs rates by national regions or provinces. Having such data would facilitate the identification of the most vulnerable zones, genders, and age groups. Therefore, our future research will focus on analyzing the incidence and DALYs rates of LRI, URI and ND in Chadian children under five by provinces, gender, and age groups for Geo-spacial and observational study. The second limitation is relative to the regression models that did not perform well and translated by the lower adjusted R-square values or the higher mean standard errors estimates. This observation is generally associated to the data quality. Future studies should be conducted using different dataset to confirm out findings.

CONCLUSIONS

The present study demonstrated that URI incidence did not decline in Chadian children under five between 1990 and 2021. Maternal health conditions were strongly associated to the incidence and DALYs from the three medical conditions. With such significant association of maternal health conditions and children under five health outcome, the present study could serve as an assessment element by healthcare providers when investigating respiratory infections and malnutrition in the population under five. Because the implemented policies only impacted effectively LRI incidence and DALYs, and ND incidence by decreasing their respective trends, new policies should be designed, targeting particularly maternal health, lifestyle as well as living conditions and healthcare system. Such approach might directly contribute positively to the decline of respiratory infections and nutritional deficiencies burden in children under five in low-income countries such as Chad.

Data availability

The datasets analyzed in the current study are available at http://ghdx.healthdata.org/gbd-results-tool.17</a>

Authorship contributions

NTM led to conceptualization and design of the study. NNN, SP, LM, IAK, AG, SK and OAM contributed to the conceptulization and critical suggestions for the design of the study. NTM supported the data collection and conducted data analysis verified by NNN, SP, LM, IAK, AG, SK and OAM. NTM had full access to the data. NTM wrote the manuscript draft. NNN made edits to the draft. SP, LM, IAK, AG, SK and OAM performed critical review and provided suggestions to the manuscript writing. All authors read and approved the submission of the finalized version of the manuscript for publication.

Disclosure of interest

“The authors completed the ICMJE Disclosure of Interest Form (available upon request from the corresponding author) and disclose no relevant interests.”

Additional materials

Additional information is provided in the online supplementary document (appendix).

Correspondence to:

Name Surname Nodjimadji Tamlengar Martial
Institution Centre pour l’Environnement et le Développement Durable (CEDD)
Address N’Djamena, PoBox 788
Country Chad
email@email martialtam@gmail.com