Acute Respiratory Infections (ARIs) are the leading cause of mortality and morbidity among children under 5 years old and about 1.3 million annually worldwide. Account for 33% of deaths among children under 5 years that occurred in developing countries. In Cambodia, ARIs prevalence in children under 5 years old was 20% in 2000, and 6% in 2014. Hence, the aimed to describe the trends of ARI symptoms among children aged 0–59 months over time using the 2000, 2005, 2010, and 2014 Cambodia Demographic and Health Survey (CDHS) and determined the relationships between socio-demographic, behavioral, and environmental factors with ARI symptoms. We analyzed existing children’s data from 2000, 2005, 2010 and 2014 of Cambodia Demographic and Health Survey (CDHS) that used a two-stage stratified cluster sampling design. We limited our analysis to children born in the last five years prior to the surveys, alive and living in households during interview time. Data were pooled across the four survey years for 29,171 children aged 0–59 months. All statistics were carried out using STATA V16, and survey weights were taken into account for the survey design of the CDHS. We used multiple logistic regression to determine the main predictors of ARI symptoms among children under 5 years. ARI symptoms in the previous two weeks in children aged 0–59 months in Cambodia were 19.9% in 2000 to 8.6% in 2005 to 6.4% in 2010, and 5.5% in 2014. Factors independently associated with increased odds of ARI symptoms were children ages 6–11 months with adjusted odds ratio [AOR = 1.91; 95% CI: 1.53–2.38], 12–23 months [AOR = 1.79; 95% CI: 1.46–2.20], and 24–35 months [AOR = 1.41; 95% CI: 1.13–1.76], smoking mother [AOR = 1.61; 95% CI: 1.27–2.05], and using non-improved toilets in households [AOR = 1.20; 95% CI: 0.99–1.46]. However, the following factors were found to be associated with decreased odds of having ARI symptoms: Mothers with higher education [AOR = 0.45; 95% CI: 0.21–0.94], breastfeeding children [AOR = 0.87; 95% CI: 0.77–0.98], and children born into richest wealth quantile [AOR = 0.73; 95% CI: 0.56–0.95], respectively. Survey 2005 [AOR = 0.36; 95% CI: 0.31–0.42], 2010 [AOR = 0.27; 95% CI: 0.22–0.33], 2014 [AOR = 0.24; 95% CI: 0.19–0.30]. The trends of ARI symptoms among children under five in Cambodia significantly decreased from 2000–2014. Smoking mothers, young children ages (0–35 months), and using non-improved toilet in household are factors that independently increased the likelihood that children would develop ARI symptoms. Inversely, factors were found to be associated with decreased odds of having ARI symptoms: Mothers with higher education, breastfeeding children, and children born into the richest wealth quantile and Survey years. Therefore, government and child family programs must promote maternal education, particularly infant breastfeeding. The government ought to support maternal education and infant breastfeeding in the interest of early childhood care.

INTRODUCTION Acute Respiratory Infections (ARI) are a public health concern. According to the World Health Organization (WHO), ARI are responsible for 3.5% of all diseases in the world and more than 808,000 (15%) of all under-five deaths worldwide in 2017. ARI continues to be one of the leading causes of childhood morbidity and mortality in Cambodia, children under five of age who had ARI symptoms peaked at 20% in 2000 and have since decreased to 6% in 2014. We aimed to assess the trends over time of ARI symptoms and examine the socio-demographic, behavioral, and environmental factors associated with ARI symptoms among Cambodian children aged 0-59 months across 2000, 2005, 2010, and 2014. METHODS We used existing children data from the Cambodia Demographic and Health Survey (CDHS) with a total of children ages 0-59 months analyzed 7,828 in 2000, 7,621 in 2005, 7,727 in 2010, and 6,864 in 2014, respectively. All estimations were carried out using STATA V16, within the survey-specific command "svy" using the standard sampling weight (v005/1,000,000), clustering, and stratification. We used simple and multiple logistic regression to determine the main predictors of ARI symptoms. RESULTS ARI symptoms in the previous two weeks in children aged 0-59 months in Cambodia decreased from 19.9% in 2000 to 8.6% in 2005 to 6.4% in 2010, then fewer at 5.5% in 2014; this decrease was statistically significant at a p-value of 0.001. The main factors that increased the likelihood of ARI symptoms were children ages 6-11 months [AOR = 1.91; 95% CI: 1.53-2.38], 12-23 months [AOR = 1.79; 95% CI: 1.46-2.20], and 24-35 months [AOR = 1.41; 95% CI: 1.13-1.76]. Mother cigarette smoker [AOR = 1.61; 95% CI: 1.27-2.05]. And children born into households had non-improved toilets [AOR = 1.20; 95% CI: 0.99-1.46]. However, following factors were found to be associated with decreased odds of having ARI symptoms: Mothers with higher education [AOR = 0.45; 95% CI: 0.21-0.94], Breastfeeding children [AOR = 0.87; 95% CI: 0.77-0.98], and Children born into richest wealth quantile [AOR = 0.73; 95% CI: 0.56-0.95], respectively. Survey years in 2005 [AOR = 0.36; 95% CI: 0.31 - 0.42], 2010 [AOR = 0.27; 95% CI: 0.22 - 0.33], 2014 [AOR = 0.24; 95% CI: 0.19 - 0.30]. CONCLUSION The trends of ARI symptoms among children under five in Cambodia significantly decreased from 2000-2014. Mothers with higher education and smoking; young children ages (6-35 months), and household unimproved toilets facilities are factors that independently increased the likelihood that children would develop ARI symptoms. While breastfeeding children, children born into the wealthiest families, and survey years all reduced the likelihood of an acute respiratory infection. Therefore, government and child family programs must promote maternal education, particularly infant breastfeeding. The government ought to support maternal education and infant breastfeeding in the interest of early childhood care.