This study was done in 45 low- and middle-income countries that had the most recent DHS data from 2015 to 2024, aiming to assess the pooled prevalence of comorbidity in diarrhea and ARI. Accordingly, the study revealed that the pooled prevalence of comorbidity, diarrhea, and ARI in low- and middle-income countries was 5.44%, 12.57%, and 22.25%, respectively. The co-occurrence of diarrhea and ARI poses amplified public health challenges, increasing morbidity rates and complicating treatment efficacy. This comorbidity also heightens clinical risks, such as dehydration, impaired respiratory function, and an increased likelihood of mortality due to compromised immune responses. This study highlights the need for integrated healthcare strategies. As a result, public health programmers could prioritize inter-sectorial and multi-country interventions like improved hygienic practices and quality air. Furthermore, resource allocation should be prioritized by policymakers toward regions exhibiting the highest burden of comorbidity of diarrhea and ARI.
According to the multi-level, multi-variable analysis, male children had a higher chance of comorbidity of diarrhea and ARI. This finding is supported by other studies done across the globe27,28,29,30. A plausible explanation could be the mother’s preference for revealing a compliant of male child31. As a result, they are able to notice changes in the health status of male children early and report to the healthcare provider accordingly. In addition, boys had a higher chance of exploratory behavior32, such as taking risks like playing in unsanitary environments, which increased their exposure to pathogens causing diarrhea and ARI.
Our finding confirmed that comorbidity of diarrhea and ARI is more common in children less than 2 years. This is in line with many prior studies33,34. This is due to the fact that younger children’s immunity is less developed, making them at increasing risk of infection35. In addition, children in this age depend on mothers; as a result, any unhygienic feeding exposes children to infection.
We found a significant association between the wealth status of the household and the comorbidity of diarrhea and ARI. This is in line with the study done in Bangladesh and Nepal36,37. The possible justification could be poor households have unmet nutritional needs and adopt inappropriate feeding practices that exacerbate the risk of infection37. In addition, poorer households had limited access to health care services due to out-of-pocket money that led them to delayed and inadequate care during their illness.
This study found that children born to mothers aged over 35 years exhibited a lower likelihood of developing comorbidity of diarrhea and acute respiratory tract infection, while those born to mothers younger than 20 years were at a higher chance of comorbidity, relative to the reference group of mothers aged 20–34 years. These findings are consistent with evidence reported in previous studies8,9,38. This might be due to older mothers having better experience in accessing healthcare, more stable socio-economic conditions, and greater awareness of child health needs; as a result, the child will have a lower risk for diarrhea and ARI. On the other hand, teenage mothers might have limited skill and knowledge in child care, poor access to health care due to financial constraints, and low-level education, which contributes to the comorbidity of diarrhea and ARI.
This study found a significant association between household access to mass media and lower odds of comorbidity of diarrhea and ARI. This is supported by other studies39,40. This is due to the fact that mass media, especially radio and television broadcasts, help to spread awareness and reach distant places40. Through these channels, health information can be disseminated in the local language, and that larger population and community will acquire health information. Having access to this kind of information will enable parents of under-five children to seek the right medical attention, which will ultimately encourage health-seeking habits.
According to this study finding, children who have not received a vaccination had a higher chance of being exposed to comorbidity than children who have received a vaccination. This is congruent with other studies41,42. This is due to the fact that vaccination helps children develop immunity against infection, such as the pneumococcal vaccine, which lowers the risk of respiratory infection, and the rotavirus infection, which protects children from diarrheal disease. Therefore, strengthening vaccination programs is crucial to lessen diarrhea and ARI.
According to this study finding, children from households without health insurance had a higher chance of comorbidity as compared to children from non-insured households. This is congruent with other studies43,44. This is due to the fact that children from uninsured households had many barriers, including delayed care, timely medical management, unmet medical needs, and higher out-of-pocket costs. On the other hand, insured children often had better access to preventative care, timely medical management, and health education. As a result, the governments in the respective countries should take all responsibilities to strengthen health insurance coverage for the people.
Children residing in rural areas demonstrated a higher chance of experiencing comorbidity of diarrhea and acute respiratory tract infection compared to their urban counterparts. This is in line with other studies45. This discrepancy could be due to contextual factors between urban and rural areas. For instance, in rural areas, there is a lack of access to clean water and sanitary facilities, and the use of solid fuel might be increased46. In addition, rural communities lack sufficient health facilities with lesser quality that result in incomplete infectious disease control.
Both small-weight- and large-weight-born children had higher chance of comorbidity of diarrhea and ARI as compared to children born with average weight. This is supported by a study in Brazil and Mozambique47,48. This is due to the fact that low-birth-weight children have lower immunity levels and underdeveloped organs, predisposing them to infection49. Conversely, a high birth weight may be associated with increased risk of delivery complications and potential metabolic disorders.
Countries that reported the DHS survey between 2020 and 2024 exhibited lower chance of comorbidity of diarrhea and acute respiratory tract infection among children compared to those that reported DHS data between 2015 and 2020. This observation is consistent with findings from previous research50. This might be due to improved public health intervention in many countries through WASH (Water, sanitation and hygiene) program, expanded vaccination program and integrated management of childhood illness46,51.
Children who had clean cooking source had lower chance of comorbidity of diarrhea and ARI as compared to children with solid cooking source. Children living in households that use clean cooking fuels (such as electricity, LPG, or biogas) had significantly lower levels of indoor air pollution compared to those using solid fuels (like wood, charcoal, or dung). Solid fuel combustion releases harmful pollutants such as particulate matter (PM₂.₅), carbon monoxide, and volatile organic compounds, which impair respiratory health and increase susceptibility to infections52,53. Moreover, indoor air pollution weakens mucosal immunity, making children more vulnerable to both acute respiratory infections (ARI) and diarrheal diseases, especially in poorly ventilated homes. Clean cooking reduces this exposure, thereby lowering the odds of comorbidity.
Children residing in South and Southeast Asia, Central Asia, Oceania, and sub-Saharan Africa had higher odds of comorbidity of diarrhea and ARI as compared to children residing in Europe, Latin America, and the Caribbean54. This could be due to higher burden regions like Asia and Africa, limited access to health care, poor sanitation, inadequate nutrition, and higher prevalence of infectious disease. In contrast, Europe, Latin America, and the Caribbean have a better health infrastructure, a higher standard of living, and more effective public health interventions, which reduce the risk of such morbidity.
As compared to children residing in upper middle-income countries, children residing in lower and lower middle-income countries had a higher odd of comorbidity of diarrhea and ARI. This is supported by other studies. This might be due to limited access to health care, poor sanitation, and malnutrition that leads to high exposure to infectious disease.
Strength and limitation
The strength of this study stemmed from its focus on several nations with varying geographic and economic backgrounds that may help programmers and policymakers to create effective multi-country initiatives. The cross-sectional study design made it impossible for the study’s findings to establish a causal link between the independent variables and the outcome. In addition, due to the DHS nature of the data, important proximal predictors like recent infection in the household, immune status of the child, and crowding may result in under/overestimation of the comorbidity of diarrhea and ARI. Therefore, we recommend future researchers conduct studies by incorporating proximal factors associated with ARI and diarrhea.