This was the first study aimed to determine the prevalence of CAS, and its multilevel associated factors, among infants and young children in Ethiopia. The work provided evidence that there was a high level of anemia and stunting co-occurrence in Ethiopia, with almost a quarter of the children affected. We found CAS linked to various multiple-level influences. The distal factors associated with higher odds of CAS were living in rural areas, low household wealth, and low caregivers’ educational level. The proximal factors found associated with higher odds of CAS were male sex, age above 12 months, small birth size, no vitamin A supplement use, no consumption of vitamin A rich food items, meat and legumes, and low meal frequency.
We found a concerning high level of anemia, with only less than a third of the children being not anemic. The finding was, however, consistent with the recent national DHS report which showed 72 and 56% anemia prevalence among under-2 and under-5 children, respectively . Stunting was also highly prevalent, though not as high as anemia. The same finding was reported in previous studies, which showed a two-fifth prevalence of stunting among under-5 Ethiopian children [1, 13, 23]. We found that almost a quarter of the children were concurrently anemic and stunted. There was no previous report on the magnitude of CAS, and factors associated with it, in Ethiopia as well as other African countries, limiting the comparison of our findings. However, our finding was within the range of reports from Asian and Latin American countries. Albalak et al.  reported a 15.2% CAS prevalence in Honduras. Castejon et al.  reported a 5.9% CAS prevalence in Venezuela. CAS prevalence was 21.5% in India and 30.4% in Peru .
We found various factors linked to CAS. Children of low household wealth or caregivers of low education level were more likely to be concurrently anemic and stunted. These findings could be easily acknowledged because child health-enhancing behaviors, like proper feeding, hygiene, and utilization of health services, are often sub-optimally practiced among communities of low wealth and educational status [8, 11, 24]. We also found a more clustering of CAS in those above 12 months of age. This could be due to the nature of stunting that it takes more time to manifest than anemia which takes a shorter time. The existing literature shows that most stunting occurs more during the period 12 to 23 months of age [11, 25]. In general, children under-2 years of age bear a higher burden of both anemia and stunting, particularly in developing countries [4, 9, 12]. Our finding of higher odds of CAS in boys than in girls was in agreement with previous reports which consistently demonstrated higher risks of anemia and stunting in boys [10, 25, 26]. Small birth size was associated with a significantly higher odds of CAS. This finding was also consistent with the existing literature which shows low birthweight linked to various poor health and nutritional outcomes [25, 26].
Vitamin A intake, in dietary as well as supplement form, was associated with a significantly lower CAS prevalence. This would be most likely due to the role of vitamin A in promoting optimal hematologic and linear growth status [24, 27,28,29]. Vitamin A also boosts humoral as well as cell-mediated immunity, thereby reducing the risk of anemia due to infection . Vitamin A also plays an important role in promoting child growth, thereby reducing the risk of stunting [27, 28, 30]. Thus, it could be easily acknowledged that a vitamin A deficient child would be at a higher risk of being concurrently affected by anemia and stunting. Lack of meat and legumes consumption, as well as low meal frequency, were independently associated with higher odds of CAS. This could be due to the better amino acid and iron profiles in meat and legumes [31, 32]. Thus, suboptimal intake of legume or meat products might be expected to negatively impact both hemoglobin and growth statuses [23, 31].
Among the dietary factors, milk consumption was not significantly linked to CAS. This could be, in part, because most of the study participants were of less educated caregivers and from rural areas, where animal milk is consumed mainly raw. Previous reports showed opposing effects of raw animal milk on height and hemoglobin statuses [33, 34]. It promotes height gain, thus reduces the risk of stunting [34, 35], but predisposes to gastroenteritis and occult bleeding, thus increases the risk of anemia [33, 36]. Iron supplement use also did not demonstrate a significant link to CAS, though it would be expected to promote both hemoglobin and height . Our finding could be likely due to factors like: a) the children taking iron supplement might be the already anemic ones, b) we did not account for dose, frequency, and adherence to the iron supplement use, or c) the sample lacked the power to detect the association, if any, because the number of children who took iron supplement was low. Notwithstanding the role of iron in red blood cells formation and body growth, previous randomized control and meta-analysis studies also reported as iron supplement use lacked a demonstrable effect on physical growth as well as hemoglobin level of children [37, 38].
The findings of this study have important policy and research implications. The high level of CAS was concerning given each of the two conditions are of significant consequences and their co-occurrence would be more threating to the health of children. It is also important to note the criticality of the first 1000 days of life, during which the body is more vulnerable to both nutritional and non-nutritional threats [4, 11]. Thus, the finding might be an indicator of the need to report on CAS and also investigate whether these children are being reached with a priority through the existing health/nutrition programs. Currently, there is confusion on how to address the various forms of malnutrition. To address stunting and anemia, WHO guidelines recommend a comprehensive and integrated approach, as it also has multiple benefits [12, 24]. Some authors, however, questioned the approach arguing that anemia and stunting are independent of each other and better be addressed by tailored interventions [15,16,17]. We are of the WHO recommendation as anemia and stunting share most of their risk factors. Thus, we recommend strengthening the existing public health and nutrition efforts, including improving infant and young child feeding practices, micronutrient supplementation, hygiene, and health care.
The main strengths of this study were it was based on a nationally representative data and took into account the multi-factorial nature of CAS, by incorporating not only the immediate dietary factors but also the non-dietary factors with the potential to influence CAS. Our analysis approach, hierarchical regression, took into account the interrelationships among the various explanatory variables and enabled building models according to the level of the variable influence. One of the main limitations of the study was that a cause-effect relationship could not be inferred as it was based on cross-sectional data. The collection of data on some variables, like birth size, infection history, dietary frequency, and diversity, based on the subjective memory of the caregiver might have introduced recall bias and miss-classification.