Characteristics of Anemia in Children Aged 6 Months to 5 Years Attending a Pediatric Hospital in Lisbon, Portugal

1. Introduction

Anemia is a condition where the number of erythrocytes or red blood cells (RBCs) is insufficient to meet metabolic demands [1]. It is a serious public health problem that affects both rich and poor countries and is associated with impaired development and reduced quality of life [1,2,3,4,5,6,7]. This condition negatively affects cognitive and psychomotor development, impacting school performance and adult productivity through developmental delays and behavioral disturbances [3,7]. Globally, anemia is one of the most widespread nutritional disorders, affecting nearly 40.0% of children aged 6 months to 5 years [3,8,9,10].

The causes of childhood anemia are multifactorial. For example, lack of iron, folate, vitamin B12, and vitamin A can cause nutritional anemia [6,7,10]. Iron deficiency is the most common nutritional deficiency and the primary cause of iron deficiency anemia (IDA) [11]. It often occurs when dietary iron intake is insufficient to meet iron needs, particularly during periods of life when iron requirements are increased, such as during growth and development in pregnancy and infancy [12]. Deficiencies in several other micronutrients (e.g., vitamin A, B12, folic acid, and riboflavin), which are essential for the normal production of red blood cells, likely contribute to the development of anemia [12]. Nutritional and iron deficiency anemia in children impairs immune function, delays mental, physical, and socioemotional development, and increases the risk of death among infants and young children [7,8,10]. Non-nutritional causes of anemia include parasitic infections (e.g., malaria, hookworm, schistosomiasis), as well as blood loss, blood-inherited diseases (e.g., sickle-cell), and infectious diseases (e.g., HIV/AIDS) [7,10]. The interaction mechanism between anemia and infections is complex. Preexisting anemia influences disease susceptibility, while infections can trigger anemia through inflammation, hemolysis, blood loss, nutrient malabsorption, and impaired red blood cell development [13,14]. Parasitic infections are often transmitted through the ingestion of contaminated water or food. While such infections are rarely fatal, they also impair the intestinal absorption of nutrients, causing malnutrition and anemia [15].

Sociodemographic and economic factors, child feeding practices, accessibility to preventive and curative health services, and maternal anemia also play a role in childhood anemia [16,17]. Anemia represents a key indicator of poor health and nutrition, acting as a marker of socioeconomic disparities, as it is inversely linked to household socioeconomic status, particularly in low- and middle-income settings [18]. Children from lower socioeconomic status are often at a higher risk of anemia and its long-term consequences [18]. Poverty, limited access to healthcare services, urban-rural disparities, and caregivers’ education levels are additional factors that may restrict access to nutritious foods, delay timely medical interventions, and negatively influence feeding habits, further increasing the risk of childhood anemia [19]. Few studies [20,21] have shown an association between maternal and fetal anemia, with infants born to anemic mothers often developing anemia a few months after birth. Still, evidence on whether childhood anemia is due to maternal baseline conditions, particularly during pregnancy, is scarce [20,22].

Anemia is defined quantitatively by hemoglobin (Hb), hematocrit, or red blood cell count levels that fall below the normal age- and sex-specific ranges [1]. Anemia in children aged 6 months to 5 years is characterized by low blood hemoglobin and can be classified into the following categories according to severity: mild (10.0 g/dL ≤ Hb ≤ 10.9 g/dL), moderate (7.0 g/dL ≤ Hb ≤ 9.9 g/dL), and severe (Hb < 7.0 g/dL). Additionally, a borderline or pre-anemic stage is identified when 11.0 g/dL ≤ Hb ≤ 11.4 g/dL [6,12,23,24]. Most children with mild anemia have no signs or symptoms, while some may present irritability, jaundice, shortness of breath, or palpitations [25,26]. Moderate and severe anemia has been associated with poor cognitive, emotional, and physical development [27,28]. Severe anemia carries a high 'silent' morbidity and mortality, often occurring months after initial diagnosis and treatment, contributing to under-five child mortality [17].

Other important anemia classifications are based on mean corpuscular volume (MCV) and are categorized into microcytic (MCV < 80fL), normocytic (MCV = 80- 100fL), and macrocytic (MCV > 100fL) [1,29,30]. Microcytic anemia, commonly caused by iron deficiency due to reduced dietary intake, is a leading cause of childhood anemia and is associated with impaired cognitive performance, motor development, and academic performance [31,32,33]. Many pediatric anemias present as normocytic, while macrocytosis is rarely observed in children [1,34]. Normocytic anemia has many causes (e.g., chronic infections and systemic diseases), making its diagnosis more difficult, whereas macrocytic anemia is usually caused by a deficiency of vitamin B12 or folic acid [1,32,35]. Other possible causes of macrocytic anemia include chronic liver disease, hypothyroidism, and myelodysplastic disorders [31,36]. Often, macrocytosis is considered a significant indicator in the diagnosis of bone marrow diseases and acute leukemia in childhood [34].

In 2021, the global anemia prevalence was 24.3% (95% uncertainty interval [UI] 23.9–24.7), corresponding to 1.92 billion people [37]. In the same year, anemia caused 52·0 million years of healthy life lost due to disability (YLDs) [37]. Evidence in the literature shows that the prevalence of anemia in children remains high, with data from 2019 indicating that 40.0% (95.0% uncertainty interval [UI] 36–44) of children aged 6–59 months were anemic, compared to 48.0% in 2000 [38]. The burden of anemia is particularly high in the African region, affecting 60.2 % (95.0% uncertainty interval [UI] 56.6-63.7) of children under five [37,38]. In contrast, Europe has a lower prevalence, affecting 23.0% of children under five in 2011 [39,40].

In Portugal, national anemia prevalence estimates were 4.3 % (95.0% uncertainty interval [UI] 5.7-32.4) in children under five in 2019 [41]. Previous studies [42,43], have shown that anemia is highly prevalent in Portugal and largely undiagnosed. In 2016, a prevalence of 19.9% (95.0% uncertainty interval [UI] 19.0–20.8%) was observed among adults living in mainland Portugal, accounting for 54.2 % of cases in pregnant women and 20.7 % of cases in non-pregnant fertile women [42,43]. Nutritional deficiency anemia (57.7%), particularly iron deficiency anemia (52.7%), represented most of the cases diagnosed [43]. A recent study [40] showed that the prevalence of anemia remains high in mainland Portugal, accounting for 38.2% (95% uncertainty interval [UI] 35.4–41.1) of pregnant women and 51.8% (95.0% uncertainty interval [UI] 50.1–53.4) in non-pregnant fertile women.

While studies on childhood anemia in Portugal have been conducted, few were inherently reviews [44,45]. A 2005 study [46] examining the long-term developmental effects of anemia among infants in Braga, North Portugal, reported an iron deficiency anemia prevalence of 19,7%. Still, much of the available evidence on childhood anemia in Portugal remains scarce or outdated [47]. Given the implications of anemia on childhood cognitive and motor development, school performance, and adult productivity, there is an urgent need for updated research to better characterize children affected by this condition in Portugal.

This study aims to characterize the profile of children aged 6 months to 5 years who were diagnosed with or at risk of anemia, attending external pediatric consultations at the Dona Estefânia Hospital (HDE) in Lisbon, Portugal. The evidence generated in this research will contribute to a better understanding of childhood anemia in Portugal, providing valuable epidemiological insights that can inform targeted healthcare interventions and improve the management of children affected by this condition.

2. Results

2.1. Sociodemographic Characteristics

A total of 222 children, aged 6 months to 5 years, who were referred from the emergency department, primary health care centers, or evacuated from Portuguese-speaking African countries for various conditions, attended external general pediatric consultations between September 2023 and September 2024. Among them, 74 children had anemia or were at risk of developing anemia, and their caregivers were invited to participate. All caregivers agreed to participate, resulting in a 100% acceptance rate (Figure 1). The reasons for consultation are detailed in Supplementary Table 1. Among the 74 children, anemia was the primary reason for consultation in 51 cases (51/74; 69.3%). Other clinical presentations or reasons for consultation (23/74; 31.9%) included bowel failure, abdominal pain, poor weight gain, and others.

Table 1 summarizes the sociodemographic characteristics of children with or at risk of developing anemia. Most participants were male (42/74; 56.8%), aged 2-3 years (29/74; 39.2%), lived in the Metropolitan Lisbon Area (61/74; 82.4%), and were accompanied by their mothers to the consultations (63/74; 85.1%). Most mothers were originally from the Community of Portuguese Language Countries (CPLP) (32/67; 47.8%) and worked in administrative, managerial, or support occupation roles (36/41; 87.8%). Meanwhile, most children’s fathers were from other countries (including CPLP) (34/52; 65.4%) and worked in non-administrative, non-managerial, or non-support occupation roles (22/40; 55.0%).

2.2. Nutritional and Health Characteristics

Our study results indicate that 33.3% (74/222) of children aged 6 months to 5 years who attended external general pediatric consultations were either anemic or at risk of developing anemia. Their nutritional and health characteristics are presented in Table 2. More than half (55/66; 83.3%) of the children had received exclusive breastfeeding. About 65.3 % (47/72) of the children had five or more meals/day, and 82.4% (61/74) had adequate minimum dietary diversity. Regarding their health status, 31.9% (23/72) had been previously hospitalized, and 16.2% (12/72) had a history of food selectivity behavior/refusal of certain types of food (8/12; 66.6%) or vomiting after consuming certain types of food (4/12; 33.3%). Children whose mothers reported vomiting after eating were attending the consultation primarily due to anemia (2/12; 16.7%), abdominal pain (1/12; 8.3%), and Down syndrome (1/12; 8.3%) (Supplementary Table 2).

The overall prevalence of anemia was 94.3% (66/74) based on hemoglobin levels, with 54.5% having mild anemia (36/66), 34.8% moderate anemia (23/66), and 10.6% borderline anemia (7/66). More than half (64/70) of the children had microcytic anemia, while 8.6% (6/70) had normocytic anemia. About 40.0% (12/30) of the children had iron deficiency anemia, and at least 33.3 % (3/9) had sickle cell trait.

2.3. Childhood Anemia by Sociodemographic Characteristics

Our results indicate that anemia cases in children aged 6 months to 5 years, measured by hemoglobin levels, were slightly higher in males (54.5%; 36/66) (Table 3). Similarly, this pattern was observed for cases of microcytic anemia, with 54.7% (35/70) in males. Regarding anemia and its risk by age, the highest proportion of cases was found among children aged 2–3 years (39.4%; 26/66) compared to their peers. Microcytic anemia was also most common in the 2–3 years group (45.3%; 29/70) compared to their peers. Concerning anemia by regional and socioeconomic factors, most cases were in children residing in the Metropolitan Lisbon Area (81.8%; 54/66). Such a pattern was also observed across all anemia classifications. Regarding caregiver characteristics, most anemia cases were observed among children whose caregivers had a basic or secondary level of education (59.1%; 39/66), whose mothers were from CPLP countries (48.3%; 29/60), and whose mothers worked in administrative, managerial, or support roles (91.2%; 31/38). Similarly, children of fathers from non-Portuguese origins accounted for a higher proportion of cases of anemia (66.7%; 30/49) compared to their peers.

2.4. Childhood Anemia by Nutritional and Health Characteristics

Our findings indicate that more than half of the children with or at risk of anemia, as determined by hemoglobin levels, engaged in exclusive breastfeeding (81.4%; 48/59), had received or were receiving complementary feeding (84.8%; 56/66), and consumed cereal porridge (61.5%; 40/65) (Table 4). A similar pattern was observed among children with microcytic anemia, with 87.9% (51/58) receiving exclusive breastfeeding, 89.1% (57/64) having received or currently receiving complementary feeding, and 55.6% (35/63) consuming cereal porridge. Children with low minimum dietary diversity (consumption of 1-3 food groups) had lower rates of anemia, as measured by hemoglobin levels (19.7%; 13/66), than those with adequate dietary diversity (80.3%;53/66). Likewise, more cases of microcytic anemia were also reported among children with low minimum dietary diversity (12.5; 8/64). Supplement intake, after confirmation of anemia diagnosis, during the period of study, was reported in 51.5% (34/66) of anemic children, with iron supplements being the most commonly consumed (61.8%; 21/34). Among children with anemia or at risk, 86.7% (26/30) had an adequate weight-for-age percentile, while 13.3% (4/30) had an inadequate weight-for-age percentile. About 87.1% (27/31) of children with microcytic anemia also had an adequate weight-for-age percentile. A history of food selectivity behavior/refusal to eat certain types of food or vomiting after consuming certain types of food was reported in 16.7% (11/66) of children with anemia (measured by hemoglobin levels). The presence of infection or inflammation was reported in 34.9% (15/43) of anemic cases. About 14.3% (5/35) of children with anemia or at risk had uremia. At least 35.4% (23/66) of anemic children had a history of previous hospitalization, with longer hospital stays (>5 days) being slightly more frequent (53.8%; 7/13) than shorter stays.

3. Discussion

This study characterized the profile of children aged 6 months to 5 years who attended the Dona Estefânia Hospital (HDE) in Lisbon, Portugal, and were diagnosed with or at risk of anemia. Our research focused on a specific subgroup of the pediatric population presenting a particular condition within a specialized sector of the hospital unit. We also observed that a significant portion of the anemic children had a background from the Community of Portuguese Language Countries (CPLP), reflecting the multicultural composition of the hospital's catchment area. Our findings are especially relevant in providing recent evidence on childhood anemia within this specific context in Portugal. Consequently, they cannot be fully generalized to the general pediatric Portuguese population, and some comparisons presented with population-based studies should be interpreted with caution.

Our results showed that the overall prevalence of anemia among children in this age group was 33.3%, indicating that anemia poses a moderate public health issue [48,49]. This prevalence is higher than the national estimates for under-five anemia in Portuguese children (14.3%), the European region (20.3%), and Central and Eastern Europe (22.0%) [38,41]. This prevalence was also slightly higher than those reported by other authors in various regions of Brazil (23.1%) [50] and in Timor-Leste (31.3%) [51]. However, anemia rates were lower than those found in the Community of Portuguese Language Countries (CPLP), namely, in Brazil (38.1% - 56.6%) [52,53,54], in Angola (44.4%) [55], in Cape Verde (51.8%) [56], in São Tomé and Príncipe (83.0%) [57], in Equatorial Guinea (85.0%) [58], and in Mozambique (62.2% - 83.0%) [59,60,61]. Our findings are also slightly higher than those reported for the Portuguese adult population residing in mainland Portugal (19.9%) [42].

We observed that rates of moderate (MO) and mild (MI) anemia were 54.5% and 34.8%, respectively, higher than the national estimates for Central and Eastern Europe (6.0% for moderate and 16.0% for mild anemia) [38]. These rates were also higher than those reported in studies conducted in Northwest Ethiopia (MO: 42.3% and MI: 23.7%) [62], in Western Peru (MO: 32.7% and MI: 10.9%) [63], in Southwest Ethiopia (MO: 15.8% and MI: 25.0%) [64], in Tanzania (MO: 44.8% and MI: 9.1%) [65]. Microcytic anemia rates were high (91.4%), with 74.0% of children having an iron deficiency (ID), 40.0% having iron deficiency anemia (IDA), and 33.3% having the sickle cell trait (SCT). The rates of iron deficiency and iron deficiency anemia observed in our study are higher than those reported in a previous study [47] conducted in the Cascais Municipality of the Metropolitan Lisbon Area among children aged 6 to 24 months (15.8% and 5.0%, respectively). We found higher rates of ID and IDA than those reported in Brazil (ID: 35.8%) [66], in Thessaloniki-Northern Greece (ID: 14.0% and IDA: 2.9%) [67], in Almería-Spain (ID: 8.7% and IDA: 2.0%) [68], in Thessalia- Central Greece (IDA: 7.9%) [69] and in Western Europe (ID:11.8%) [70].

The high rates of anemia reported in our study should be interpreted in the light of its unique sociodemographic characteristics. As such, these rates might be partly explained by the considerable portion of children who have a background from the Community of Portuguese Language Countries (CPLP) and African regions, where anemia and hemoglobinopathies are more prevalent [71]. Additionally, as stated in previous studies, these variations in anemia prevalence might also be attributed to a combination of geographical disparities (e.g. differences in climate), cultural factors (e.g. food practices), nutritional factors (e.g. dietary habits and food intake), genetic factors (e.g. inherited blood disorders), and socioeconomic context (e.g. caregivers' education level and access to health facilities) [17,44,70,72,73].

Sociodemographic patterns in childhood anemia

Our results indicate that anemia rates were higher in male children, aged 2-3 years, and among those with caregivers who had a basic or secondary level of education. Consistent with our findings, several studies [17,74,75,76] have demonstrated that boys are generally more susceptible to anemia than their peers. This may be attributed to increased prenatal and post-natal growth in males, which elevates their micronutrient needs, often not fulfilled through diet alone [74,76].

Our results align with previous studies in Brazil [66] and India (Raju et al., 2024). Nevertheless, our findings differ from studies conducted in northern Tanzania [77], Ethiopia [78] and Eastern Burkina Faso [2], which reported higher anemia rates among children aged 6-23 months compared to their peers. This discrepancy may be explained by differences in disease burden, cultural and dietary practices, and maternal nutrition between Portugal and these countries [17,37,42,70,72,73].

Similar to previous studies [77,79,80], higher anemia rates were observed among children whose caregivers had a lower level of education. Our study also showed higher rates of anemia among children whose mothers are from the Community of Portuguese Language Countries (CPLP) and fathers of non-Portuguese origins. Few studies [44] were conducted to analyze anemia in Portugal and other CPLP countries, showing that anemia plays a relevant role in disability and life imbalances in pregnant women and children under five years of age in Mozambique compared with Portugal. In addition, some authors [81] argue that, in past years, sickle cell trait disease in Portugal has been aggravated by immigrants from Angola and São Tomé and Príncipe. Other authors [82] state that immigrant mothers often may carry pre-existing conditions common in their countries of origin (e.g., anemia and hemoglobinopathies) that are less frequent in host countries like Portugal, and these women often request and receive less health care during and after pregnancy. A recent study [71] conducted in the municipalities of Amadora and Sintra, in the Lisbon Metropolitan Area, also reported high rates of anemia (30.1%; 65/216) and iron deficiency anemia (27.7%; 18/65) among migrant children and adolescents (aged between 1 and 16 years). The same study [71] emphasized the need to include systematic screening for sickle cell disease among the migrant population from African countries, where haemoglobinopathies are common, due to the importance of the disease in the Portuguese population. Broader socioeconomic strategies [83], nutrition education for caregivers [78], and strengthening the training and education of healthcare providers in the area of multiculturalism [82] could be crucial for mitigating childhood anemia in this setting. Nationwide strategies for the prevention and management of anemia in Portugal, which integrate nutrition education, particularly for pregnant women and caregivers of young children [42,43] may play a vital role in the prevention of childhood anemia. More research on socioeconomic disparities and childhood anemia is needed to better guide future strategies for mitigating this condition in this setting.

Nutritional patterns and health-related characteristics in childhood anemia

In this study, we observed that exclusive breastfeeding and complementary feeding rates were high among children with anemia. Meal frequency (consumption of five or more food groups per day) and adequate dietary diversity (consumption of four or more food groups) were also higher in children with anemia. These results contrast with several studies [80,84,85]. An explanation for this discrepancy may be linked to the nutritional quality of children's diets, particularly a low intake of key micronutrients such as iron, folate, and vitamin A, or the limited bioavailability of iron due to poor absorption [84].

Our findings show that some children with anemia also exhibit uremia. As noted by several authors [80,86], comorbidities (such as metabolic dysfunctions and infections) may play a crucial role in childhood anemia. On the other hand, anemia-related impairment may worsen the management of children with coexisting comorbidities, negatively impacting their quality of life [87]. Thus, more research (e.g., analytical cross-sectional or longitudinal studies) is needed to assess not only feeding practices and dietary habits in this age group but also the cultural, socioeconomic, and metabolic factors that might influence childhood anemia in this setting.

4. Materials and Methods

Study setting

Portugal, officially the Portuguese Republic, is the westernmost country of mainland Europe, located in the Iberian Peninsula and occupying a total area of 92,211.9 km2 [88,89]. It is bordered to the north and east by Spain, and its western and southern coastline is surrounded by the Atlantic Ocean. Portugal’s territory also includes two autonomous regions, the archipelagos of the Azores and Madeira, located in the Atlantic Ocean [88,89,90]. Portugal has the 12th-largest population in the European Union, with 10.6 million inhabitants [88,90]. Lisbon is the capital of Portugal, the largest Portuguese municipality (with over 550,000 inhabitants), and, along with 17 other municipalities, forms the Lisbon Metropolitan Area (which has around 3 million inhabitants) [90]. This study was conducted at the External Consultations of the Pediatrics Medical Service of Dona Estefânia Hospital (HDE)—Unidade Local de Saúde de São José (ULS São José) in Lisbon. Dona Estefânia Hospital is a reference unit in pediatrics for Southern Portugal and the archipelagos of the Azores and Madeira. It specializes in maternal and child health care [91]. The external consultations are conducted in a building with two sections: one dedicated to medical specialties and the other to surgical specialties. Within the medical specialties, consultations are offered in nine areas: general pediatrics, pulmonology, cystic fibrosis, sleep pathology, infectious diseases, travel medicine, rheumatology, nephrology, and chronic renal failure [92]. In addition, other specialized consultations are included, such as the Acute Patient Reassessment Consultation (CORDA), adolescent pediatrics, cooperation, palliative care, the Pre-Immunosuppressive Treatment Infectious Screening Consultation (CRIIPTO), and the Pediatric Risk Support Consultation (CARPE), as well as the Acute Diseases Consultation. In 2024, Dona Estefânia Hospital recorded a total of 59,870 pediatric medical consultations across all medical specialties. Of these, 4,169 were general pediatrics consultations, with 1,046 corresponding to first consultations and 2,420 to subsequent consultations (follow-up appointments), covering a total of 2,301 patients [92].

Study design, population, and sample universe

This hospital-based, cross-sectional descriptive study was conducted from September 2023 to September 2024. The sample universe was the External General Pediatrics Consultation section (area) of the Dona Estefânia Hospital. All children aged 6 months to 5 years old who attended the external general pediatric consultations during the study period were included (census-based approach).

Inclusion and Exclusion Criteria

The inclusion criteria were children aged between 6 months and 5 years, diagnosed with or at risk of anemia, who attended the External General Pediatrics Consultation section (area) at Dona Estefânia Hospital. This included: children referred from the emergency department for evaluation or follow-up by a pediatrician; children referred by family doctors from Health Centers; and children evacuated from Portuguese-speaking African countries due to various pathologies.

The exclusion criteria were children younger than 6 months, children aged 6 years or older, and children without available hemoglobin or hematocrit measurements. Also excluded were children followed in hematology or other specialized consultations.

Data collection and quality control

The total number of children aged 6 months to 5 years, both with and without anemia, who attended external pediatric consultations during the study period was obtained from daily consultation records. Children diagnosed with anemia or those identified as at risk were selected during each consultation. The study was then explained to the children’s caregivers, and their written informed consent was obtained. A pretested questionnaire, consisting of three sections on sociodemographic characteristics, feeding habits, and health status, was used to collect information. Clinical data were obtained from electronic medical records and children’s health cards. Investigators carefully monitored data collection. To ensure data quality, double data entry verification was conducted, and the information from paper-based forms and electronic questionnaires was compared. Data cleaning was performed to verify frequencies, consistency, and missing values, and any errors identified were corrected.

Outcome variable

The outcome variable for this study was the presence of anemia or the risk of developing anemia in children aged 6 months to 5 years. In the context of this study, anemia and the risk of developing anemia were defined as 11.0 g/dL ≤ Hb ≤ 11.4 g/dL. We used the following hemoglobin (Hb) cut-off values to classify anemia in children aged 6 months to 5 years: not anemic (Hb > 11.4 g/dL), borderline or pre-anemic stage (11.0 g/dL ≤ Hb ≤ 11.4 g/dL), mild (10.0 g/dL ≤ Hb ≤ 10.9 g/dL), moderate (7.0 g/dL ≤ Hb ≤ 9.9 g/dL), and severe (Hb < 7.0 g/dL) anemia [6,12,23,24]. Other anemia definitions used in this study were: anemia based on hematocrit levels [not anemic (hematocrit = 34.0%-40.0%) and anemic (hematocrit<33.0%)] and red blood cell size, measured by the mean corpuscular volume (MCV) [microcytic (<80 fL), normocytic (80-100 fL) and macrocytic (>100fL)] [29,93]. More details on definitions of anemia and the outcome variable can be found in the Supplementary file Table 3.

Exposure variables

In this study, exposure variables included sociodemographic characteristics (sex, age, residence area, caregiver’s degree of kinship, caregiver’s education level, country of origin, and parental occupation) and nutritional characteristics (history of breastfeeding, complementary feeding, cereal porridge intake, number of meals/day, intake of various food groups: cereals and derivatives, tubers, meat, fish and eggs, dairy products, fruits, legumes, vegetables, fats, and oils). Minimum dietary diversity was classified as "adequate" if children consumed four or more food groups, and "inadequate" if children consumed less than four food groups. Other exposure variables included anthropometric characteristics (weight percentiles) and health characteristics (vomiting or refusal to eat, presence of infections or inflammatory conditions, glucose and bilirubin levels, uremia, hospitalization, and duration of hospitalization). More details on exposure variables can be found in Supplementary file Table 3.

Data analysis

Data were analyzed using SPSS 28.0 software (International Business Machine Corporation [IBM Corp]) [95]. Descriptive statistics, including frequency distributions and cross-tabulations, were performed to summarize the characteristics of study participants and key variables.

5. Conclusions

This study describes anemia among children aged 6 months to 5 years attending external general pediatric consultations in Portugal. Our findings indicate that childhood anemia poses a moderate public health issue in this setting. Anemia rates were higher among male children, those aged 2-3 years, those whose caregivers had a low level of education, and those whose mothers were from the Community of Portuguese Language Countries (CPLP). Further research, including analytical cross-sectional or longitudinal studies, is necessary to better understand the role of feeding practices, dietary habits, nutritional adequacy, and other potential influencing determinants, such as cultural, socioeconomic, and metabolic factors, in childhood anemia in this setting.

6. Strengths and Limitations

To our knowledge, this is the first hospital-based study in Lisbon to characterize children aged 6 months to 5 years who are diagnosed with or at risk of anemia. Given the limited existing research on this issue in Portugal, our study can serve as a baseline for future research (whether analytical cross-sectional or longitudinal) focused on the role of feeding practices, dietary habits, nutritional adequacy, and other potential influencing determinants, such as cultural, socioeconomic, and metabolic aspects, on childhood anemia in Portugal. In addition, by providing valuable evidence, our study establishes a foundation for improving the prevention, management, and care of anemia in children living in Portugal.

However, there are some limitations to our study. First, due to constraints from the COVID-19 pandemic, which placed significant pressure on the National Health Service (SNS) and pediatric care in Portugal, the data collection process was impacted. Consequently, this study adopted a purely descriptive design. Our one-year study focused on characterizing the profiles of children diagnosed with or at risk of anemia and did not include children without anemia, limiting the analysis of relationships or associations between various determinants and childhood anemia. Second, our sample universe was not randomly selected, as it consisted of all children aged 6 months to 5 years old who attended the external general pediatric consultations section of Dona Estefânia Hospital and were chosen based on availability during the study period. As such, our findings should not be generalized to all pediatric consultations or patient profiles at the hospital. Third, the sociodemographic composition of our sample, which includes a substantial proportion of anemic children with backgrounds from the Community of Portuguese Language Countries (CPLP), may contribute to the high rates of anemia observed in this study and further limit the generalizability of our findings to the broader Portuguese pediatric population. Therefore, more comprehensive studies are needed to explore anemia associations with various determinants, provide more generalizable results, and enhance our understanding of the factors influencing anemia in children in Portugal.