The evidence here presented suggests inequalities in the occurrence of health problems, mainly related to the accumulation of morbidities in the first year of life. We observed absolute and relative inequalities for both ages (12 and 24 months). In addition, the average number of health problems was higher among children whose mothers had less education and belonged to lower-income families, with a dose-response relationship.
The observed inequalities confirm the body of evidence on the influence of social determinants on the health situation of populations. Identifying a greater occurrence of health problems among children belonging to family groups with lower purchasing power is in line with the findings on the long-term effect of socioeconomic inequalities in the higher occurrence of chronic diseases in adulthood (16). In addition to other factors throughout the life cycle, such as healthy habits and obesity, the greater burden of acute problems in childhood may be associated with the chance of a chronic low-grade inflammation in adulthood, indicating another possible causal path for the cumulative effect of socioeconomic position on the pathophysiology of chronic diseases and mortality risk (3, 17–19).
The observed inequalities are related to the living conditions of families who experience difficulties providing adequate care and protection for health problems (20), mainly respiratory ones. Pelotas-RS is a city with high levels of humidity and severe winter, which makes quality housing, public transport, education system, and access to goods and services even more necessary, ensuring, as much as possible, the protection of children from breathing problems. On the other hand, a factor that may attenuate these inequalities is the protection generated by exclusive breastfeeding, which is greater among children with lower purchasing power (55% vs. 28% and 57% vs. 34%, compared to the extremes of education and income quintiles, respectively). Even so, this possible protection does not seem to be sufficient to mitigate the differences between children from different socioeconomic positions.
In addition, children up to 12 months of age may have a lower immune response when compared to those aged two years, that is, they may be more susceptible to health problems. In this study, lower maternal education and lower income were statistically associated with two or more health problems among children aged 12 months. Not only a lower immune response but also socio-economic conditions may influence child health. Studies have identified that children from families with lower socio-economic status, less education, or even brown or black skin color presented a higher risk of unfavorable health conditions (21, 22).
Hospitalization and pneumonia were health conditions whose prevalence drew our attention, especially among 12-month-old children. However, other problems such as coughing and difficulty breathing, which are part of the diagnosis for asthma, were also alarming for both 12-month and 24-month-old children. Regarding hospitalization, a study carried out in the 2004 cohort of Pelotas/RS observed similar prevalence to those identified in the present study. This prevalence was reduced at four and six years of age (9). Pneumonia is a major cause of hospitalization among children (9, 23, 24), and in some more severe cases, it can progress to death, especially among children under 12 months of age (23, 25). However, after vaccination against the main causative agents of the disease (12 months), the prevalence of pneumonia decreased considerably, remaining stable or without a notable reduction among children from families with lower purchasing power (26).
We are aware that our study may have some limitations. The possibility of a recall bias due to the temporality of the questions should be considered, which could underestimate our findings. However, we believe that all health problems investigated are very marked at this stage of life (children up to two years old). Another limitation could be the use of cough and difficulty breathing in the score for health problems together with pneumonia and hospitalization, considering that these two problems are part of the diagnosis of asthma. Nevertheless, the association was maintained when we performed sensitivity analyzes removing cough and difficulty breathing from the health problem score. Finally, we obtained all health problems through a report by the mother or guardian, and we did not perform objective measures (medical records, for example) to assess these health problems among the children.