“Daycare Syndrome”: Do Recurrent Infections in Infants and Preschoolers in Daycare Play a Role in Immune System Development?
Do common infections acquired in daycare benefit young immune systems or put children at risk?
“Daycare syndrome” may not qualify for an official listing under common childhood ailments, but parents, daycare providers and physicians alike are familiar with the increased risk of exposure to common infectious diseases and the recurring cycles of illness in infants and preschoolers that are associated with daycare attendance.
Do these recurring cycles of illness contribute to the development of a healthy immune system – or detract from the child’s long-term health? And are there ways to help support the child’s immune system that will better prepare them for a healthy life in daycare?
Building the child’s immune system
Our immune system helps protect us from pathogens with its multiple layers of varying purpose and specificity. The immune system becomes “educated” as we are gradually exposed to the environment. One branch of the immune system, which is highly adaptive, involves antibodies called “immunoglobulins”. Immunoglobulins are divided into five classes – IgM, IgG, IgA, IgE and IgD – each of which has evolved to deal with different antigens. The capacity of the body to produce each of these varies with age.
- Passive immunity refers to antibodies present in breastmilk that provide the infant with temporary immunity to diseases to which the mother has been exposed. This can help protect the infant against infection during the early months of childhood. Maternal IgG gradually disappears during the first 6 to 8 months of life, as the rate of the infant’s IgG synthesis increases. Adult concentrations of total IgG are reached by about 7 to 8 years of age.
- Adaptive immunity develops throughout life as the result of exposure to pathogens and through immune response to vaccinations. Newborns begin to synthesize IgM antibodies very soon after birth in response to their environment. The premature infant appears to be as capable of doing this as the full-term infant. At about 6 days after birth, the serum concentration of IgM rises sharply and continues to rise until adult levels are reached by approximately 1 year of age.
Exposure to common infectious pathogens thus has an important function in building the child’s healthy immune system via adaptive immunity. A variety of infectious agents, both viral and bacterial, are commonly encountered by children in daycare, resulting in a range of illnesses including upper and lower respiratory tract infections, acute otitis media, gastrointestinal illness, and certain skin ailments. The young child first entering daycare – especially a child with no older siblings – essentially encounters an assault on the immune system that is a direct result of increased environmental exposure. Children under 1 year of age may be particularly hard hit as they are still in the early stages of immune system development. Parents will often cite their frustrations with the on-again, off-again illnesses experienced by their child. Parents and siblings are often co-infected, further exacerbating the family’s frustrations with the cycles of illness and recovery that interfere with home, work, school and social routines.1
Formal daycare centers will typically have policies in place to ensure that all children have received required age-appropriate immunizations for major communicable diseases. Thus, it is the more common infectious illnesses for which vaccines do not exist that comprise “daycare syndrome”. The optional varicella vaccine, introduced in the U.S. in 1995, is still not in widespread use, so chicken pox still retains a place on the list of routine infections of childhood.2
Increased risk for infections
Studies confirm that daycare attendance does increase the risk of contracting infectious diseases. In a study of risk factors for invasive pneumococcal disease (a major cause of pneumonia) among children in the United States, attendance at a group daycare center during the preceding 3 months was associated with an approximately 2.3-fold increase in invasive disease among children aged 12-23 months, and a 3.2-fold increased risk among children aged 24-59 months. In studies of acute otitis media (AOM, middle ear infections) resulting from all causes, risk was higher among children who attended daycare outside the home. A younger age when starting daycare also increased risk for experiencing recurrent AOM. Daycare attendance is likewise a risk factor for other acute upper respiratory tract infections among children aged <5 years.3,4
A population-based study of Danish children between 1989 and 2004 found that hospitalizations for acute respiratory infections in children attending daycare declined with age, with the highest incidence in children under 1 year of age (34%) followed by ages 1 to 2 years (28%), and declining numbers thereafter. The incidence rate ratios for risk of hospitalization were higher for children under the age of 3; for children enrolled in daycare for less than 12 months; and for children with no siblings.5
Asthma and atopy: Does daycare attendance increase risk?
In recent years, investigators have discovered that illness can result when the immune system – through overly hygienic practices – is not allowed to engage in natural immune-building battles against bacteria and viruses. The “hygiene hypothesis” arose as an explanation for the rising prevalence of asthma and allergies in many developed countries.6
The reported impact of daycare attendance on respiratory and atopic symptoms varies between studies. One study concluded that attending daycare was associated with increased risk of symptoms related to respiratory tract infections, eczema and allergic reactions to food. No sign of protection from allergic diseases provided by daycare attendance was found up to 6 years of age. Multiple airway infections and daycare attendance were found to be independently associated with asthma and allergic symptoms.7
Another study found that children with no siblings who were exposed to a daycare situation before the age of 1 year were less likely to develop allergies than those who entered at an older age. For children from larger families, older siblings seemed to have provided the same exposure that daycare would have done.8
Yet another study suggested that in children with a parental history of allergy, the protective effect of daycare attendance in the first year of life against development of allergy had begun by 2 years of age, but a protective effect against asthma may not be evident until after age 4.9
Following the principles of the hygiene hypothesis, it could be concluded that encountering a range of pathogens and allergens through daycare attendance would lead to less sensitization later in life. However, the question still remains whether daycare attendance and subsequent exposure to more frequent early infections is a risk for, or a protection against, future atopy or asthma.
Treatment and Prevention Strategies
Many primary care physicians would likely concur that daycare-acquired respiratory tract infections are some of the most common ailments in the under-5 age group. In light of the issues of bacterial antibiotic resistance and inappropriate use of antibiotics, healthcare professionals today are focusing on disease prevention. Determining whether recurrent infections are due to increased environmental exposure or to an immunological concern with the child is crucial to next steps in the course of action.
For illnesses related to environmental exposure, easy preventive strategies include:
- good hygiene practices for children and daycare staff
- consistent and thorough infection control practices, notably handwashing
- respiratory etiquette (good health manners and practices) for children who attend daycare with respiratory tract infections.
Other methods of providing support for young children’s developing immune systems are currently being explored. The use of probiotics is receiving notable attention in recent years in this capacity. Studies have been conducted specifically within the daycare population on the results of consuming probiotic-supplemented foods.10,11
Daycare-acquired common infections pose an undeniable burden on children and their families. Even though escalated exposure to pathogens in daycare can contribute to building the child’s immune system, recurring cycles of illness are difficult to deal with for children and their families. Further research is indicated into approaches to help support healthy, robust immune systems in children attending daycare; current progress with probiotic-supplemented foods is promising.