Early childhood infections may boost risk of illness in later life

The research adds to growing evidence that the viruses and bacteria children are exposed to during their first few years of life may alter how they respond to other infections as they get older. Previous research has linked frequent infections during infancy to a greater risk of cardiometabolic disease, mental illness and atopic diseases such as eczema, asthma and hay fever in later life. However, it has been difficult to disentangle this from children’s environment and social circumstances, which may also contribute to their disease risk.

To better understand these effects, comprehensive longitudinal studies – which repeatedly observe the same group of people over time – are needed, alongside detailed information on relevant exposures during the same period, said Dr Nicklas Brustad at the University of Copenhagen in Denmark, who led the new study.

“A high infection load in the first years of life may increase the risk of infections in later childhood and a range of other chronic disorders later in life […] This knowledge may provide the basis for targeted and more focused disease prevention in specific children.”

– Dr Nicklas Brustad et al

Infection diaries

To aid these efforts, the researchers turned to data from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) 2010 cohort – a group of 736 healthy women who were recruited between 2008 and 2010 when they were pregnant, and whose children’s health has been tracked since birth. This included keeping daily diaries of children’s symptoms, any medication they were taking, and any doctor-diagnosed episodes of tonsillitis, middle ear infections (otitis media), or pneumonia, during their first three years of life. The children were also tested for respiratory syncytial virus (RSV), rhinovirus or enterovirus – all of which can cause respiratory infections – if they experienced three or more days of coughing, wheezing, or shortness of breath at any point during early childhood.

When Brustad and his colleagues examined the health of these children when they were aged 3 to 13, they found that that each infection episode in early childhood was associated with an increased risk of moderate to severe infections and systemic antibiotic treatment during later childhood – independent of social and environmental risk factors.  
 

Coughs, sneezes – future diseases?

The study, which was published in JAMA Network Open, also found that more frequent exposure to colds, middle ear infections, pneumonia, gastrointestinal infection or episodes of fever increased children’s later risk of moderate to severe infections or antibiotic use, while a high burden of upper or lower respiratory tract infection was associated with an increased risk of pneumonia.

“It is important for all pediatricians to discuss these disease trajectories associated with early-life infections with families, knowing that a high infection load in the first years of life may increase the risk of infections in later childhood and a range of other chronic disorders later in life,” the researchers said. “This knowledge may provide the basis for targeted and more focused disease prevention in specific children to address risk factors such as smoking and an unhealthy lifestyle.”

Although they didn’t speculate about the mechanism, separate research has suggested that early-life exposure to respiratory viruses may alter the expression of immune system genes associated with interferons – proteins that are released by immune cells to help defend against viruses – leaving babies more susceptible to future infections.