Early-Onset Asthma May Slow Memory Development

Children with asthma scored significantly lower than those without asthma on measures of episodic memory, based on longitudinal data from nearly 500 individuals.

Animal models have shown associations between asthma and memory problems, but data for children are lacking, wrote Nicholas J. Christopher-Hayes, MA, of the University of California, Davis, and colleagues.

“Asthma is very frequent among children, and there is mounting evidence from rodent models that asthma may result in neural injury in the hippocampus, which in turn may cause memory loss,” Christopher-Hayes said in an interview. “Although there is also a good amount of research with older adults, very little research has been done with children, the period that is most frequently linked to asthma onset,” he said. Therefore, the researchers leveraged a large national study on child development to examine development of memory as a function of asthma exposure.

In this study published in JAMA Network Open, the researchers conducted both a longitudinal and cross-sectional analysis of data from the Adolescent Brain Cognitive Development Study, which began in 2015. Children were enrolled at ages 9-10 years with a follow-up assessment 1-2 years later.

The participants were categorized as early childhood-onset asthma (asthma at baseline and follow-up), later childhood-onset asthma (asthma at follow-up only), or no asthma history. The primary outcome of the longitudinal analysis was episodic memory. Approximately half of the participants were boys, and slightly more than half were White.

Among 474 children reviewed in the longitudinal analysis, 135 had early-onset asthma, 102 had later-onset asthma, and 237 had no asthma and served as control individuals. Overall, those with early-onset asthma showed significantly lower rates of longitudinal memory improvements at follow-up compared with the comparison group (P

Developmental memory improvement in children with later-onset asthma was not significantly different from the control individuals. 

Secondary outcomes included processing speed and inhibition, and attention. In a cross-sectional analysis with a larger sample of 2062 children from the same database (1031 with any asthma), those with asthma scored significantly lower on measures not only of episodic memory but also processing speed and inhibition/attention than children with no asthma, with P values of .04, .01, and .02, respectively.

The results were limited by several factors, including the reliance on parent reports for indicators of asthma and the lack of data on the potential effect of prescription corticosteroid use on neurocognitive development, the researchers noted.

The mechanism behind the association remains unclear; the inflammation associated with asthma may disrupt neural processing and manifest as cognitive dysfunction, as has been seen in rodent models of asthma, the researchers wrote. “It is possible that associations between asthma and developmental trajectories emerge earlier for memory, perhaps due to its sensitivity to subtle hippocampal injury,” they noted.

Longer follow-up studies are needed to fully understand how childhood asthma predicts memory declines or difficulties in childhood and beyond, Christopher-Hayes told Medscape Medical News. “We also need additional studies to understand why children who were diagnosed earlier and had asthma for longer seem to be particularly affected,” he said.

The results of this study were consistent with previous findings and therefore not surprising, said senior author Simona Ghetti, PhD, a professor of psychology at the University of California, Davis, in an interview. However, the finding that the extent of exposure to asthma was associated with slower memory improvement in childhood was striking, she said. That children with an earlier asthma onset who had disease indicators for a longer period showed a slower development of memory over time, suggests that asthma exposure may affect the developmental trajectory of memory, Ghetti noted. 

“Recommendations to clinicians are premature because we need a better understanding of the boundary conditions, such as the minimal level of asthma exposure that might generate memory difficulties,” Ghetti told Medscape Medical News.

“Nevertheless, our results underscore the importance of looking at asthma as a potential source of cognitive difficulty in children,” she said.

Asthma’s Extensive Effect

Evidence is mounting that a diagnosis of asthma may have implications outside the pulmonary system, said Diego J. Maselli, MD, professor and chief of the Division of Pulmonary Diseases & Critical Care at UT Health, San Antonio, in an interview. 

“Asthmatics may be at risk of nasal polyps, allergic rhinitis, and other allergic conditions, but there is emerging of evidence inflammation associated with asthma may affect other organ systems,” said Maselli, who was not involved in the study.

“For example, chronic inflammation in asthmatics may increase the risk of cardiovascular disease,” he said.

Although less is known about the effects of asthma on the nervous system, animal models suggest that inflammation associated with asthma may result in neuronal injury and potential effects on memory, said Maselli.

The findings of this study provide evidence of potential detrimental effects on the memory of children with asthma but should be interpreted with caution, Maselli said. “Children with chronic medical conditions may have an inherent disadvantage compared with their peers due to the burden of their disease, medication utilization and side effects, absenteeism from school, physical limitations, and other disease-specific circumstances,” he noted.

“Uncontrolled asthma, in particular, has strong links to low socioeconomic factors that are closely tied to access to adequate medical care, nutrition, educational institutions, and other relevant contributors to normal cognitive development,” Maselli said. Although the authors account for some of these socioeconomic factors by evaluating income and race, other variables may have influenced the results, he added.

Overall, this study’s findings suggested that the diagnosis of asthma in children may be associated with memory deficits and may influence neurodevelopment; however, more research is needed to determine whether the findings are replicated in other cohorts, Maselli told Medscape Medical News. “In particular, evaluating the effects of the severity of asthma and different asthma endotypes would be crucial to identify children with a higher risk of memory or cognitive deficits and confirm these associations,” he said.

This study was funded by the Memory and Plasticity Program at the University of California, Davis, and by a Learning, Memory, and Plasticity Training Program Fellowship grant from the National Institutes of Health. The researchers had no financial conflicts to disclose. Maselli had no financial conflicts to disclose.