Inflammation Influences the Link Between Sleep and ADHD

Isabel Morales-Muñoz, PhD, MSc

According to results from a new study, sleep problems in early childhood indicated a probable diagnosis of attention deficit and hyperactivity disorder (ADHD) at the age of 10. In addition to the association between early childhood sleep and ADHD diagnosis, investigators also evaluated markers that showed potential to mediate the associations.

A team led by Isabel Morales-Muñoz, PhD, MSc, Institute for Mental Health, University of Birmingham, Birmingham, UK, performed a cohort study to determine whether circulating inflammatory markers in childhood play a role in the link between sleep and ADHD.

Investigators explained sleep problems are experienced by 70%-85% of children with ADHD. Fragmented sleep, bedtime resistance and sleep-onset insomnia tend to occur in children before ADHD symptoms.

Sleep-Related Symptoms as Precursors

For this analysis, data on children 10 years of age were obtained from the Avon Longitudinal Study of Parents and Children. At 3.5 years parent-report duration, night awakening frequency and regular sleep routines were included.

In order to identify children that had clinically relevant ADHD symptoms, or a probable ADHD diagnosis the Development and Wellbeing Assessment was utilized. At 9 years, inflammatory blood markers interleukin-6 (IL-6) and C-reactive protein (CRP) were obtained from patient blood samples.

The association between sleep variables at 3.5 years and probable ADHD diagnosis at 10 years was investigated with logistic regression analyses. The potential mediating role of inflammation at 9 years, measured by CRP and IL-6, was also investigated in this relationship.

The Mediation of Sleep and ADHD

Results from the analyses revealed that children had a higher likelihood of having ADHD at the age of 10 if they had irregular sleep routines, shorter nighttime sleep, and higher frequency of of night awakening at 3.5 years.

As for the inflammatory markers, investigators discovered that IL-6 served as a mediator between irregular sleep routines and ADHD, and for the relationship between nighttime awakening and ADHD. Alternatively, CRP did not exhibit any meaningful mediation.

"Several sleep problems in early childhood constitute a risk factor for probable ADHD diagnosis at 10 years," investigators wrote. "Further, these associations are partially mediated by IL-6 at 9 years. These results open a new research vista to the pathophysiology of ADHD and highlight sleep and inflammation as potential preventative targets for ADHD."

The study "The role of inflammation in the prospective associations between early childhood sleep problems and ADHD at 10 years: findings from a UK birth cohort study" was published in the Journal of Child Psychology and Psychiatry.