Children’s soft drinks linked to shorter sleep and differences in brain structure

A study of more than 9,600 children found that higher caffeine intake, largely from soft drinks, was associated with less sleep and small differences in brain structure, although it did not prove cause and effect.

A study led by researchers at King’s College London has found that children aged nine to 11 who consumed more caffeine tended to sleep for shorter periods and showed small differences in brain structure, with the strongest source of caffeine coming from soft drinks. The findings, published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, add to concerns about how everyday drinks may affect children’s sleep and development.

The study tracked 9,632 children and asked them about their weekly intake of caffeine-containing drinks, including coffee, tea and soft drinks, while parents reported average sleep duration. The researchers used MRI scans to measure cortical thickness and cortical surface area, two features of the brain’s outer layer that are linked to thinking, attention, decision-making and emotional regulation. They found that higher caffeine consumption was associated with reduced cortical surface area in 22 regions across the brain, even after accounting for family income and parents’ education.

Shorter sleep appeared to be part of the picture as well. Children who consumed more caffeine generally slept less, and reduced sleep was itself linked to smaller cortical surface area. The researchers said these two factors helped explain some of the association between greater caffeine intake and later mental health problems, including difficulties with attention, mood and behaviour, over the following six months. After 18 months, the relationship between cortical surface area and mental health remained, although the sleep-related link was no longer seen in the same analysis.

The findings do not prove that caffeine directly causes changes in brain structure or psychological difficulties. The King’s College London team said it is difficult to separate caffeine from other features of soft drinks, such as high sugar content, and from broader lifestyle patterns that may accompany regular consumption. That caution is echoed by other research, including a University of Basel study suggesting some caffeine-related changes in grey matter may be temporary, and earlier work indicating that caffeine exposure before birth can be associated with later structural brain differences. Taken together, the studies point to the need for more research on how caffeine affects children, particularly when it is consumed through drinks that may seem harmless.