“Mild” concussions — including ones that don’t involve a loss of consciousness and that may not even show up on brain scans — can cause persistent memory and attention problems that last for at least a year, a new study has found.

Such concussions — known medically as mild traumatic brain injuries (TBIs) — are more likely to lead to problems at school and a decline in the child’s quality of life, the study also found.

“The overall message emerging from this research is that the group of injuries classified as ‘mild TBIs,’ including sports-related concussions, should not necessarily be treated as minor injuries, which quickly resolve,” writes Dr. Frederick Rivara, a professor and division chief of general pediatrics at the University of Washington in Seattle, in an editorial that accompanied the study.

For the study, researchers at Ohio State University followed 285 children, aged 8 to 15, who were admitted to two Ohio hospitals (one in Cleveland, the other in Columbus) for either TBIs or a fractured arm or leg.

They found that the children who suffered the brain injuries were more likely to show both cognitive symptoms (forgetfulness, inattention) and physical symptoms (headaches, fatigue, dizziness) than the children with the broken bones.

Furthermore, the symptoms, particularly the cognitive ones, persisted in about 20 percent of the TBI children for at least one year (the length of the study). The problems were sometimes severe enough to require that the child receive tutoring, remedial services or other special accommodations at school.

Children whose head injuries had caused them to lose consciousness or who had injury-related abnormalities on brain scans were most at risk. But the symptoms also persisted in other children with TBIs.

The results appeared online Monday in the journal Archives of Pediatrics & Adolescent Medicine.

A serious public health problem

No one should be reassured that “only” 20 percent of the children had lingering symptoms. As the authors of this study point out, more than 500,000 children under the age of 15 in the United States go to the hospital for TBIs each year.

“Even if only a small proportion of children with mild TBI have persistent negative outcomes, then mild TBI is a serious public health problem,” they write.

This study, like all studies, had several limitations. Most notably, the children’s symptoms were determined by questionnaires filled out by their parents, a factor that may have skewed the findings. It may be, for example, that the parents of the children with head injuries were more likely to be on the watch for cognitive problems than parents of children with broken arms or legs.

A need for more answers

This study also follows on the heels of one published in February that found that concussions affect the cognitive abilities of teenagers much more than they do adults, perhaps because those parts of the brain involved in memory and problem solving are still developing during adolescence.

Rivara and the authors of the current study say better tests need to be developed to determine which children with brain injuries need special care. And, of course, more needs to be done to prevent the injuries in the first place.

“Millions of children engage in sports in the United States, and increased physical activity is an important part of the public health message to decrease obesity in both children and adults,” writes Rivara. “Among high school girls, soccer is the most common source of sports-related concussion. How do we promote the engagement of youth in these sports and, at the same time, ensure that they are safe from concussion?”