Distributed March 28, 2002
For Immediate Release

News Service Contact: Kristen Cole

Third-graders better equipped to handle stress if early to bed, study says

Measuring the hormone cortisol, blood pressure and perceptions of events, researchers at Brown University found that third-grade girls who went to bed before 9 p.m. showed more adaptive responses to stress than those who stayed up later. The study included 138 girls in New York City.

PROVIDENCE, R.I. — Being in bed by 9 p.m. makes a youngster better able to respond to stress than those who stay up later, according to a new Brown University study.

The study included 138 third-grade girls, ages 8 and 9, residing in New York City. Researchers measured their levels of the stress hormone cortisol, blood pressure, and perceptions in relation to three stressful tasks during a home visit.

“Kids typically encounter all sorts of stressors in their lives,” said Vincent F. Capaldi, the study’s lead researcher and a Brown undergraduate, who presented his findings March 14 at the American Psychosomatic Society meeting. “If you are able to cope with stress, you are better able to learn and less prone to illness.”

Girls in the study completed a block design task that challenged their intellect, applied a cold press to their foreheads that mimicked a physical stress, and had a conversation with their mothers on a topic about which they disagreed. The girls chose the topic from a list of issues such as manners, telephone calls, behavior toward siblings, behavior toward mother, going to church, and taking care of tapes and compact discs.

Levels of cortisol were measured at the beginning of the interview and after each stressful task. Girls with earlier bedtimes registered a greater initial spike and steeper decline in cortisol when faced with stress as compared to girls with later bedtimes. That strong response suggests girls with earlier bedtimes have a better regulated response to stress compared to the more “sluggish” response of those with later bedtimes, said Capaldi.

Researchers also found a direct correlation between earlier bedtimes and lower blood pressure. Blood pressure readings were taken at the beginning of the study and following the block design task and cold press. Both systolic and diastolic blood pressure responses to stress increased with later bedtimes.

The third measure – the girls’ perception of stressor aversiveness – was gauged after a cold press was applied. The third-graders with earlier bedtimes perceived a cold press placed on the forehead as more aversive than girls with later bedtimes.

The latest bedtime among the girls in the study was 1 a.m. The youngsters were interviewed on school nights and all awoke around the same time the next morning, said Capaldi.

Previous research has shown associations between sleep and stress in adults but few investigations have looked at the relationship in children. More research is needed to determine whether other factors shared among the girls who go to bed earlier may be linked to the lower stress levels, said Capaldi.

Capaldi worked with Laura Stroud, assistant professor of psychiatry and human behavior, and Raymond Niaura, professor of psychiatry and human behavior, at the Brown Medical School; and Jeanne Brooks-Gunn, the Virginia and Leonard Marx Professor of Child Development and Education at Teachers College of Columbia University. Brooks-Gunn collected the data as part of a larger, longitudinal study of New York City girls.

The research was supported by the National Institute of Child Health and Human Development (NICHD), a National Alliance for Research on Schizophrenia and Depression (NARSAD) Junior Investigator Award, and Research at Brown Grant.