They survey, published in the January issue of Pediatrics, included nearly 200 7th- through 9th-grade students who recorded their sleep patterns and their daily intake of caffeinated drinks and foods over two weeks.

The average intake of caffeine was just 63 milligrams (mg)--equivalent to about one-half of a cup of coffee. Children who reported higher intakes of caffeine were found to sleep fewer hours, were more likely to wake during the night and tended to be sleepier during the day.

The results of the study indicate that even small amounts of caffeine can have effects on children and call into question the trend to place soda machines in US middle schools and high schools. While these machines may be welcome by students and generate cash for school boards, they can affect students' sleep, the study authors conclude.

"The increasing availability of soft drink dispensing machines in schools is apparently welcomed by students and is profitable to school boards, but our findings suggest that it may be interfering with the nighttime sleep of teenagers," Dr. Charles P. Pollack from Ohio State University in Columbus, Ohio and David Bright, a student, write.

"It may eventually become appropriate to limit the caffeine contents of soft drinks or restrict the types of beverages that are promoted to teenagers," they add.

In other findings, most students (57%) reported consuming an average of 0 mg to 50 mg of caffeine daily, but daily consumption was as high as 800 mg. Boys tended to consume more caffeine than girls--about 70 mg daily, compared with 55 mg daily.

Caffeine consumption peaked at 77 mg on Saturdays and fell to an average low of 54 mg on Wednesday, the study found.

SOURCE: Pediatrics 2003;111:42-46.