ALBANY: Students who rely on working at night to improve their grades might want to sleep on that strategy: a new survey in the US says those who never study all night have slightly higher grades than those who do.

A survey of 120 students at St Lawrence University, a small liberal arts college in northern New York, found that students who have never pulled an all-nighter have higher grades than those that have not.

The survey found those who never worked all night had a 3.1 grade point average, with 4 being the highest on the scale, compared with 2.9 for those who have.

The study, by assistant professor of psychology Pamela Thacher, is to be included in the January issue of Behavioral Sleep Medicine . "It's not a big difference, but it's pretty striking," Thacher said. "I am primarily a sleep researcher and I know nobody thinks clearly at 4 in the morning. You think you do, but you can't."

A second study by Thacher, a clinical psychologist, had "extremely similar" results showing lower grades among the sleep skippers. Many college students, of course, have inadequate or irregular sleep, for reasons ranging from excessive caffeine to poor time management.

Prav Chatani, a St Lawrence sophomore who wasn't involved in either study, said the findings made sense. The neuroscience major has been pulling fewer all-nighters, but recently stayed up until "around 4 or 5 in the morning" to prepare for an organic chemistry test and a neuroscience presentation, he said.