Wellington, Apr 18 (IANS): People feel as though they have jet-lag after surgery, which could be due to the effect of general anaesthesia that alters genetic activity controlling the bio-clock, a study reveals.

"Our work shows that general anaesthesia effectively shifts you to a different time zone, producing chemically-induced jet-lag. It provides a scientific explanation for why people wake up from surgery feeling as though very little time has passed," explained Guy Warman, anaesthesiologist at the University of Auckland's School of Biological Sciences, who led the study.

The effect persists for at least three days, even in the presence of strong light cues telling the brain the correct time of day, the journal Proceedings of the National Academy of Sciences reported.

"It is known that after anaesthesia people's biological clocks are disrupted, and this can compromise their sleep pattern and mood as well as wound healing and immune function. By understanding why this happens we can work out how to treat it and potentially improve post-operative recovery," said Warman, according to a university statement.

The work was done using honey bees. "It might sound unusual, but in fact bees are an ideal species to study time perception. Honey bees have an amazingly accurate sense of time, which allows them to forage and find flowers in the right place at the right time of the day," said Warman.

"By looking at their behaviour we can get a clear idea of what time of day they think it is, and quantify the effects of anaesthesia. An added advantage is that their biological clocks work in a very similar way to mammals," added Warman.

Researchers are already putting their findings to use in clinical studies in New Zealand, examining the extent of post-operative jet-lag in patients and how it may be treated.