IF YOU are reluctant to leave bed on a dark, winter morning, stay right in there. People who wake up early in winters might be cutting short their required sleep, inviting unforeseen health

problems (New Scientist, Vol 140, No 1899). Researchers say the natural sleeping patterns of humans are strikingly similar to those of chipmunks and other animals, which sleep for long

periods during winter. But, say Thomas Wehr and colleagues at the National Institute of Mental Health in Bethesda, USA, getting up early in winter becomes a habit because of artificial

lighting. This may be forcing humans into unnatural sleeping habits, disrupting seasonal variations in sleep patterns and causing widespread sleep deprivation. The researchers found that