Sitting at your desk all day or on your sofa watching TV could make you stupid, scientists have suggested.

科学家指出，终日坐在桌前或者坐在沙发上看电视会让你变傻。

Researchers have discovered those with a sedentary lifestyle have a smaller brain region important in forming memories.

The study, by researchers at the University of California at Los Angeles, adds to a growing list about the dangers of sitting for too long.

An array of evidence has already linked the bad habit to heart disease, diabetes, several forms of cancer and an early death in recent years.

But the new research, derived from 35 participants, suggests sitting for too long could even boost the risk of dementia.

Those with the lazy lifestyles had less grey matter in the medial temporal lobe (MTL) - even if they went for regular brisk walks, cycle rides or jogs.

A decline in this area has repeatedly been shown to be an early warning sign of Alzheimer's disease in middle-aged and elderly patients.

The study, published in PLOS ONE, quizzed the volunteers, who were aged between 45 and 75, about their levels of exercise.