Babies who routinely sleep on a mattress previously used by another child may be at greater risk of cot death, according to a study published today.

Researchers at the Royal Hospital for Sick Children in Glasgow believe there may be a link between bacteria in used mattresses and cot deaths. Of the 131 cases of cot deaths they looked at, about half of the babies died on used mattresses. And two thirds of the used mattresses had come from another home.

The four-year study published in this week's British Medical Journal found that routine use of an infant mattress previously used by another child was significantly associated with increased risk of sudden death syndrome, especially if the mattress was from another home. The findings back up an earlier survey carried out by researchers at the hospital in 1997.

Dr David Tappin, a paediatrician at the Yorkhill NHS Trust, said: "The most important steps to take to reduce cot death are to put babies on their back to sleep and to stop smoking during pregnancy and keep the baby smoke-free after the birth." His advice to parents was to use a waterproof mattress that was in good condition.