In a study from England, most babies who died from sudden infant death syndrome (SIDS) were sleeping with an adult or another child at the time.

Many of these "co-sleeping" deaths occurred in a potentially hazardous environment, such as in a bed or a sofa shared with an adult who recently used drugs or alcohol, according to the report in the British Medical Journal.

Since the early 1990s, the rate of SIDS in the UK has decreased markedly, but to achieve further gains, specific advice must be given to the public regarding the dangers of co-sleeping arrangements, Dr. Peter Fleming, from the University of Bristol, UK, and colleagues emphasize.

Their findings stem from a 4-year study conducted in a southwest region of England, featuring 4.9 million people and 184,000 births. The study focused on 80 infants who died from SIDS, 87 who were randomly selected from the population, and 82 who had known risk factors for SIDS, such as having young, socially deprived, mothers who smoked, but did not die.

Overall, 54 percent of SIDS infants were sleeping with someone else at the time of death.

By contrast, when the parents in the comparison groups were interviewed, just 20 percent said that their babies had been sleeping with someone else in the preceding 24 hours.

As noted, parental use of drugs and alcohol may have played a role in the association between SIDS and co-sleeping. In 31 percent of SIDS infants, a parent had recently used drugs or alcohol compared with just 3 percent of comparison infants.

Co-sleeping on a sofa was also more common among SIDS infants than among others: 17 versus 1 percent.

Pillow use, swaddling, maternal smoking, preterm birth, and fair or poor health were all more common among SIDS infants than among the other babies.

Public health campaigns to prevent SIDS appear to be having an impact as many known risk factors occurred infrequently in the study, such as covering the infant's head during sleep, exposure to tobacco after birth, use of a pacifier, and sleeping in the side position.

However, use of the belly-down or "prone" position, a well-established risk factor for SIDS and the focus of the "Back to Sleep" campaign started in the 1990s, was still an important factor, seen in 29 percent of SIDS infants compared with 10 percent of comparison babies.

Not everyone, however, agrees fully on the link between bed sharing and SIDS, Dr. Edwin A. Mitchell, from the University of Auckland, New Zealand, notes in a related editorial.

"The major disagreement in the bed sharing debate," he says, "is whether the advice to avoid bed sharing should apply at all times in the first 6 months of life, or whether it is acceptable to condone or even encourage bed sharing in the small group that has not been shown to be at increased risk (infants of mothers who do not smoke, who are aged 3 months or more, and whose mothers have not taken alcohol or drugs and do not co-sleep on a sofa."

Nonetheless, in Mitchell's opinion, "the safest place for an infant to sleep is in a cot beside the parents' bed in the first 6 months of life."