British researchers may be a step closer to solving the mystery of sudden infant death syndrome, in which apparently healthy infants die in their sleep.
They found significantly higher levels of two types of bacteria - Staphylococcus aureus and Escherichia coli - in autopsy samples from SIDS cases, compared with those from baby deaths attributed to known causes.
Infections have long been suspected in the unexplained deaths. But the new study, being published today in The Lancet, represents one of the most thorough assessments yet of this potential reason behind the fatalities.
Researchers conducted a systematic review of more than 500 autopsies performed between 1996 and 2005 at the Great Ormond Street Hospital for Children in London.
"Our findings suggest that microbes or microbial products could be related ... to a proportion of unexplained sudden unexpected deaths in infancy," they write.
The risk of SIDS tends to peak at eight to 10 weeks of age - a time when infants have immature immune systems that could leave them vulnerable to foreign organisms.
Even so, researchers are careful to point out "the mere detection of pathogens does not necessarily indicate the cause of death." They say more study is needed.
Many factors could play a role. For instance, previous studies have linked the child's position (face down), a smoker in the household and sleeping in the parents' bed to an elevated rate of crib death.
"It's possible that known risk factors for SIDS, such as overheating, co-sleeping, smoking may influence the growth of bacteria in these infants," Nigel Klein, one of the researchers, said in an e-mail interview.
In the meantime, he added, parents should stick to established safety precautions, which can be found at http://www.sids.org.uk.
Teenagers are much more likely than adults to suffer from fainting spells and other adverse effects when they donate blood, according to a study published in the Journal of the American Medical Association. "Most reactions are mild, but a handful experience more significant complications resulting from fainting and falling," said Anne Eder, lead author of the study and executive medical officer of the American Red Cross in Washington, D.C.
Some teens have suffered concussions, received cuts deep enough to require stitches or broken bones because they collapsed in an unconscious state.
Those who had adverse reactions, including a dizzy spell or a slight bruise from the needle, were less inclined to donate blood again, the study revealed. The loss of potential donors is a big concern for the medical system, which occasionally faces blood shortages, Dr. Eder said.
Over all, the study found 10.7 per cent of teens aged 16 or 17 experience side effects within an hour of giving blood. In the 18-to-19 age group, 8.3 per cent suffer from reactions. Those 20 and older have a complication rate of 2.8 per cent. (In Canada, blood donors must be at least 17 years of age and no older than 71.)
Dr. Eder noted that earlier research has shown "the way the young respond to stress differs" from how adults respond, and the withdrawal of blood could be considered a stress on the body. Teens are also more likely to faint if they see others do so - a condition known as "epidemic fainting."
To reduce the risk of serious complications, donors should get adequate sleep, nutrition and extra fluids the previous day, she said. They should also be closely observed in the period after blood is withdrawn.