Infants with elevated testosterone levels may face a higher risk of sudden infant death syndrome (SIDS), a new study suggests.

Researchers found infants who died from SIDS have 50-120 percent higher testosterone levels in their blood than infants who died from other causes.

Previous studies have suggested that higher than normal levels of the male sex hormone may cause depressed breathing during sleep, which researchers say may in turn contribute to SIDS risk.

"These results may be important for better understanding of SIDS because the known relationship between testosterone and breathing during sleep provides a mechanism that potentially contributes to SIDS," says researcher Michael Emery, PhD, of the University of Washington, in a news release.

SIDS is one of the leading causes of death among infants 1 week to 1 year old. Although the number of SIDS deaths has decreased in recent years due to increased awareness of proper infant sleeping position (on the back), researchers say the exact cause of SIDS is unknown.

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SIDS Linked to Testosterone

In the study, which appears in The Journal of Pediatrics, researchers measured blood levels of estradiol (an estrogen hormone) and testosterone in 127 infants who had died of SIDS and 42 infants who died of other causes.

The results showed that testosterone levels in male SIDS infants were about 120 percent higher than in non-SIDS infants and 50 percent higher in female SIDS infants than non-SIDS infants.

Estradiol levels did not differ between the two groups.

Researchers say the results suggest that more studies are needed to examine the possible use of testosterone levels as an indicator of SIDS risk.

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By Jennifer Warner, reviewed by Louise Chang, MD

SOURCES: Emery, M. The Journal of Pediatrics, November 2005; vol 147: pp 586-591. News release, The Journal of Pediatrics.