THURSDAY, Sept. 24 (HealthDay News) -- Infants with severely flat heads caused by their sleep position have a higher-than-normal rate of ear infections, a new study has found.

The recommendation to place babies on their backs to sleep has reduced cases of sudden infant death syndrome but has increased the number of infants with flattening of the back of the head, according to researchers at Wake Forest University Medical Center in North Carolina.

They asked the parents of 1,259 children with what is called positional plagiocephaly about their child's history of ear infections and found that half of the children had at least one ear infection before they were 1 year old. That's similar to the rate in the overall population, they noted.

However, the rate was 54 percent for children with severe flattening, the study found.

In 124 children, the researchers performed a test called a tympanogram to measure pressures within the middle ear. They found a "marked trend" toward an association between ear-infection-related abnormalities and the severity of plagiocephaly.

"The significantly high percentage of tympanogram readings that pointed to otitis media [ear infection] ... suggests an overall malfunction of the middle ear drainage function of the eustachian tube in these children," the researchers wrote.

The study is in the September issue of the Journal of Craniofacial Surgery.

Because ear infections can have a major impact on hearing and other aspects of child development, the researchers noted, further study is needed to learn more about ear infection risk in children with positional plagiocephaly.

More information

The U.S. National Institute on Deafness and Other Communication Disorders has more about ear infection.