Smoke alarms with mom's voice wake kids up faster: study

WASHINGTON: A smoke alarm that broadcasts a mother’s voice would wake children much more quickly than alarms that blast high-pitched tones, a new U.S. study finds.

Sleeping children, as it turns out, are fairly impervious to the screeching of a smoke alarm. Researchers found that most children ages 5 through 8 took more than five minutes to wake up with a standard alarm, as compared with around four seconds when they heard the sound of their mother’s voice, according to the results published in The Journal of Pediatrics.

“The thing that was most remarkable to us was to see a child sleep five minutes through a very loud high-pitched tone, but then sit bolt upright in bed when their mothers voice sounded through the alarm,” said the study’s lead author, Dr. Gary Smith, who directs the Center for Injury Research and Policy at Nationwide Children’s Hospital in Columbus, Ohio. “We didn’t expect the difference to be so dramatic.”

Smith hopes that in future studies, researchers will find that a generic female voice is just as effective at waking young children since that would be an easier and cheaper alarm for companies to design. The current research “is an important step towards optimizing smoke alarms for waking up young children,” he said.

Even though the alarms currently on the market are not optimal for waking kids up, “we want to make it really clear that standard alarms work,” Smith said. “We don’t want to give the impression that parents should stop using the high-pitched tone alarms. They will wake up the adults and they can then rescue the children. They are lifesaving. In this country, about half of the residential fire deaths are in homes without alarms.”

To take a closer look at the effect of a mother’s voice on her sleeping child, Smith and his colleagues recruited 176 children between the ages of 5 and 12 and brought them into the sleep lab for testing. The lab had rooms that were set up to look like a typical bedroom, Smith said.

The children’s brain activity was monitored with electrodes on their scalp and face, and they were allowed to fall into the deepest stage of sleep. Then one of four types of simulated smoke alarm was sounded and researchers measured how long it took for a child to wake up and follow a previously rehearsed escape plan.

The experiment was run four times with each child, each about a week apart, so that all the children were exposed to all four types of alarm: standard high-pitched tone, the mother’s voice with instructions like “wake up” and “get out of bed,” the mother’s voice saying the child’s name, and the mother’s voice saying the child’s name and then giving instructions.

There was no significant difference in time to waking between the three alarms that used the mother’s voice. But there was a very large difference between all three of the maternal voice alarms and the standard alarm.

Maternal voice alarms woke 86 to 91 percent of children, prompting 84 to 86 percent to successfully perform the escape procedure within five minutes of the alarm’s onset. That’s compared to 52 percent of kids waking to the standard alarm and 51 percent escaping.

Nearly 6 percent of kids did not wake to any of the alarms and had to be manually awakened after five minutes.

The study was not designed to determine whether a mother’s voice has a different effect on her child versus any other human voice, the authors note. Further research is also needed to determine how children’s responses are affected by the content of the voice alarm message, they write.

“In real life terms, this could make a big difference,” said Dr. Hiren Muzumdar, director of the Pediatric Sleep Evaluation Center at the Children’s Hospital of Pittsburgh, who wasn’t involved in the study. “It would seem that it could save a lot more kids.”

It might even help save other family members, Muzumdar said. “If a fire starts near a child’s room, the child could go wake up their parents,” he explained.

It wasn’t surprising to Muzumdar that children might sleep through a loud blaring alarm. “Kids have a much higher threshold for arousals,” he said. “In fact, children with significant sleep apnea rarely appear sleepy during the day because their sleep isn’t disturbed. In adults with significant sleep apnea, there is much more daytime sleepiness,” said Muzumdar, who specializes in sleep-breathing disorders.

Though Muzumdar would have expected children to wake more quickly to a mother’s voice, “I would have expected just a little difference,” he said. “But this is a staggering difference. It’s just remarkable.”