The number of pedestrians killed while wearing headphones has tripled in the past seven years.

A study published in Injury Prevention reaveled that pedestrian deaths or injuries involving headphones rose from 16 in 2005 to 47 last year. Most of the accidents occurred with men under the age of 30.

Researchers warn that wearing headphones distracts the part of the brain devoted to external events, making pedestrians less cautious.

Hearing what's going on around them could be more important for pedestrians than visual cues, they said.

Other factors may have contributed to the accidents, such as intoxicated pedestrians or driver error.

Researchers said they need more information to determine which group of people are at the highest risk in accidents involving pedestrians.