Despite years of education and growing public awareness about head injuries, college football players report having six suspected concussions and 21 so-called "dings" for every diagnosed concussion, with offensive linemen being the least forthcoming to trainers and team personnel, a new study by Harvard University and Boston University researchers has found.

The 27-to-1 ratio underscores the challenges that remain in protecting players in a sport that long has fostered an ethos of playing through injury, especially brain trauma. The study, published in the Journal of Neurotrauma, is based on a survey of 730 Football Championship Series players conducted in 2013.

Among offensive linemen, the rate of diagnosed concussions to suspected concussions and dings was 32-to-1. They suffered 62 percent more suspected concussions and 52 percent more dings than other positions.

An NCAA spokesman was unavailable for comment.

"In my mind, the most important finding is that college football players are intentionally playing through the vast majority of potential concussions," said Chris Nowinski, co-founder of the concussion education group Sports Legacy Institute. "Their intention is influenced by a lack of understanding of the injury [and] the culture of their position, as well as a learned perception that their coach may not support reporting a concussion."

Nowinski, a former offensive lineman in high school who went on to play at Harvard, said the culture of offensive linemen is to see its members as tougher than the other players.

Christine Baugh, a Harvard researcher and the lead author, did not respond to requests for comment, but her group suggested another possible reason for offensive linemen having higher rates of suspected concussions: They reported participating in more full-contact practices than all other position groups, and significantly more than other position groups other than tight ends and defensive linemen.

The survey was conducted at 10 universities in seven states, with the aid of athletic trainers. Athletes were asked about their recollections from the 2012 season, as well as over the course of their football careers. Nowinski said Football Bowl Subdivision programs were invited to participate but only FCS schools provided access.

Offensive line was not the only position that carried an elevated risk. Running backs were most likely to have been diagnosed with a concussion in 2012, although the authors described the difference as not significant from other position groups. However, over the course of their careers, running backs were far more likely to report suffering dings or having their "bell rung."

The authors noted that most of the rules changes at the NFL and NCAA levels that have been adopted to promote safety in recent years are aimed at reducing the frequency of big hits among skill position players -- not the smaller, repetitive hits that might also be damaging and are a feature of line play.

"The most important finding is that college football players are intentionally playing through the vast majority of potential concussions." Chris Nowinski, co-founder of

Sports Legacy Institute

"Examining the extent to which practices may be modified to minimize contact is an important step, and one that has been taken by NCAA conferences such as the Ivy League and PAC-12 and that has recently been suggested for implementation at all institutions by the NCAA's recent Concussion Management Best Practice Guidelines," the authors wrote. "However, understanding that the seemingly routine contact experienced by linemen may be leading to symptoms, it is important that these rules clearly define what is meant by contact practices in order to reduce the brain trauma experienced by all athletes, including linemen."

Concussions and sub-concussive impacts in football have been associated with neurologic impairment, and repetitive concussive injury has been linked to diseases including chronic traumatic encephalopathy (CTE). But until now, differences in head impact outcomes across playing positions were not well understood, the authors noted. The study found that offensive linemen were more likely to feel dizziness, headache and "seeing stars," all of which could be symptoms of a concussion.

The older the player, the less likely he is to disclose a head injury. The study found that freshmen are far more likely than juniors or seniors to believe their coach wants them to report a concussion.

Nearly 80,000 college students play tackle football, which has among the highest rates of concussion by sport. Another 1.1 million play at the high school level, and about 3 million play youth football.

Some studies have found higher rates of reported concussions in high school football than college football, while others have found the opposite, the authors noted.

"I would anticipate that the problem is similar, if not worse, at the high school level," Nowinski said. "A high school player likely has less ability to understand and report a concussion, although I hope that the coach would be more supportive of reporting concussions as the coach is not being paid millions of dollars a year to win."