New research suggests they're at high risk for sleep apnea, which causes sufferers to stop breathing repeatedly during sleep and can leave them tired during the day.
Based on results of overnight apnea testing of 52 players, researchers concluded about 14 percent of all professional football players suffer from apnea, and 34 percent of those considered at "high risk" have the condition. Risk is based not only on someone's size, but also other factors such as whether he snores, appears to stop breathing during sleep or wakes up tired.
The high proportion of young players with the condition -- the average age was 25 -- surprised researchers, who say the finding suggests apnea may be much more prevalent among heavy younger people than previously believed.
"The thing that's important for us is that these are very young men and these guys are supposed to be in the best shape, and yet they have unrecognized sleep apnea," says researcher Dr. Charles F.P. George, a professor of medicine at the University of Western Ontario.
Although size is not the only factor, the heavier you are, the more likely you will have sleep apnea, George says.
That helps explain why huge linemen faced the greatest risk: They accounted for 12 of the 14 cases of apnea among the 52 players, says the study, which appears in the Jan. 23 issue of The New England Journal of Medicine. The other two players with apnea were a tight end and a running back.
Weight can press in on the neck and airway tissues, and when the muscles relax, the airway can narrow, George explains. The size and shape of the airway also appears to influence the risk of apnea, he adds.
Of all the players studied, the linemen had the largest neck circumference (about 19.1 inches), the highest body-mass index (or height-weight ratio) and the highest blood pressure.
George notes that NFL players aren't exactly slimming down either. The number of players weighing more than 300 pounds has grown from just a handful 15 years ago to more than 330 today.
Researchers divided the players into high- and low-risk groups. Thirteen of the 38, or more than a third, in the high-risk group had apnea, compared with one of 14 in the low-risk group.
The study didn't measure sleep apnea's effect on player performance, but George notes other research has linked apnea to drivers falling asleep at the wheel and to auto crashes. Sleep apnea also is a known risk factor for hypertension and, in turn, stroke or heart attack.
George stresses the condition is treatable, but is often not recognized in young, otherwise healthy people. Sleep apnea treatments include use of a device that forces air into the lungs and, in some cases, surgery.
Dr. David Rapoport, medical director of the Sleep Disorders Center at the New York University School of Medicine, says sleep apnea affects about 4 percent to 5 percent of the general population, typically people aged 40 to 60.
However, Rapoport says, the study shows overweight people with big bellies and heavy necks have a greater risk of sleep apnea if they have other symptoms such as snoring or daytime sleepiness.
That holds true, he says, even for young NFL players.
"There's no question we're breeding them bigger and better," says Rapoport. But, he adds, "these players are potentially paying a price for being the thing that wins football games."
The National Sleep Foundation has the football lineman report.