Men who played professional football for a median 5 years showed no special mortality risk in the following decades, versus athletes who played just a few games in the National Football League (NFL), researchers found in a retrospective study.

NFL players with significant careers and those hired to play three game during a strike had similar rates of death over 30-year follow-up (4.9% versus 4.2%, adjusted HR 1.38, 95% CI 0.95-1.99), according to a group led by Atheendar Venkataramani, MD, PhD, of University of Pennsylvania in Philadelphia.

“Given the small number of events, analysis of longer periods of follow-up may be informative,” the authors noted in their study published online in the Journal of the American Medical Association. There were just 181 deaths in the whole cohort, leaving the analysis possibly underpowered; the oldest men in both cohorts were in their mid- to late-50s when the analysis was performed, the investigators acknowledged.

The temporary players in the study were the 879 replacements hired to play during a 3-week NFL player strike in 1987. A temporary player was typically a former college football player, someone released from an NFL team during the preseason, or a former player from a rival league.

This group was compared with 2,933 NFL professionals who started their league careers from 1982 to 1992, with median careers of 5 seasons (interquartile range 2-8).

“NFL replacement players in the 1987 season serve as an appropriate comparison group for career NFL players under the assumption that replacement players were experienced athletes fit enough to obtain an NFL roster position with the exit of another professional athlete, but relatively unexposed to an NFL career (i.e., expected to play at most three games),” Venkataramani’s group wrote.

“The cleverly conceived cohort of replacement players had a much lower ‘dose’ of head trauma and other factors related to a career in the NFL than long-time professional players and presumably returned to much less physically demanding jobs after their participation as NFL replacement players,” agreed Steven DeKosky, MD, of the University of Florida in Gainesville, in an accompanying editorial.

Among career NFL players, the most common causes of death were cardiometabolic disease (35.4%), transportation injuries (13.9%), unintentional injuries (10.4%), and cancer (10.4%). For the replacements, the leading causes were cardiometabolic disease (51.4%), self-harm and interpersonal violence (13.5%), and cancer (10.8%).

Notably, the sole neurological cause of death was amyotrophic lateral sclerosis, responsible for 4.9% of deaths in the career NFL player group and none among replacement players.

DeKosky commented that “no dementia cases were reported as the cause of death in this 1982-1992 cohort despite concerns about chronic traumatic encephalopathy (CTE), which had not become a recognized issue in football until a little more than 10 years ago.”

“Although the life expectancy of professional football players was not significantly reduced based on the current evidence, the health of professional athletes should remain a focus of future research. Clinicians and researchers should now turn to the pressing issues of understanding how such repeated trauma leads to manifestations of neurodegenerative disease (and sometimes overlapping cognitive, neuropsychiatric, and movement disorders such as parkinsonism, tremor, and depression) and why and how altered tau protein plays a role in CTE,” he urged.

“There have been repeated calls for large longitudinal studies of former players. Some studies designed to address this issue are under way with the help and cooperation of former players. Such studies will help determine the actual incidence and prevalence of these neurodegenerative diseases and will provide both a perspective on the real risks associated with repeated subconcussive brain trauma and an understanding of the susceptibility to them,” according to DeKosky.

Venkataramani and colleagues said that the possibility that baseline differences may have biased the results despite adjustment was another major limitation of their study.