The NFL offers many health benefits to players superior to other professional sports leagues, according to the Harvard study. (Ron Schwane/AP)

The physical demands are different. The types and severity of injuries are different. And the economics can vary wildly. But there are several common threads shared by professional sports leagues when it comes to health and safety issues, and a new report from the Harvard Law School is seeking to identify, study and compare them.

The study, released Monday by researchers at the Petrie-Flom Center, found that the NFL offers many health benefits superior to other professional sports leagues but identified several areas for improvement. They included improving life insurance offerings, expanding its pension benefit and amending some of the rules that govern inherent and inevitable injuries, such as concussions.

The 255-page report is the largest and most thorough comparative study of its kind, and researchers included information from six pro sports leagues — NFL, NBA, MLB, NHL, MLS and the Canadian Football League — and their respective players’ unions. Though funded by money set aside by the NFL and its players’ union, it wasn’t subject to approval by any of the leagues.

“In terms of employee benefits, we think the NFL actually offers many employee benefits that Fortune 500 companies and many good employers do not,” said Harvard’s Glenn Cohen, one of the study’s co-authors.

While the report praised the league for some of the benefits it offers its current players — such as the right to seek out a second opinion from doctors and players’ ability to choose their own surgeons — it found some of the retirement benefits to be lacking when compared with other leagues. The NFL’s retirement plan benefits are worse than those in MLB and the NBA and NHL, the report stated. For example, baseball players and hockey players are vested in their pensions on the first day they appear in a regular season game; the NFL requires players accrue three years of experience before they’re eligible for retirement benefits, a high bar in a sport with short career spans.

“Given the shortness of the NFL player’s career, that actually ends up excluding a significant number of people from the pension plan,” Cohen said.

MLB, the NBA and the NHL also offer some form of health insurance for life for their retired players. The NFL offers five years of coverage and then COBRA. Cohen says that better health coverage post-career could be especially important right now as Congress considers changes to health care law that could make it more difficult for people with preexisting conditions to qualify for affordable insurance.

“Where players have only played one or two seasons (and perhaps games), there might be questions as to whether it is appropriate to provide lifetime health insurance to someone who was employed for such a short period of time,” states the report, which was co-written with Christopher Deubert and Holly Fernandez Lynch. “On the other hand, only a few games or seasons can have life-lasting effects on a player. One option worth considering is tiering health insurance benefits and allowing those with less Credited Seasons to qualify for some but not full benefits.”

Among the report’s top recommendations: a change to injury rules that would treat a player recovering from a concussion differently than those who’ve suffered other injuries. The report notes that MLB now offers a short-term seven-day disabled list for players who’ve suffered a concussion. Noting that concussions are far more prevalent in football, researchers recommended the NFL adopt a similar policy.

The league considered a similar rule change at its most recent owners’ meetings in March. The Washington Redskins proposed permitting teams to place a concussed player on an exempt list, allowing the clubs to replace the player temporarily until he’s cleared to return. But the owners did not approve the suggestion.

“My hope is that will be something that will be revisited,” Cohen said.

The report is the latest piece in a broader Harvard project called the Football Player Health Study, which is funded by money set aside by the collective bargaining agreement between players and owners. The NFL Players Association contracted with Harvard in 2014 to study multiple facets of health and safety issues in the NFL and several more reports are in the works.