Friday’s health and safety news involves updates on key NFL players and some interesting facts on NFL, college and prep concussions:

* New York Jets star cornerback Darrelle Revis, who suffered a concussion during the NFL’s first regular-season week, practiced for the second consecutive day and is listed as probable for Sunday’s game against the Miami Dolphins.

* However, The Associated Press broke the news that Minnesota Vikings linebacker Erin Henderson has been ruled out for Sunday’s game against the San Francisco 49ers because of a concussion he suffered last week.

* The New York Times wrote about how the NFL lets players choose what helmets they wear. However, some teams have deals of their own with helmet manufacturers.

* Bloomberg News reported on a study that says concussions in college football were down by 26 percent last season compared to the 2004 season.

* Reuters offered a big-picture story on high school concussion rules and the difference the Zack Lystedt Law has made among prep football teams.

* Former Bears linebacker Hunter Hillenmeyer, whose career was ended early because of head injuries, told Chicago Parent magazine that concussion awareness has become his cause.

* Lexington,N.C., Medical Center is creating a network of concussion experts, according to the Lexington Dispatch.

* And the Melbourne Herald-Sun wrote about what it called a concussion “time bomb” in Australian Rules Football.

Dr Chris Hatherly, the national research manager for Alzheimer’s Australia, told The Courier-Mail there was “conclusive evidence” repeated head injuries dramatically increased the risk of developing Alzheimer’s and dementia, with a severe concussion increasing the risk by 4.5 times.

– Bill Bradley, contributing editor