Speaking a few days after former Wales captain Ryan Jones (41) revealed that he had been diagnosed with early onset dementia, Marler said he was against removing the element of danger in rugby and backed players to make informed decisions.
But the 32-year-old recalled how he "broke down" following a Premiership game in 2016 in which he sustained a heavy blow to the head when he went in to tackle Billy Vunipola (29).
"I was out cold and I remember being in the physio room next and the kit-man came in. I broke down and I had no recollection of having kids," Marler told TalkSport.
"It just really scared the life out of me."
Marler said he felt sorry for Jones, who was told by doctors in December that he was one of the worst cases they had seen and that he was also diagnosed with probable chronic traumatic encephalopathy.
"It's awful for Ryan to be told that and be going through that. I've just buried my head in the sand... because it scares me. I just ignore it," Marler said.
"But the more it comes out and the more apparent it becomes in the sport, the more boys are getting diagnosed with this stuff. It's sad.
"There's always going to be that element of danger and you don't want to remove it so that it isn't rugby anymore. But you do want to be well informed going into it.
"As long as I am informed with what the dangers are, I can make an informed choice."
Jones was an integral part of Wales during the 00s and captained the side. In an interview with The Sunday Times, he confided that he felt his world was falling apart after his diagnosis last year.
He said: "I feel like my world is falling apart. I am really scared because I’ve got three children and three step-children and I want to be a fantastic dad.
“I lived 15 years of my life like a superhero and I’m not. I don’t know what the future holds. I am a product of an environment that is all about process and human performance. I’m not able to perform like I could, and I just want to lead a happy, healthy, normal life.
"I feel that’s been taken away and there’s nothing I can do. I can’t train harder, I can’t play the referee, I don’t know what the rules of the game are anymore.”
Last month, organisations like the Rugby Players' Association linked up with the Alzheimer's Society to provide a way of supporting those affected by the disease.