U2 drummer Larry Mullen Jr has been diagnosed with dyscalculia.
The 63-year-old rocker has revealed he's spent years struggling with numbers because the learning disability makes maths very difficult for him and it has even affected his ability to stay in time when performing because he finds it hard to count the bars.
He told Radio Times magazine: "I've always known that there's something not particularly right with the way that I deal with numbers. I'm numerically challenged.
"And I realised recently that I have dyscalculia … so I can't add, I can't count. I had to find ways of doing this, and counting bars is like climbing Everest.
"And when people watch me play sometimes, they say: 'You look pained'. I am pained because I'm trying to count the bars."
The drummer was forced to miss U2's residency at The Sphere in Las Vegas this year after undergoing neck surgery, but he's on the mend and looking forward to getting back to work with the band recording a new album and the possibility of another tour.
He added to the publication: "I don’t think it will be what we normally do. I would hope it would be something different. But I’m excited to get back in some capacity."
Larry's bandmate Adam Clayton recently gave an update on his condition, telling The Sun newspaper: "[Larry is] back on his stool. Look, we are a little bit like athletes, but have a longer shelf life.
"Larry’s body had taken a battering over the years and his primary issue was pain. He’s finally feeling much better and is very enthusiastic about playing again."
Adam added: "I feel, I hope not mistakenly, that we still have a lot to give. No matter where our lives have led us, the constant is mucking about in a studio, creating music together. That is the greatest reward."