In a statement released Monday after Bae, 46, gave a brief news conference with other detained Americans, Terri Chung of Edmonds, Washington, said it's obvious from the way her brother sat that he is in a lot of pain.
She said the normally cheerful man also has little human contact in the camp, where he was sentenced to a 15-year term for what North Korea has claimed were hostile acts against the state. Chung appealed to North Korean officials to show mercy and release her brother, saying he has confessed and served a longer detainment than any other American since the war. Bae has been held since November 2012.
"As an incredibly friendly and social man, the psychological pain of isolation and worry for his family must weigh on him as much as the physical agony," Chung wrote after news conference. "He is normally cheerful - larger than life - but I could not see that man today."
In a telephone interview with The Associated Press, Chung said the televised interviews are difficult to watch and thinks Bae's body isn't going to be able to withstand much more of the physical labor. Bae also has diabetes and has been moved back and forth to a hospital during his confinement.
Bae's media appearance echoed a telephone conversation Chung had with her brother about three weeks ago, which was her fourth call from him in two years, she said.
"He's eager to come home. His health is not going well. He needs help from the United States government," Chung said, adding she is in regular contact with the State Department.
"We know that they are working on something," she said. "I want to see all the work come to fruition."
National Security Council spokesman Patrick Ventrell said in a statement that the U.S. government continues to work to get Bae and the other Americans released as soon as possible.
Chung said the family has also had some contact with Bae through email, and his responses show he is receiving their notes and getting some medical care.
She called the limited exchange of information and the infrequent television appearances an emotional roller coaster. Each time, Chung hopes his release may be imminent.
"It's past time now to bring him home," Chung said. "He's an American citizen pleading for help. It's difficult watching him pleading repeatedly on TV."