WASHINGTON (AP) — Ding Jiaxi knew he would spend his 57th birthday alone in a Chinese prison cell, without a phone call from family or a chance to stretch in the sunlight.

It was the activist’s fifth year in those conditions. Despite letters assuring his family in the United States that he was healthy, his wife, Sophie Luo, was not convinced.

“I’m really worried about his health, because he was tortured before,” Luo told The Associated Press from Washington.

Luo shared details about her husband’s plight before his birthday Saturday, casting light on the harsh treatment endured by the country’s jailed political prisoners, who are often deprived of rights such as outdoor exercise and contact with loved ones, according to families and human rights groups.

Beijing has said prisoners’ legal rights are protected in accordance with Chinese law. The Chinese Embassy in Washington did not immediately respond to an email seeking comment.

Ding, a key member of the now-defunct New Citizen’s Movement that sought to promote democracy and civil society in China, was detained in December 2019 after taking part in an informal gathering in the southeastern city of Xiamen to discuss current affairs. He was sentenced to 12 years in prison in April 2023 on charges of subverting state power.

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Maya Wang, interim China director for the rights advocacy group Human Rights Watch, called harsh treatment “all common fare” for China’s political prisoners.

“Unfortunately, the mistreatment is very common, and it has gotten worse under Chinese President Xi Jinping,” Wang said. Political prisoners have been tortured, deprived of access to lawyers and given “very little” contact with their families, she said, adding that the secrecy has made it easier for abuse against prisoners to continue and their health to suffer.

Rep. Adam Schiff, who serves on a bipartisan congressional human rights commission, urged Ding’s release.

“Once again, he will be alone in a prison in Hubei Province in China. He will be separated from his loved ones — his wife and children. He will mark the passing of yet another birthday in isolation — his fifth in prison,” Schiff, D-Calif., said in a statement released Friday.

Luo said she has not been allowed to speak with her husband on the phone since he was taken away by authorities in 2019. Since then, “I haven’t heard his voice,” said Luo, who moved to the U.S. with the couple’s two children soon after Ding was detained the first time in 2013.

It was only this March that she received his first letter. In letters, Ding has not been allowed to write about his case, how he has been treated in prison or any other subject deemed sensitive by the Chinese government, Luo said.

She said she could not believe Ding was banned from leaving his cell to go out for exercise. “This is really bad for his health,” Luo said. “Every prisoner in China should have the right to be let out for exercise. Why can’t he have that?”

And she lamented on the absence of Ding from the lives of their two daughters. “He can’t be with the girls when they needed a father most,” she said. “It’s really a big loss.”