The family of Canadian pastor Hyeon Soo Lim, who was sentenced to hard labor for life in North Korea last year, have revealed they fear his health may be failing, as he suffers from high blood pressure and other serious health issues.

As earlier reported, Lim had been doing humanitarian work in North Korea since 1997 and had visited the isolated country more than 100 times, according to his Toronto church, the 3,000-member Light Korean Presbyterian Church.

North Korea's highest court said Lim, 60, had attempted to overthrow the government and undermine its social system with "religious activities" for the past 18 years, China's official Xinhua news agency reported. At the time of his capture, the pastor had a "very serious health problem, very high blood pressure", his church said.

Last August, Lim was forced to confess to committing crimes against the state in a videoed confession in front of the congregation at Pyongyang's Pongsu Church. The pastor  was later sentenced to life in prison and hard labor in a court hearing that took place Dec. 16, 2015.

During a January interview with CNN, the pastor revealed that he works eight hours a day, six days a week, with rest breaks, digging holes for the planting of apple trees in the prison orchard.

"I wasn't originally a laborer, so the labor was hard at first, but now I've gotten used to it," Lim said at the time. 

Earlier this week, a delegation of Canadian diplomats were once again able to meet with Lim in in Pyongyang, CNN reports.

According to the family's spokesperson, Lisa Pak, the Canadian officials who visited with Lim feel as though "his health does now seem to be of concern." Pak also said there was concern over the pastor's mental state, as he remains in total isolation. Thus far, he has not seen any other prisoners or had any contact with his family.

"While it is good news to hear that Canada has sent a delegation into Pyongyang this past week, we are hoping to hear the best news, that Reverend Lim will be returning home," Pak said. "We trust that Canada is doing all they can to secure his release and urge Canadian officials to continue engaging in diplomatic talks at the highest levels possible."

Joseph Pickerill, the spokesman for Foreign Minister Stéphane Dion, told CBC News that the Canadian government is concerned for Lim's "rights and well-being."

"Consular officials are providing assistance to Mr. Lim and his family. We are grateful that we were able to visit him," Pickerill said. "In the interest of Mr. Lim's case, no further information can be shared."

Despite his bleak circumstances, the pastor told CNN in January that he continues to pray for the unification of North and South Korea, and that no one will ever have to suffer through the same experience he has.

"I hope I can go home someday," Lim said. "Nobody knows if I will ever go home, but that is my hope. I miss my family. I am longing to see them again, and my congregation."

Speaking to the Daily NK, a friend of Pastor Lim and defector from North Korea said he knew the 60-year-old pastor in Canada and would go on trips with him, attend his sermons and support his work. He recalled how the pastor cared for the people of North Korea - even risking his own life to help them.

"He really helped people like me who are from North Korea a lot. In some ways, I would say a lot of people from the North managed to get permanent residency in Canada thanks to his help. He provided a lot of financial help but also supported us so we would be able to settle down quickly in Canada. Defectors who were able to get permanent residency thanks to Pastor Lim now have stable lives in Canada."

For the 14th consecutive year, North Korea topped Open Door USA's World Watch List of countries where Christians face the most persecution.

"Christianity is not only seen as 'opium for the people,' as is normal for all communist states, it is also seen as deeply Western and despicable," reads the report. "Christians try to hide their faith as far as possible to avoid arrest and being sent to labor camps with horrific conditions. Thus, one's Christian faith usually remains a well-protected secret, and most parents refrain from introducing their children to the Christian faith in order to make sure that nothing slips their tongue when they are asked."