The Liberal Senate leader says colleague Sen. Joyce Fairbairn deserves “the same respect” for her privacy as anyone else suffering health problems, after it was revealed the senator has required care for 18 months following a diagnosis of dementia.

In a statement, Sen. James Cowan, leader of the opposition in the Senate, said Fairbairn “has developed health challenges of her own, as a result of which she will be unable to take up her legislative duties when the Senate resumes sitting in late September and will go on sick leave.”

Cowan went on: “Members of Parliament, like everyone else, have health issues from time to time and deserve the same respect for their privacy as other Canadians. I am sure that I speak for all of her friends on Parliament Hill and across Canada when I wish her the very best in these trying circumstances.”

At age 73, Fairbairn is two years from the Senate’s mandatory retirement age of 75.

A letter obtained by CTV News Ottawa correspondent Richard Madan indicates that Fairbairn was diagnosed with “dementia of the Alzheimer’s type” and “has declined significantly over the past year.”

The letter, dated Aug. 13, was written by Fairbairn’s niece Patricia McCullagh, who has been acting as her aunt’s agent under her personal directive for her care.

It was sent to Senate Clerk Gary O’Brien and copied to Cowan and Senate Speaker Noel Kinsella, among others.

McCullagh said her aunt “is no longer able to look after herself,” and has had 24-hour, full-time care for the past 18 months.

The letter states that “A declaration of incompetence was signed by her Geriatric Psychiatrist in February 2012.” It also says that Fairbairn’s “awareness and memory have deteriorated further in the past month.”

Fairbairn, a widow, is being cared for in her Lethbridge, Alta. home.

Reports indicate that Fairbairn continued to sit in the Senate until it rose for the summer in late June, voting with the Liberals on at least a dozen pieces of legislation.

Liberal colleagues said Tuesday they struggled with how best to help Fairbairn, including when it might be time for her to take a leave from the Senate.

“You just don't cut someone's just not ethically or morally right," Sen. Jim Munson, a longtime friend and colleague, told The Canadian Press.

"What's happening with Joyce, I find -- like others with Alzheimer's -- that she deserves better."

Munson, who serves as Liberal whip in the Senate, said in his opinion Fairbairn understood the content of the legislation she voted on. He said suggestions the party kept her on to preserve her Senate seat are without merit.

"From my perspective, with the Conservative majority, one vote would not make a difference, but Senator Fairbairn's vote made a difference to me," Munson said.

"She was well briefed, ready to vote, and knew what she was doing."

Sen. Mobina Jaffer said a health decline was noticeable during the budget vote in June.

“I knew she was asking some more questions of me, so I knew there was something not quite right,” Jaffer told CTV News.

Lethbridge Regional Police Chief Tom McKenzie, a long-time friend, said Fairbairn seemed confused at times as she led a guided tour of the Parliament Buildings after-hours back in May.

However, she “was well informed and we discussed a few things about certain bills and certain things that were happening,” he told The Canadian Press.

Despite the support, others are calling for Fairbairn to step down.

Greg Thomas of the Canadian Taxpayers Federation said that although the senator’s illness is “tragic… she should resign, the Senate should clear the seat.”

Fairbairn is a former journalist who worked in the office of former prime minister Pierre Trudeau for 14 years. She was appointed to the Senate in 1984.

With files from The Canadian Press and a report from CTV’s Richard Madan