His son Philip made the revelation on their local radio station Shannonside after his dad was too ill to attend events in London to mark the 20th anniversary of the Downing Street Declaration.
The Irish Independent reports that Philip told the station that his 81-year-old father’s inability to attend was a measure of the deterioration in his condition.
His mother Kathleen represented the former Taoiseach (Irish PM) at the event alongside former British Prime Minister John Major and the former Irish Minister for Foreign Affairs Dick Spring.
The Downing Street Declaration is widely regarded as Reynolds’ biggest achievement in office.
Son Philip revealed: “Right now he’s pretty bad. He has 24-hour care. A sure sign of that is when you see that my mum was representing him last week.
“It was difficult to get my mum to come to the Temperance Hall or the Mall in Longford when he was elected.
“To get her to go out front and represent him says everything about how he is himself. If he had been any way well enough, he would, of course, have been there.”
Philip revealed that his dad first showed signs of suffering from Alzheimer’s disease five years ago when he began to repeat himself and ask the same questions ‘over and over again.’
He added that the disease has ‘progressed a long way since then.’
He added: “He might give the impression that he knew who people were when they came to visit, he wouldn’t remember who the person was afterwards.
“Maybe in the quiet of the evening he does. Mum goes in and spends a lot of time with him and sits and watches the 9pm news with him. Maybe he does remember for mum’s sake, because it is pretty sad.”
Reynolds' son also told how the onset of the illness has affected people’s perception of the former politician.
He said: “People thought Dad was trying to dodge something [at the time of the Mahon tribunal] but he was actually in early stages of Alzheimer’s”.
“He went from being someone people wanted to meet to being a nuisance to some people.”