Windsor, who was made a Dame in 2015 for services to drama, is famous for her roles in nine Carry On films and as pub landlord Peggy Mitchell in EastEnders.
He stressed that revealing the news any earlier would have been detrimental to her health.
"Stigma around dementia still exists, and many people are facing it in the shadows".
"So rather than me living in fear she might get confused or upset, they'll know that if her behaviour seems odd, it's due to Alzheimer's and accept it for what it is". She has now retired from charity work as well as acting.
Speaking with the Sun, he said that the Carry On movie star had wept when she was diagnosed with the disease: 'When the doctor told us, she began crying then held it back, stretched her hand out to me and mouthed, "I'm so sorry"'.
Pam, a close friend of Barbara's, who played Pat Butcher alongside Barbara's Peggy Mitchel in EastEnders for many years, revealed that she had not been expecting Scott's announcement about his wife's health.
Speaking to The Sun, Mitchell said the following: "Since her 80th birthday last August, a definite continual confusion has set in, so it's becoming a lot more hard for us to hide".
Tim Parry, director of Alzheimer's Research UK, also praised the decision to go public.More news: Egypt follows with great concern developments of U.S. withdrawal from Iran deal
"Alzheimer's is the most common disease behind dementia, accounting for around two thirds of cases of the condition in older people", he said.
"It's important to bring the disease out into the open as a crucial step towards us tackling it".
Speaking to the Sun, Mitchell said that Windsor's symptoms had worsened in recent weeks, with the actress suffering from memory loss and confusion.
"I didn't want someone else to dictate how or when the diagnosis came out, so that's why I'm speaking about it now".
At first I was frustrated when my granny would ask for the fifth time that morning whether she had RSVPed to my wedding.
"Scott was adamant he didn't want that coming out", Ms Moore said.
"It was a release but he felt so guilty because he felt he couldn't protect her any more".
A small circle of friends who had begun to notice her occasional confusion were told shortly after the diagnosis, he said. Whenever they went out, the public were like moths to a flame with Barbara and she loves them.
His associates included the gangster Reggie Kray and his brother Charles, with whom Dame Barbara had relationships.