Mr Cadogan told the Otago Daily Times yesterday he had been reluctant to reveal the events, which he described as resembling heart attacks, until he was interviewed recently about Invercargill Mayor Nobby Clark's open-heart surgery.
"My instinct is just to knuckle down and carry on, which is something I picked up from my mother, who lived with severe medical issues but refused to be cowed by them.
"I've realised lately though that it's fine to be a fool unto myself, but the situation is taking an unacceptable toll on my wife and family, and it's not fair to be a fool to them. So if I have another serious incident, as much as it pains me to leave a job unfinished, I'll be stepping down for their sake," Mr Cadogan said.
The 64-year-old said he had the first attack in October last year, followed by three further incidents, the last in April, each requiring brief hospitalisation.
Although the pressures of "unprecedented" challenges facing local government — particularly Three Waters — had been a contributing factor, the former shearer said a long-standing health problem was the main culprit.
"I've had diabetes for the past 28 years, and the doctors tell you it will always eventually affect your heart.
"I've managed it pretty well with insulin for the past 25 years, but now it's getting to the pointy end of things."
Despite the seriousness of the situation, Mr Cadogan said he was not heading for the changing rooms just yet.
"We've been in such a fight for Three Waters for so long, it's like we have the final 10 minutes to go in a game and we're three points down. There's no way I'm walking off the paddock — it's time to dig in."
Local government had changed unrecognisably since he entered politics in 1998.
"Back then, we'd sit around the table with a cup of tea for a couple of hours and make agreeable decisions about civic beautification.
"During the recent long-term planning process, councillors had to wade through 2700 pages, and a total of six days of vigorous hearings and debate, while overseeing a $1.4 billion organisation. It's a different beast altogether."
Despite the challenges, he still regarded it as a "privilege" to work on behalf of ratepayers.
"I've had to wind back my hours from maybe 80 a week to 60, but fighting on behalf of the ratepayer is as dear to my heart today as it was at the outset", he said.
"Day after day of unrelenting pressure doesn't come without its toll for all on council, but it's a fight we remain committed to 100%."
As well as the reduction in hours, Mr Cadogan said he was managing his health with regular "nana naps".
"The attacks have led to quite a bit of tiredness, but a half-hour nap and I'm good to go again."
He said the situation had also led to his appreciating "the good things" more.
"We've helped 800 locals into work since I became mayor in 2004.
"I'm lucky to have a supportive council and staff, and medical professionals locally and in Dunedin have been first class.
"There's still so much more to do, so I'm more motivated than ever to get things over the line while I can."
