The Aston Villa boss, who had major heart surgery in 2001 when he was in charge of Liverpool, is back in hospital after being admitted with chest pains in midweek.
But, despite almost total job security with Manchester United and an unprecedented era of success at Old Trafford, Ferguson revealed that he often worries whether the stress of the job is getting to him or simply old age catching up as he approaches his 70th birthday.
Feeling the strain: Gerard Houllier took ill with chest pains in midweek
The United boss, who took charge of Scotland in the 1986 World Cup after witnessing Jock Stein's fatal heart attack in the dug-out at Cardiff a year earlier, had a pacemaker fitted in March 2004 after he was diagnosed with an irregular heartbeat.
He said: 'Some mornings I wake up with aches and pains and I worry what it is. I sometimes tell my doctor I've got a pain here and a pain there and he says, 'it's your age, you're growing old'.
'That's what happens. You hope you can keep your health. Modern nutrition and lifestyle mean people live longer, but it doesn't guarantee complete health all your life.
'I had a pacemaker put in seven years ago. That was the first indication that your body is not working the same as 20 years ago.
'You have to pay attention to your health when you get older. It doesn't come without penalties.'
Ferguson and Houllier are by no means the only high-profile managerial figures to suffer heart problems. Graeme Souness and Joe Kinnear both underwent major surgery, while Sam Allardyce had an angioplasty to insert a stent in an artery that had narrowed.
Under the knife: Graeme Souness (left) and Sam Allardyce (right) both had heart surgery
A study by one of the world's leading cardiovascular experts in 2005 estimated that almost half of English football managers will experience 'significant' heart problems during their course of their careers, with Dario Gradi and Barry Fry two more well-known figures who needed treatment.
However, asked if there are more stressful occupations than football, Ferguson said: 'Yes, I'm sure there is. It's about dealing with stress.
'Sometimes people feel pressure getting an electricity bill. It depends on what state of life you are in and what your conditions in life are. Dealing with stress is always there for everyone in different ways. How you deal with it does make a difference.'
Ferguson has had every reason to feel stressed this week after United's Treble hopes were wrecked by their FA Cup semi-final defeat to Manchester City, and a goalless draw at Newcastle allowed champions Chelsea to close to within six points of the Premier League leaders.
United have to face both Chelsea and third-placed Arsenal in the next fortnight, but Ferguson is confident his players can hold on to reclaim the title with just five League games remaining.
Fighting fit: Sir Alex Ferguson is still going strong as he approaches his 70th birthday
As he prepared for Saturday's lunchtime kick-off at home to Everton, Ferguson said:
'If we win, there's only four games left and a minimum six-point lead. That's the way to look at it. You run out of games eventually, so I'm not looking beyond tomorrow.'
Everton have not won at Old Trafford since their first Premier League visit there in 1992, but David Moyes's side stunned United by scoring twice in injury-time to snatch a 3-3 draw at Goodison Park earlier this season and have the best form in the top-flight over the last nine games.
'They are never easy games against Everton because it's a local derby in a way,' said Ferguson. 'But our home record has been really good this season. The performance levels have been fantastic and hopefully we can continue that.'
Ferguson also confirmed that Darren Fletcher has almost recovered from a debilitating stomach virus and could be fit to return in time for the second leg of United's Champions League semi-final at home to Schalke and the Chelsea clash.
?Timely boost for Houllier as Villa boss discovers he does not need surgery Houllier's Aston Villa job in doubt as Frenchman suffers fresh health scareAll the latest Aston Villa news, features and opinionAll the latest Manchester United news, features and opinion
?Explore more:People: Alex Ferguson, Darren Fletcher, Graeme Souness, David Moyes, Joe Kinnear, Sam Allardyce, Gerard Houllier Places: Newcastle, Cardiff, Liverpool, Scotland
Source: Daily Mail
Source: Daily Mail