As the average life expectancy is about 80 years old in the UK and US the reality is that once over 40 you are middle-aged whether you will admit it or not. For those with offspring it may well be when your kids leave home that's the time of life marker for you.
Here's when you start worrying about where your life is going and feeling trapped and invisible. Old forgotten dreams resurface in some unexpected and even unwelcome ways.
Men and women deal with the fear of tipping over the halfway point of life in different ways. While a man may buy a sports car (red, of course) or a motorbike, or trade the wife in for a younger girlfriend, women tend to choose travel or an 'all singing all dancing' food processor.
When you are younger it's all about how many hours in the day but as you get older it has to be about how much you can personally do with the energy available each day. Sure, you may well be awake from 7am to midnight every day but that doesn't mean you will have the energy to work for all your waking hours nor should you. It is perfectly acceptable to factor in 'down time' and to not want to work until bedtime.
Is knowing you are getting older when you accept you can't drink and go dancing like the old days, not least because there are kids half your age looking at you as if you're an alien/their grandparents? It's OK to not want to party late into the night as you know you will suffer more for it the next day than you ever did when younger. Meeting a friend at lunchtime can be the answer to know you won't be going out that night and be too shattered by then.
Apparently if you listen to talk radio shows instead of music and start regularly feeding the birds in the garden then you have reached middle-age. If you find yourself wistfully referring to the 'old days' too often and change your favourite tipple to sherry then the signs are there for all to see. If golf becomes your main form of exercise and you forget people's names but they let you get away with it then yes, start accepting. I thought failing eyesight should be on the list but others tell me failing hearing is causing them more concerns.
It's not all negative as the ability to accept and to not fight reality is one of the better factors of aging.
Go on, be honest. Will you deny middle-age has arrived right up till the time old age hits?