How old are you Billy? What are 40-50 year olds like in your area?
In my area they are perfectly able to do a day's work, go out in the evening, play physically with kids, take them out all day, look after them at night. They listen to mainstream radio, have sky and netflix (i.e. aren't embarrassingly out of touch with modern music and media) wear clothes from Dorothy Perkins and Debenhams not Topshop maybe but are by no means in M&S classics. Most have teenage kids and are just fine, some have primary age kids and are just fine.
Where is this place where you can spot over 40s a mile off and they're 'granny' type figures?!?
Life expectancy too - how long do people live in your area? If they're hitting late 70s-80s, they'll be just fine in their 40s mostly.
As for the health issues: please enlighten me as to what you've read about these, what books and reputable reports (not the daily mail website).
I have no rose tinted specs: I've been living with a condition which makes pregnancy dangerous all my life ... so have read up on it, spoken to consultants etc'. The chance of miscarriage, some disabilities and blood pressure issues slightly rises after about the age of 35-38 depending on each woman's overall health: but if they have healthy eggs they are considered perfectly able to have children in a normal way and not 'high risk' until about 43, whereupon they have extra monitoring as they are fine in most cases.
In my case, my pre-existing condition was almost swept after the carpet because I was over 30 (i.e. once i hit 30 they could say 'age' and ignore that I'd had symptoms for years), thankfully trained medical professionals knew better and got me a treatment plan. My health is likely to be better over the next 20 years than it was for the last 10.
That's not a new thing: a similar thing happened to my grandmother and many people injured in WW2. As they recovered, they became stronger in their 30s-40s.
Of course, some people do just eat pizza and smoke fags on the sofa and are weak by 35. But that's not just their age.