Unfit in middle age

After accounting for other factors (including socio-economic status, a number of long-term conditions, smoking, alcohol and BMI), researchers found men between the ages of 37 and 45 were over two-and-a-half times more likely to die than non-frail people of the same age.

The figures were similar in all the other age groups (45-55, 55-65, and 65-73).

Similar associations were found in women who were judged to be frail and were 45 or older.

Frail people were also far more likely to have conditions such as multiple sclerosis and chronic fatigue syndrome.

Lead author of the study, Prof Frances Mair, from the University of Glasgow, said the findings suggested there was a need to both identify and treat frailty much earlier in life.

So what can we do?

Dr Peter Hanlon, a co-author on the frailty study, said the good news is that frailty might be reversible in people, particularly if it is identified early.

The key for those who are unfit in middle age is making healthy changes "as soon as possible", says Ilaria Bellantuono, professor of musculoskeletal ageing at the University of Sheffield.

"The key is a healthy diet and exercise. It's the only thing we know that works," she says.

Losing weight, stopping smoking, cutting back on alcohol, exercising regularly and eating less salt are just some of the things you can do to lower your blood pressure.

And similar advice applies to reducing your risk of dementia and helping to keep your brain healthy as you age, says Dr Laura Phipps from Alzheimer's Research UK.

But the million pound question is how do you get people to change their habits?

Prof Bellantuono said that for some, health warnings won't be enough.

Instead, finding an "internal motive that speaks to them" will be key to getting some people to exercise and be healthier.

"That could be picking up the grandchildren or going to watch the football," she adds.