The reduction in performance on these tasks associated with a 25-decibel hearing loss (classified as "mild") was equivalent to an ageing effect of seven years in cognitive abilities.

BBC: Viewpoint: Does deafness contribute to dementia?

If so, following them over the years also picks up the happiness effect of ageing - which we might falsely attribute to marriage.

BBC: Why it's hard to measure happiness

Ill-designed pension systems magnify the effect of population ageing by creating incentives for people to retire ever earlier.

ECONOMIST: Time to grow up | The