I used to work for a large Government agency and when a colleague (who was about 58) left on an early release scheme his boss (an ambitious younger person in their late 30s) actually said out loud , "Oh I wish we could plug a USB stick into your brain, to download all your knowledge."
Life expectancy has plateaued and for women is beginning to reduce (as a result of ill health) but it appears that the study assumes this to be temporary.
Incidentally, you can check your average life expectancy here.
The main issue in this study is increasing poor health which is related to...