See if they can crack a joke,

Literally ,if they can their  airway is patent, their breathing intact and they are perfusing their brain enough to perform a complex task-humour.
Airway, Breathing, Circulation, Disability in medicine

Metaphorically speaking, most people in the rat race don’t laugh, smile or crack jokes.

so slowly dying anyway because they are not really living,

and living involves emotion and humanity, for everything else  there’s MasterCard, money or greed.

stuff that paradoxically causes most  of our headaches

Be happy