Yes, IMPAIRMENT is a Scrabble word!

Letter values in Scrabble US: I 1, M 3, P 3, A 1, I 1, R 1, M 3, E 1, N 1, T 1.

Is it a valid word?

IMPAIRMENT is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the occurrence of a change for the worse
a symptom of reduced quality or strength
the condition of being unable to perform as a consequence of physical or mental unfitness
damage that results in a reduction of strength or quality
the act of making something futile and useless (as by routine)