Loss is much more general. It can refer to things 'I lost my ball'. When it is used for skills or abilities, it would be used for complete loss: 'He lost his sight at a young age'. Impairment only refers to a skill or ability, and usually refers to partial loss. 'His hearing was impaired after the accident'. 'Taking anti-depressants may lead to an impairment of sexual function'.

'Impairment' means damage. So, if someone has impaired sight or hearing, for example, they cannot see or hear very well. 'Loss' may suggest total loss.

Cited from Oxford dictionary

impair: Weaken or damage (something, especially a faculty or function): synonym: damage, harm, diminish, reduce, weaken, lessen, decrease, blunt, impede, hinder, mar, spoil, disable; example sentence: Driving in an intoxicated state makes a person prone to accidents as alcohol impairs judgement and slows reflexes. loss: The fact or process of losing something or someone: synonym: mislaying, misplacement, dropping, forgetting, overlooking example sentence: They have admitted the financial crisis could mean more job losses and ward closures.

Impairment refers to something not functioning on its' proper level. My car was impaired by havinga deflated tire. Loss is just losing something, showing a lack of something, or a negative result in a sports game. We lost to the Yankees. I lost my shoe. I feel lost. I had a feeling of loss when I realized the car wouldn't start, because its' engine is IMPAIRED. I