the national health insurance subscribers

[rainous]

We are servicing obligatory medical examination to the national health insurance subscribers.

Is "the" necessary in the sentence? If so, would you please explain to me why?

Thanks

[5jj]

No. It is incorrect, unless previous context makes it appropriate.

[rainous]

Thank you.

I have one more question regarding the article.

"...research into hearing impairment..." is a phrase I found on Google.

Shouldn't "hearing impairment" either have an article in front of it (maybe "the"?) or be changed to a plural form like "hearing impairments"?

[5jj]

Thank you.

I have one more question regarding the article.

"...research into hearing impairment..." is a phrase I found on Google.

Shouldn't "hearing impairment" either have an article in front of it (maybe "the"?) or be changed to a plural form like "hearing impairments"?

No. The word is used uncountably.here.

[rainous]

No. The word is used uncountably.here.

Is it OK to use a word either countably or uncountably at my discretion?

As for the example I gave:

"Research into hearing impairment"

"Research into hearing impairments"

Are they both correct or the second one isn't?

[5jj]

Is it OK to use a word either countably or uncountably at my discretion? Well, it does depend on the intended meaning. [...]

1. "Research into hearing impairment"
2. "Research into hearing impairments"

#1 suggests research into the state of impaired hearing.
#2 suggests research into various conditions/diseases that bring about impaired hearing.