Query with order by causing performance issue

Hi,

We have a list page containing 12 fields and the users are allowed to sort the list page using these 12 fields.
I already created index for the corresponding list query and the same is performing well. But when the user apply sort for any of the field its is impacting the performance of the list query. Is there anyway to create index for sort by for these 12 fields?

Thanks,
Siju.

There is no easy way to do. If need to do sort it must produce all possible values and do sort.