There is no official confirmation till now but as per Publication in the Gazette of India, there would upper age limit in NEET 2018 and NIOS students are not eligible but nothing can be said without the official declaration so lets wait for the same.

To know more about the same, you can go through the below link -

https://medicine.careers360.com/news/neet-2018-gazette-of-india-reveals-nios-students-ineligible-upper-age-limit-reintroduced-358242

Good Luck!!!