Vestar Capital Partners has completed a strategic growth investment in Nox Health, according to a news release. 

Nox, based in Alpharetta, Ga., is a global sleep health company. Founded in 2007, the company provides technology and program solutions to help diagnose and manage sleep problems.

Vestar Capital Partners, based in New York, is a private equity firm focused on middle market companies. Founded in 1988, the firm prefers to make more substantial investments from a dollars perspective in businesses from a few sectors, including healthcare.

Terms of the investment were not disclosed.