Zhang Xinyan tries on a hotel in Beijing, Dec 13, 2013. [Photo/IC]

To date, Wu has slept in and reviewed 400 hotels, including some overseas. Half of them are five-star hotels.

Some hotels have welcomed his advice. He said the Sheraton Hotel in Chuzhou in east China's Anhui Province rearranged the lamps in guest rooms based on his recommendations.

Qunar reimburses hotel expenses, but does not give its sleep testers additional pay. However, Wu started a public WeChat account last February, and his popularity as a reviewer has earned him nearly 40,000 subscribers. The account has generated perks and profits as hotels often seek him out for advertising partnerships. He did not say how much he makes through WeChat, only disclosing that he has earned many hotel coupons.

In addition to five-star hotels, customer demand has driven sleep testers to review more boutique hotels, which serve a wider range of clients and have more favorable prices.

Tang Xiangdong, director of the sleep medical research center of West China Hospital of Sichuan University, said stress and poor sleep and eating habits are behind many sleeping problems.

The center treated 20,000 patients last year, 60 percent of whom suffered from sleeplessness.

Tang said more and more young people are suffering from sleeping problems. The youngest patient they treated was an 11-year-old girl who was under pressure to study from her parents.

"Emerging services such as sleep testers show the growing public demand for quality sleep, especially from young people," he said.