A World of Warcraft player spent an average of 21 hours per day playing the online game.
The gamer was logged into social networking client Raptr while playing, which tracked their stats.
Raptr found the user poured 149 hours into playing World of Warcraft during Cataclysm's first week on sale, although it's possible the user was logged in for some of those hours but away from the computer.
Other statistics showed that the most connected 11 per cent of gamers generated over half of all hours spent playing the game.
Eurogamer also reports that the average total playtime per user on day one of Cataclysm was around six hours and 15 minutes. The average World of Warcraft game session now stands at just over two hours.
The news comes following BBC's Panorama documentary on games addiction, which focused on several World of Warcraft players.
World of Warcraft: Cataclysm is the third expansion pack for Blizzard Entertainment's MMO RPG. It was released on December 7th and shifted 3.3m copies within its first day on sale, making it the fastest-selling PC game of all time.
Last week Blizzard teased a next-gen MMO codenamed Titan.