UPDATE 1-Cigna tops profit estimate, gives upbeat 2018 forecast

(Adds details on forecast)

Feb 1 (Reuters) - Health insurer Cigna Corp reported a better-than-expected quarterly profit on Thursday, helped by higher enrollment and it forecast 2018 earnings above Wall Street estimates.

Cigna joined other health insurers, such as UnitedHealth and Anthem, in reporting a strong quarter and an upbeat forecast thanks to the recent U.S. tax changes.

Cigna's membership at the end of 2017 totaled 15.9 million, an increase of more than 700,000 customers during the year, driven by strong growth across commercial market units.

The company focuses on large and medium-sized corporate healthcare and sells international insurance as well as government-backed Medicare plans.

Cigna said it expects adjusted income of $12.40-$12.90 per share in 2018, ahead of analysts' estimate of $12.20, according to Thomson Reuters I/B/E/S.

However, net income fell to $266 million, or $1.07 per share, in the fourth quarter ended Dec. 31, from $382 million, or $1.47 per share, a year earlier.

Excluding items, the company earned $1.94 per share, beating analysts' average estimate of $1.89.

Operating revenue increased 6 percent to $10.51 billion, just above analysts' estimate of $10.31 billion. (Reporting by Ankur Banerjee in Bengaluru; Editing by Martina D'Couto)