Factory activity slowed more than expected in the U.S. Mid-Atlantic region in January, paring expectations of manufacturing's role in helping a U.S. economic recovery, a survey showed on Thursday.

The Philadelphia Federal Reserve Bank said its business activity index slipped to 15.2 from 22.5 in December, which was a 4-1/2-year high.

Analysts polled by Reuters had expected a January reading of 18.0.

Any reading above zero indicates growth in the region's manufacturing sector.

The survey covers factories in a region encompassing eastern Pennsylvania, southern New Jersey and Delaware and is looked at closely as one of the first indicators of the health of the U.S. manufacturing sector.

(Reporting by Richard Leong; Editing by James Dalgleish)