BOSTON -- The Massachusetts Medical Society says the state's doctors are under increasing pressure from a series of factors, a trend that could undermine patient care.

The doctor's group report released Tuesday cited four major concerns, including growing medical malpractice insurance rates and the increased use of emergency rooms by patients, which was up 3.5 percent in 2009.

Nationally, emergency room visits rose 2.8 percent.

The group also pointed to the increased cost of maintaining a doctor's office and an aging physician work force. The percentage of Massachusetts physicians older than 55 rose 3.2 percent in 2009, compared to a national increase of 2.6 percent.

The cost of maintaining a doctor's office rose 3 percent in Massachusetts last year while it declined nationally by 1.3 percent.

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Online:

Massachusetts Medical Society: http://www.massmed.org