While more Massachusetts residents are insured now, many still struggle to keep up with health care costs, according to two new reports released Thursday.

A poll by The Boston Globe and the Blue Cross Blue Shield found that 97 percent of adults in Massachusetts have health insurance, but even with coverage many have trouble paying health care bills. One-third of those polled said the cost of care remains their biggest health concern.

Thirteen percent of insured residents said they were unable to pay for some kind of health service or fill at least one prescription in the past year.

The telephone poll of 506 adults was conducted earlier this month by the University of New Hampshire Survey Center. It has a margin of error of plus or minus 4.4 percentage points.

A study also released Thursday found the cost of health care plans offered to workers rose faster than their income.

Families USA, a Washington DC-based advocacy group looked at census data and information from the federal departments of labor and health and human services.

The study found that while annual health insurance premiums rose from $7,341 to $13,040 between 2000 and 2007 - an increase of 77.6 percent - the median earnings of Massachusetts' workers rose from $30,964 to $34,542, an increase of 11.6 percent.

The percentage of insured in Massachusetts far exceeds the national average because of a first-in-the-nation law requiring residents to have insurance. But experts say hefty deductibles and co-payments still make it difficult for many families to afford care. (AP)