WASHINGTON - Nearly a third of Americans experience long-lasting pain - the kind that lingers for weeks to months - and too often feel stigma rather than relief from a health care system poorly prepared to treat them, the Institute of Medicine said Wednesday.

The staggering tab: Chronic pain is costing the nation at least $558 billion a year in medical bills, sick days and lost productivity, the report found. That's more than the cost of heart disease, the No. 1 killer.

All kinds of ailments can trigger lingering pain, from arthritis to cancer, spine problems to digestive disorders, injuries to surgery. Sometimes, chronic pain can be a disease all its own, the report stressed.

Whatever the cause, effective pain management is "a moral imperative," the report concludes, urging the government, medical groups and insurers to take a series of steps to transform the field.

"We're viewing this as a critical issue for the United States," said Dr. Philip Pizzo, Stanford University's dean of medicine, who chaired the months-long probe.

For too long, doctors and society alike have viewed pain "with some prejudice, a lot of judgment and unfortunately not a lot of informed fact," he said.

The toll isn't surprising, said Dr. Doris K. Cope, pain chief at the University of Pittsburgh Medical Center, who paused between patients Wednesday to read the report. The population's getting older and less fit, and more survivors of diseases like cancer live for many years with side effects from treatments that saved them.

Too many patients think a pill's the answer, she said, when there are multiple different ways to address pain including physical therapy, stress reduction, weight loss, and teaching coping skills. Patients who take control of their pain fare better, but too many have unrealistic expectations.

"Pain is not simple," Cope said. "We as physicians need to be healers and educators as well as technicians. We certainly don't want to be pill mills."

Doctors do worry about overprescribing narcotic painkillers, and law enforcement steps to fight the serious problem of prescription drug abuse can be one barrier to pain care. But the institute countered that it's far more likely for a pain patient to get inadequate care than for a drug-seeker to walk out with an inappropriate prescription. While newer, better medicines are needed, those narcotic painkillers are a safe and effective option for the right patient, the report said.

But barriers to good care extend far beyond that issue, said the panel, which analyzed research and the reports of more than 2,000 patients and caregivers about pain's toll.

Because pain can't be seen like bleeding, or felt like a lump, or X-rayed like a broken bone, or heard like a skipped heartbeat, health workers who wrongly believe the intensity of pain should correlate to a specific medical finding may diminish or even dismiss a patient's complaint, the report found.

In fact, pain is highly subjective. Two people with the same injury may feel different degrees of pain depending on genetic factors that affect pain tolerance, what other illnesses they have, stress or depression, and even whether they feel support or criticism from health workers or their families.

Care must be tailored to each patient. Yet too few doctors are trained in its management, the report said, citing a study that found stand-alone pain courses aren't required in most medical schools. Also, insurance may not cover time-consuming counseling in pain-management techniques, consultations with specialists or even non-drug care.

Pizzo called the finances sometimes perverse: Some insurance pays for an operation for low back pain but not much cheaper and often more effective physical therapy.

And prompt care for acute pain, like that from surgery or a broken bone, is important as well. Serious pain that isn't properly treated sometimes can hijack the nervous system and essentially rewire it for pain - leaving misery after the condition that caused the initial pain is resolved.

The report concluded at least 116 million adults suffer long-lasting pain, consistent with some previous estimates, but couldn't say how many cases are severe or disabling.

The economic costs, however, are sure to attract attention in Congress, which mandated the report as part of the new health care law. The report found health care for pain costs $261 billion to $300 billion a year, while lost productivity adds another $297 billion to $336 billion. The federal Medicare program accounts for a quarter of those health bills.

Among the report's recommendations:

• Health providers should perform and document formal pain assessments of patients, a step toward proper treatment.

• Medicare, Medicaid, workers' compensation programs and private health plans should cover individualized pain care.

• Pain specialty groups should create collaborations with primary care doctors to improve patient care and counseling.

• The government and health organizations should better educate patients and the public about pain, to help eliminate stigma.

• The National Institutes of Health should increase pain research, including designating one of its centers as the lead institute for pain.

• Training programs for doctors, nurses, dentists and other health professionals should include pain education.

• By the end of next year, the Health and Human Services Department should create a strategy for dealing with pain as a public health problem and reducing barriers to care.