In a survey of an infantry brigade that had recently returned from Afghanistan, 44% of soldiers reported having been in pain for at least three months, and 15% had used opioids during the past month.
By comparison, researchers estimate than 26% of civilians live with chronic pain and 4% use opioids.
"We were surprised by the percentages," said Robin Toblin, a psychologist at the Walter Reed Institute of Research and lead author of the study, published Monday in the journal JAMA Internal Medicine.
Experts said the study suggested that, despite the military's efforts to improve pain management — a growing concern during the course of the recent wars — more needs to be done. It also raised but did not answer questions about whether opioids were being prescribed properly.
Dr. Mark Edlund, a psychiatrist and pain expert at RTI International, a North Carolina nonprofit research group, said the study gave no indication that painkillers are being used any differently in the military than they are in other health systems.
"American medicine in general is overprescribing," said Edlund, who was not involved in the study.
A rapid rise in the use of prescription opioids such as oxycodone and hydrocodone has been a growing public health concern as the number of overdose deaths and rates of addiction skyrocket. More than 16,000 people a year die of overdoses, quadruple the number in 1999.
The drugs are effective for moderate and severe short-term pain. While they are often used for chronic pain, there is little evidence that the benefits outweigh the risks.
The Army researchers surveyed 2,597 soldiers three months after their brigade returned from Afghanistan. A small number had been deployed to Iraq. Combat injuries were the biggest risk factor for chronic pain.
Among the 1,131 soldiers reporting chronic pain, nearly half described it as mild, and nearly 14% said it was severe.
Most patients with chronic pain were taking over-the-counter medications. Fewer than a quarter — or 259 —had a prescription for opioids. Most of those said they had used opioids a "few or several days" during the past month, while 60 soldiers had taken them nearly every day.
One finding raised the possibility that the drugs were being used unnecessarily, researchers found. Among soldiers who reported taking opioids in the last month, 17 said they had no pain and 144 described their pain as "mild."
In most of those cases, soldiers had used the drugs for fewer than half the days over the last month, the researchers said.
Rates of chronic pain were significantly higher in soldiers suffering from post-traumatic stress disorder and depression, though those patients were no more likely to use opioids.
Edlund said that data on opioid dosages and prescribing patterns are needed to evaluate the military's use of the drugs.
"You need to characterize this use in a lot greater detail before you can say it's misuse," said Edlund, who testified before a Senate committee in April on prescribing patterns in the Department of Veterans Affairs health system.
His analysis showed that, among patients with chronic pain that is not related to cancer, just over half receive an opioid prescription each year — about the same rate as patients in other healthcare systems. The dosages are lower in the VA system, though the number of days patients take the drugs — 120 days a year on average — is higher.
Veterans of the wars in Afghanistan and Iraq were less likely than other VA patients to be prescribed opioids.
For its part, the
In a commentary that accompanied the new study, Dr. Wayne Jonas, an expert on chronic pain, and Dr. Eric Schoomaker, a former surgeon general of the Army, said that, without improvements in pain management, many service members are at risk of increasing disability throughout their lives.
"Chronic pain and use of opioids carry the risk of functional impairment of America's fighting force," they wrote.