Face and neck pain were the most common locations for persistent pain, though more than any condition or specific region of the body, persistent pain was associated with disability. Adults who couldn’t work because of a disability reported pain most often, with 60 percent of them experiencing it most days or every day.

Some other findings are about what you’d expect—people who rated their overall health as “fair” or “poor” were more likely to have pain, as were obese people and people who’d recently been to the hospital. And living with persistent pain was associated with higher rates of anxiety, depression, and fatigue.

The researchers point out that their estimate that 39 million adults in the U.S. have persistent pain is much lower than that of a 2011 report by the Institute of Medicine that estimated 100 million Americans with chronic pain. The study suggests the difference is in the definition—“persistence can be seen as a relatively discrete component of the broader construct of chronicity,” the researchers write.

They also acknowledge the difficulty of even studying pain at all, subjective as it is: “A single population survey item cannot hope to capture the complexity of the pain experience,” the study reads. But the researchers suggest that persistence could be one piece of the pain puzzle, and now we know some risk factors for it.