In many older studies, long-standing inflammation of the pancreas was most often due to alcohol - but in the U.S. at least that pattern is changing, a new study shows.
Smoking and genetic factors may be replacing alcohol as the major cause of the condition, researchers say.
Long-term inflammation of the pancreas, known medically as chronic pancreatitis, occurs in 15 to 20 out of every 100,000 people in the United States. Patients usually suffer from abdominal pain and don't digest food properly. There is no cure, and treatments are aimed at managing the pain and preventing poor nutrition.
In a nationwide investigation, researchers found that out of every 10 cases, alcohol caused four, instead of six to nine as was previously estimated.
Using information on patients with a chronically inflamed pancreas from 20 major medical centers, the research team found that about three of every 10 cases were due to genetic diseases, disorders of the immune system, physical damage, and other factors.
In another three of 10 cases, doctors could not find a cause.
Dr. Greg Cote, a professor at the Indiana University School of Medicine and the lead author on the study, told Reuters Health he wasn't surprised to find so many patients whose long-term pancreas inflammation couldn't be explained.
"It's not uncommon to work them up and down with diagnostics and imaging and, at the end of the day, not find the cause," he said.
Cote suspects that many patients in the mystery-cause group may have developed pancreatitis from smoking.
This group tended to have higher than average rates of smoking, he and his colleagues report in the journal Clinical Gastroenterology and Hepatology. And earlier studies have found that smoking increases the risk of an inflamed pancreas.
In an editorial published along with the study, Dr. Albert Lowenfels, a professor at New York Medical College, writes, "This is an important finding because we now know that smoking, along with alcohol, is another major avoidable lifestyle factor leading to this burdensome disease."
"I think smoking is clearly the single biggest environmental factor, but I think genetics is going to play a big role as well," Cote said.
He pointed out that in Europe too, recent studies show the proportion of alcohol-related cases is shrinking. His is the largest study to look at the causes of chronic pancreas inflammation in the U.S., he said.
The researchers say their next step is to try to identify genes that may be responsible for cases with unknown causes.
Cote's study, funded by the National Institutes of Health, the National Pancreas Foundation, and several private donors, included 539 people with chronic pancreatitis.
One of the limitations of the study is that all of the patients were treated at medical centers attached to universities, which tend to care for more sick patients and perhaps receive more cases with unknown causes.
Cote said there may be alternative causes even among those patients whose drinking is thought to be the cause of their pancreatitis.
His study found that about one third of patients with alcohol-caused pancreatitis did not meet the criteria for drinking heavily enough to cause damage to the pancreas.
"I think it exemplifies that there are many unknowns" to this disease, Cote said.