Long-term, consistent use of acetaminophen is associated with slightly increased risk of certain blood cancers, according to researchers at the Fred Hutchinson Cancer Research Center in Seattle.
What isn't clear is whether the painkiller, best known as Tylenol, is responsible for the increased risk or if those who use it are also more likely to have medical issues that might be associated with the cancers. No such increased association of blood cancers was found with increased use of aspirin, non-aspirin non-steroidal anti-inflammatory drugs (NSAIDs) or ibuprofen.
The study by University of Washington researchers just published in the Journal of Clinical Oncology looked at 64,839 people ages 50 to 76 years who were recruited from 2000 to 2002 for the Vitamin and Lifestyles study. Earlier research had returned "inconsistent" results for NSAIDS, but suggested an increased risk with acetaminophen (called paracetamol in Europe). The abstract described the new work as a "large prospective cohort study to examine these associations."
Acetaminophen is a pain reliever and a fever reducer. Using too much of it has been associated with liver damage and even death. Notes information at Drugs.com, it's also dangerous to use with alcohol, or by someone with a history of alcohol use. Another of the often-reported overdose dangers occurs because acetaminophen is frequently one of the ingredients in other over-the-counter products, so someone taking Tylenol, for instance, who also is using a cold medication might experience an overdose and organ damage. It's important to read labels to see which ingredients a product contains.
After they adjusted for age, sex, race/ethnicity, education, smoking, self-rated health, arthritis, chronic muskuloskeletal pain, migraines, headaches, fatigue and family history of leukemia/lymphoma, the Washington researchers found an almost two-fold increased risk with "high use" of the medication, which they defined as four or more times a week for four or more years. The association was seen for myeloid neoplasms, non-Hodgkins lymphomas and plasma cell disorders. It was not seen for chronic lymphocytic leukemia/small lymphocytic lymphoma.
The incidence was still very small. The study found 9 percent of those who developed one of the cancers had used those high amounts of the acetaminophen, compared to only 5 percent of those who didn't get sick.
The risk is about 1 percent in 10 years of getting one of the cancers for those over age 50, so the increased risk is still only about 2 percent, according to study co-athor Emily White, professor of epidemiology at the Fred Hutchinson Cancer Research Center.
Some experts have called for follow-up studies, USA Today reported this weekend.
The researchers said in that article that "animal studies have linked acetaminophen to toxic effects on bone marrow, which could be why there is a greater risk for blood cancer with long-term use of the drug."
And Reuters reported that earlier research "has linked acetaminophen to asthma and eczema as well, but scientists still don't agree on whether the drug is the actual culprit or just an innocent bystander." It notes the same limitations with this study, since "people who use lots of painkillers could be dealing with medical problems that set them up for cancer down the road."
Email: lois@desnews.com