A Swedish study found that people who snore are more likely to get cancer. The researchers said that the oxygen deprivation associated with obstructive sleep apnea, or OSA, may be the culprit.

In the United States, about 30 million people suffer from OSA, according to the New York Post, but only 6 million are diagnosed with the condition. Symptoms of the disorder include loud snoring, gasping, and daytime sleepiness.

Dr. Andreas Palm, one of the researchers from Uppsala University in Sweden, said that it is already known that people with OSA are at an increased risk of cancer.

“But it has not been clear whether or not this is due to OSA itself or to related risk factors for cancer, such as obesity, cardiometabolic disease and lifestyle factors,” he said in a press release Monday. “Our findings show that oxygen deprivation due to OSA is independently associated with cancer.”

The researchers also reported data from two other studies that found OSA is linked to a decline in mental processing powers and an increased risk of blood clots. They presented their findings at an international conference in Barcelona, Spain.

 Palm and his colleagues analyzed data from 62,811 patients five years before they started treatment for OSA in Sweden. They linked their data with figures from the Swedish National Cancer Registry and socioeconomic data from Statistics Sweden. They also measured the severity of OSA with the oxygen deprivation index (ODI), which indicates how many times an hour levels of oxygen in the blood fall by at least 3% for ten seconds or longer.

“We found that patients with cancer had slightly more severe OSA,” said Palm. The ODI was higher in patients with lung cancer, prostate cancer, and malignant melanoma.

“The findings in this study highlight the need to consider untreated sleep apnea as a risk factor for cancer and for doctors to be aware of the possibility of cancer when treating patients with OSA. However, extending screening for cancer to all OSA patients is not justified or recommended by our study results,” he added.

Palm said that further research is needed to evaluate more patients and to see if OSA treatment, such as continuous positive airway pressure (CPAP), plays a role in cancer incidence and survival.