Sleep disordered breathing is relatively common in the U.S., affecting an estimated 26% of adults. Among all sleep disorders, obstructive sleep apnea (OSA) is one of the leading types. OSA not only negatively impacts sleep quality and leads to daytime drowsiness, but it is also associated with an increased risk for hypertension, cardiovascular disease, and type 2 diabetes. More recent studies have also linked OSA to an increased risk of death due to cancer, and subsequent research investigated whether OSA is also associated with the incidence of cancer. However, results have been mixed, with some studies reporting OSA patients have an increased risk of cancer risk while other studies did not find an association. Researchers from Dr. Amanda Phipps’ research group in the Division of Public Health Sciences recently published results from a new study in the journal Preventive Medicine Reports that probed whether the severity of OSA is associated with risk for several different types of cancer.
Arthur Sillah, graduate student in the Cancer Epidemiology Program and lead author of the new study, described previous Fred Hutch research (Sillah et al., 2018) that motivated the investigation, “This study was built off our previous work, in which we evaluated the association of sleep apnea with several specific cancer types via linkage between administrative databases at UW Medicine and our Cancer Surveillance System (CSS) population-based cancer registry. The results of that study suggest that sleep apnea is a risk factor for cancer, and that this association likely differs across types of cancers including kidney cancer and melanoma.” In the new study, the authors took the work a step further, “There is growing evidence linking obstructive sleep apnea (OSA) and cancer risk, and we expanded on this evidence to look at whether OSA severity was important to cancer,” said Sillah.
The authors conducted a case-cohort study to address their question and utilized records from the University of Washington Medicine system to identify patients diagnosed with OSA over a ten-year period. They then linked the identified cohort with the CSS of Western Washington State to identify subsequent cancer diagnoses. From the parent cohort of more than 15,000 patients, they selected a random sub-cohort of 1,162 individuals who did not have cancer at the time of the initial OSA diagnosis. Twenty-four of these patients later developed cancer. To increase the number of cases in the study, the authors then included all other patients in the parent cohort who developed cancer after their OSA diagnosis, 304 individuals. Taken together, the study included 1,466 OSA patients, of which 328 developed cancer subsequent to OSA.
Severity of OSA was determined from review of medical records that included reports from polysomnography (PSG) tests or sleep studies. Five measures were used to classify patients as having mild, moderate, or severe OSA. Within each of the five OSA measures, there were no significant associations between overall risk for cancer and OSA severity. Next, the authors assessed the proportion of participants that had severe OSA (categorized by the five OSA measures) across nine different types of cancer (breast, colorectal, corpus uteri, kidney, lung, lymphoma, melanoma, prostate, and thyroid; see Figure). Compared to the total sub-cohort that included all OSA severity levels, patients with melanoma or cancer of the prostate, corpus uteri, or lung were more likely to have severe OSA in all five severity measures. In addition, the proportion of patients with severe OSA was higher for kidney cancer patients for four out of five of the severity measures. Sillah summarized the findings, “While our results did not find an association with cancer overall, we did find that, among people with OSA, the prevalence of severe OSA was higher than expected for patients with several different cancer types.”
The results from this study will drive follow-up work to further clarify the potential relationship between OSA and cancer. “The fact that we couldn’t find any associations with obstructive sleep apnea severity and overall cancer risk suggest that the underlying process by which this occurs, particularly with respect specific types of cancer, warrants further study. In particular, studies using large population or clinical-based samples to examine specific cancer types in relation to obstructive sleep apnea are needed,” said Sillah. Indeed, if any level of OSA is associated with cancer risk, teasing out the associations by severity level would require much larger sample sizes, as the authors noted in the paper.
This work was supported by the National Institutes of Health.
Fred Hutch/UW Cancer Consortium member Dr. Amanda Phipps contributed to this research.
Sillah A, Watson NF, Gozal D, Phipps AI. 2019. Obstructive sleep apnea severity and subsequent risk for cancer incidence. Preventive Medicine Reports.doi:10.1016/j.pmedr.2019.100886.
Sillah A, Watson NF, Schwartz SM, Gozal D, Phipps AI. 2018. Sleep apnea and subsequent cancer incidence. Cancer Causes & Control, 29(10), 987-994.