Sleep apnea may be associated with a small increase in the risk of developing cancer, and that risk may be slightly higher for women with sleep apnea compared to men with the same condition, a new study suggests.
“From the analysis of a large population involving almost 20,000 patients, we concluded that the severity of OSA [obstructive sleep apnea]… was associated with prevalent cancer diagnosis and this association was stronger in females,” Dr. Athanasia Pataka, study lead author and assistant professor of respiratory medicine at Aristotle University in Greece, told Mattress Clarity via email.
Pataka and her team didn’t set out to study a possible link between sleep apnea, sex, and cancer risk. Instead, the purpose of their study, which was published in the European Respiratory Journal, was to explore the association between OSA, intermittent hypoxia (in which the body’s tissues are temporarily deprived of adequate oxygen), and cancer prevalence.
In the process, the team discovered a possible link between sleep apnea and cancer rates as well as higher rates of cancer prevalence in women with OSA. These rates were very small (around 1.7% for men and 2.8% for women).
While much more research needs to be done in order to tease out the correlation between sleep apnea, cancer, and sex, this study provides some insight into these possible links and guides the way toward future research.
Sleep Apnea And Cancer Risk
Obstructive sleep apnea (OSA) is a condition in which a person’s breathing stops and starts during sleep. This reduces blood oxygen levels and tends to provoke sleep disruptions, because people often wake up when their breathing stops temporarily (although people with OSA may not remember these wakeups the next day).
OSA is the most common sleep-related breathing disorder, Pataka told us. An estimated 6.5% to 10% of women have the condition, while between 17% and 31% of men are estimated to have OSA.
Not only do prevalence rates vary by sex, but so may symptoms.
“OSA may manifest differently according to gender,” Pataka says. She says classic OSA symptoms of snoring, sleepiness, and temporary breathing stops are reported more frequently in men, “whereas fatigue, initial insomnia, depression, and morning headaches are more commonly reported in women.”
Previous research has found that if obstructive sleep apnea is left unchecked, it can provoke tiredness, impaired productivity, anxiety, depression, and a higher risk of serious health issues including high blood pressure, irregular heartbeat, heart attack, stroke, and neurological conditions.
In more recent years, research has suggested a possible link between sleep apnea and cancer.
“In the last years, there is evidence that hypoxia and possibly sleep fragmentation — [which] are both aspects of OSA — play an important role in the biology of cancer,” Pataka told us. “In humans, there are studies based on population samples that evaluated if markers of OSA, like the Apnea Hypopnea Index (AHI) or hypoxemia, were associated with an increased risk of cancer.”
Still, the research is far from conclusive.
“Other studies could not confirm the associations between OSA and cancer incidence,” Pataka says. “In a study on a very large population, OSA appeared to increase the risk for selective cancer types [such] as kidney and melanoma, but reduced the incidence of others, like colon, rectal, and lung. The presence of OSA was not associated with increased incidence of metastases or mortality, and in some of the cancer types, a reduced risk of such cancer-related complications was found.”
All told, research into the possible connection between sleep apnea and cancer is still in the early stages.
“The area of research on this topic is still very new and we need more more knowledge about the potential relation between sleep apnea, nocturnal hypoxia, and cancer,” Pataka says. “Especially, the effect of gender on the association between both diseases has not been adequately addressed.”
Analyzing Data from Nearly 20,000 OSA Patients
To further explore the possible link between sleep apnea, hypoxia, and cancer, Pataka and her team analyzed data from the European Sleep Apnoea Database. Adult patients who enrolled in the database between 2007 and 2016 were included in the study, totalling nearly 20,000 multinational participants.
The team found that participants who experienced more airway closures during sleep and whose blood oxygen saturation levels fell below 90% more often were more likely to be diagnosed with cancer than people without OSA.
The researchers also discovered that the prevalence of cancer was higher among women with OSA compared to men with the same condition. Among the study’s participants, 2.8% of women had been diagnosed with a serious cancer compared to 1.7% of men.
Cancer was more common among women than men even after controlling for factors including age, alcohol consumption, body mass index, and smoking. Cancer diagnoses were more likely among women with severe cases of OSA.
While these findings were significant, the rates of cancer diagnosis were still quite low, and the study’s authors encouraged OSA patients not to be alarmed. The study suggests a possible correlation but not causation. What’s more, the researchers were not able to examine all variables related to cancer risk. For instance, the study did not account for factors including physical activity, occupation, and marital status.
Women, Sleep Apnea, And Cancer
While the study in question was not designed to explore the causes of differing levels of cancer risk between sexes, Pataka offers some possible explanations for these unintended findings.
“Potential factors… could include the expression of different cancer subtypes between genders, the different behaviour of specific cancer types under conditions of hypoxia, or the different age of cancer appearance,” she says. “Additionally, the differences on hormonal influences on tumour cell growth and immune responses, the different duration of OSA exposure, as well as gender-specific exposure patterns to cigarette smoking may play a role.”
In a future follow-up study, Pataka and her team are planning to study specific cancer sites and types while exploring cancer incidence and mortality. “Also, it would be interesting to evaluate whether proper treatment of OSA in cancer patients improves survival and cancer outcomes,” Pataka told us.
In the meantime, this study points to the importance of effective OSA diagnosis, especially among women, for whom OSA may manifest differently than men.
“Clinicians should evaluate more carefully female patients for the detection of possible OSA in order to avoid under-diagnosis of the disease,” Pataka told us.
Featured image: sbw18/Shutterstock
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