The Woolcock Institute of Medical Research

A new international study published in the Journal of Sleep Research has found that treating obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) does not appear to significantly reduce the risk of developing cancer.

OSA has long been suspected to contribute to cancer development, largely due to repeated drops in oxygen levels during sleep. CPAP – the standard treatment for moderate to severe OSA – keeps airways open overnight, prompting interest in whether controlling the condition could also lower cancer risk.

To explore this, researchers conducted a meta-analysis of three major randomised controlled trials which included patients with moderate to severe OSA who were randomly assigned to receive CPAP therapy or no CPAP.

Across all three studies, cancer rates were similar between those using CPAP and those who were not. When the data were combined, the analysis showed no statistically significant difference in cancer incidence between the two groups.

While the findings suggest that CPAP does not markedly influence cancer risk, the researchers caution that the results are not definitive. The confidence interval was wide, meaning the analysis cannot rule out the possibility that untreated OSA may either increase or decrease cancer risk.

The trials followed participants for approximately three to four years and primarily involved middle-aged to older men with existing cardiovascular disease – factors that may limit the ability to detect longer-term cancer outcomes.

Previous observational studies examining links between OSA and cancer have produced mixed results, but are more vulnerable to bias. By focusing on randomised trials, this analysis provides a more robust assessment of whether treating sleep apnoea changes cancer risk.

But, the analysis also highlights important limitations in the current available evidence. While randomised controlled trials reduce many of the biases seen in observational research, the authors note that the available trials were not designed to assess cancer outcomes.

Woolcock Sleep and Circadian Research group clinical triallist and epidemiologist Professor Nathaniel Marshall, a co-author on the study, contributed to the analysis, which found that the trials were relatively small, of limited duration, and focused on patients with high cardiovascular risk rather than cancer risk.

As a result, the studies may be underpowered to detect any true effect of CPAP on cancer incidence, and the wide confidence intervals mean the findings cannot rule out either increased or decreased risk.

Importantly, the findings do not alter the well-established benefits of CPAP for improving sleep quality, reducing daytime sleepiness, and supporting cardiovascular health in people with OSA.

In the absence of large, long-term trials specifically designed to assess cancer outcomes, researchers say uncertainty around the relationship between sleep apnea, its treatment, and cancer risk is likely to remain.

Find out more

• Journal of Sleep Research - CPAP to Reduce the Risk of Cancer in OSA?
• Sleep and Circadian Research at the Woolcock
• Professor Nathaniel Marshall