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24-05-2012 | Psychology | Article

Sleep apnea linked to cancer death risk


Free abstract

MedWire News: Sleep-disordered breathing (SDB), or sleep apnea, is associated with an increased risk for cancer mortality, study findings show.

"Remarkably, the association was stronger in relative terms than that of SDB with mortality from all causes as well as that previously observed for cardiovascular mortality," say F Javier Nieto, from the University of Wisconsin School of Medicine and Public Health in Madison, USA, and colleagues.

Data on 1522 participants of the Wisconsin Sleep Cohort were studied. Of these, 222 had mild SDB (apnea-hypopnea index [AHI]=5 to 14.9 apnea and hypopnea events per hour of sleep), 84 had moderate SDB (AHI=15 to 29.9), and 59 had severe SDB (AHI=30 or above or had a continuous positive airway pressure [CPAP] device present during sleep assessment).

Over a 22-year period, there were a total of 112 deaths, of which 50 were attributed to cancer, the most frequent being lung cancer (n=8).

After adjusting for age, gender, body mass index, and smoking, SDB showed a dose‑response relationship with cancer mortality.

Patients with mild SDB were 1.1 times more likely to die from cancer than individuals without SDB, while those with moderate and severe SDB were a respective 2.0 and 4.8 times more likely. This relationship persisted when patients treated with CPAP were excluded from analyses.

The researchers note that the risk for cancer mortality also increased in line with hypoxemia index severity. Participants in the top hypoxemia index category (11.2% of the night at less than 90% oxygen saturation) had a more than eight times higher risk for cancer mortality than those in the lower category (0.8% of the night at less than 90% oxygen saturation).

This finding supports previous animal studies showing an association between intermittent hypoxia and accelerated cancer progression, and therefore hints at a mediatory effect of hypoxia on increased tumor tissue angiogenesis and resulting cell proliferation and tumor growth, the researchers explain.

They conclude in the American Journal of Respiratory and Critical Care Medicine that if their findings are validated in further clinical and population-based studies, "diagnosis and treatment of SDB in cancer patients may be indicated to prolong survival in cancer patients."

By Lucy Piper

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