No link between sleep apnea and cancer

A study shows there is no link between sleep apnea and cancer.

Canadian researchers have found no apparent connection between sleep apnea and cancer in a new study of more than 10,000 people with this common sleep disorder.

People with sleep apnea experience repeated periods of disrupted breathing during sleep. Studies suggesting a link between the condition and cancer risk theorized that low oxygen levels might trigger cell mutations connected with cancer.

"We were not able to confirm previous hypotheses that obstructive sleep apnea is a cause of overall cancer development through intermittent lack of oxygen," said lead author Dr. Tetyana Kendzerska, from the Institute for Clinical Evaluative Sciences and Women's College Hospital at the University of Toronto.

The report, published Aug. 5 in the Canadian Medical Association Journal, is unlikely to put the question to rest, however.

"Additional studies are needed to find out whether there is an independent effect of sleep apnea on specific types of cancer," Kendzerska said.

Dr. Leonard Lichtenfeld, deputy chief medical officer of the American Cancer Society, said the findings suggest that sleep apnea by itself is not related to an increased risk of cancer. "However, for some people the factors that cause sleep apnea are related to an increased risk of cancer," he said.

Risk factors for sleep apnea include smoking, chronic lung disease, obesity and diabetes, Lichtenfeld said. "It is these conditions that are more likely to cause the increased cancer risk seen in other studies, not the sleep apnea itself," he said.

This study isn't the "final answer," he said. "More research will have to be done."

For the study, Kendzerska and colleagues studied about 10,150 patients suffering from sleep apnea who took part in a sleep study between 1994 and 2010. They linked this data to health databases from 1991 to 2013.

At the start of the study, about 5 percent of the patients had cancer. Over an average of nearly eight years of follow-up, an additional 6.5 percent of the participants developed cancer. Most common were prostate, breast, colorectal and lung cancers, the researchers said.

Although no link was seen for cancer in general, the researchers did find that low oxygen levels related to sleep apnea were associated with smoking-related cancers, such as lung cancer.

Dr. Yosef Krespi, director of the Center for Sleep Disorders at Lenox Hill Hospital in New York City, cautioned that while sleep apnea may not cause cancer, it is a serious condition that needs to be treated.

"One should not ignore sleep apnea," Krespi said. "Sleep apnea is a chronic progressive disorder that if left untreated can result in serious heart problems."

More than 18 million American adults have sleep apnea, according to the National Sleep Foundation. Some experts say the condition is increasing because of the obesity epidemic.

Sleep apnea can make a cancer patient's life more difficult, Krespi said.

"The quality of life of sleep apnea patients with cancer and their ability to tolerate treatments such as chemotherapy and radiation can be very different than those without the condition," he said.

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Oxygen Deprivation Before Birth Linked to ADHD Develpoment

Research shows that ADHD may be associated with oxygen deprivation that occurs before birth.

Children who had in-utero exposure to ischemic-hypoxic conditions, situations during which the brain is deprived of oxygen, were significantly more likely to develop attention deficit hyperactivity disorder later in life as compared to unexposed children, according to a Kaiser Permanente study published in the journalPediatrics. The findings suggest that events in pregnancy may contribute to the occurrence of ADHD over and above well-known familial and genetic influences of the disorder.

The population-based study examines the association between IHC and ADHD. Researchers examined the electronic health records of nearly 82,000 children ages 5 years old and found that prenatal exposure to IHC -- especially birth asphyxia, neonatal respiratory distress syndrome, and preeclampsia -- was associated with a 16 percent greater risk of developing ADHD. Specifically, exposure to birth asphyxia was associated with a 26 percent greater risk of developing ADHD, exposure to neonatal respiratory distress syndrome was associated with a 47 percent greater risk, and exposure to preeclampsia (high blood pressure during pregnancy) was associated with a 34 percent greater risk. The study also found that the increased risk of ADHD remained the same across all race and ethnicity groups.

"Previous studies have found that hypoxic injury during fetal development leads to significant structural and functional brain injuries in the offspring," said study lead author Darios Getahun, MD, PhD, of the Kaiser Permanente Southern California Department of Research & Evaluation. "However, this study suggests that the adverse effect of hypoxia and ischemia on prenatal brain development may lead to functional problems, including ADHD."

Researchers also found that the association between IHC and ADHD was strongest in preterm births and that deliveries that were breech, transverse (shoulder-first) or had cord complications were found to be associated with a 13 percent increased risk of ADHD. These associations were found to be the case even after controlling for gestational age and other potential risk factors.

"Our findings could have important clinical implications. They could help physicians identify newborns at-risk that could benefit from surveillance and early diagnosis, when treatment is more effective," said Getahun. "We suggest future research to focus on pre- and post-natal conditions and the associations with adverse outcomes, such as ADHD."

During critical periods of fetal organ development, IHC may result in a lack of oxygen and nutrient transport from the mother's blood to fetal circulation. The result may be compromised oxygen delivery to tissues and cerebrovascular complications. However, this study suggests that the adverse effect of hypoxia on prenatal brain development may lead to functional problems, including ADHD.

In 2005, the Centers for Disease Control and Prevention estimated the annual cost of ADHD-related illness in children under 18 years of age to be between $36 billion and $52.4 billion, making the condition a public health priority. In 2010, approximately 8.4 percent of children ages 3 to 17 had been diagnosed with ADHD. For about half the affected children, the disease persists into adulthood, according to CDC statistics. Symptoms of ADHD in children may include attention problems, acting without thinking, or an overly active temperament.

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