A、Men with sleep apnea seldom showed brain problems. B、Women with sleep apnea were more likely to become depressed. C、Most cases

Sleep apnea is a common disorder in which you have one or more pauses in breathing or shallow breaths while you sleep.(12)People with sleep apnea often feel tired and unfocused during the day. But that may not be the only side effect: new research suggests the disorder also dramatically increases the risk of depression.
    Researchers found that men with sleep apnea are more than twice as likely as other men to exhibit signs of clinical depression, such as feeling hopeless and uninterested in everyday activities.(13)The picture was even worse among women: a sleep apnea diagnosis increased the risk of depression symptoms five times.
    What’s more, the study suggests that most cases of sleep apnea are not diagnosed. More than 80% of the people suffering such disorder had never received an official diagnosis. This group, too, had a threefold higher risk of depression compared to people who had no trouble breathing at night.
    Sleep apnea and related problems occur when the airway becomes blocked during sleep, restricting breathing.(14)The disorder can be caused by several factors, including the structure of a person’s airway, or excess fat surrounding the windpipe. Sleep apnea is closely associated with obesity, a fact the researchers took into account by controlling for body mass index in their analysis.
     (15)However, the study shows only an association, not cause and effect, and the researchers can’t rule out the possibility that an unidentified factor could contribute to both sleep apnea and depression.
Questions 12 to 15 are based on the passage you have just heard.
12. According to the speaker, which of the following may be a side effect of sleep apnea?
13. What did researchers find in their study?
14. According to the speaker, which of the following factors can cause sleep apnea?
15. According to the study, what is the relationship between sleep apnea and depression?