There is a review article in the Journal of Clinical Sleep Medicine about a relationship between chronic cough and obstructive sleep apnea (OSA). Chronic cough is a significant problem, and in non-smokers, is usually due to post-nasal drip (now called upper airway cough syndrome), gastroesophogeal reflux disease (GERD), or cough-variant asthma.
The authors discussed a couple of cases where patients with chronic cough were diagnosed with OSA, treated with CPAP, and their chronic cough improved dramatically. The authors speculate that OSA could be associated with chronic cough by being related to the reasons patients get post-nasal drip, GERD, or cough-variant asthma. GERD and OSA have already been associated by prior studies. OSA can result in inflammation of the upper airway, which could contribute to post-nasal drip. Finally, studies are showing a relationship with asthma and OSA. Also, OSA by itself has been associated with airway inflammation, be it from repetitive oxygen drops, direct trauma from vibrating tissue, or from the bloodstream. This inflammation could result in chronic cough. So if you have a chronic cough, talk to your doctor about being evaluated for obstructive sleep apnea.