The smoking and sleep apnea equation. 1 + 1 = 1,000

Are you a smoker? If so, the chances are that you have obstructive sleep apnea. Smokers are three times more likely to have obstructive sleep apnea (OSA) than are people who have never smoked. Nicotine and sleep are a bad combination.
The Correlation
Smoking may irritate the tissues in your nose and throat and cause inflammation and fluid retention in your upper airway. This swelling causes a blockage which restricts air flow.
Both smoking and OSA are deadly conditions that, in combination, will wreak havoc to your quality of life and can severely shorten your life span.
Both sleep apnea and smoking can cause all sorts of cardiovascular and respiratory health problems. OSA can lead to stroke and heart disease while smoking increases one’s chance of contracting mouth, throat and lung cancer. Studies have even shown that sleep apnea victims who smoke, generally have heightened triglyceride levels and lowered HDL levels.
The Studies
The average person loses 1.2 minutes of sleep for every cigarette they smoke, due to nicotine’s stimulating and subsequent withdrawal effects, according to a  2013 University of Florida study,
 

Men’s Health reported, “People who smoke within two hours of bedtime struggle to fall asleep because the nicotine disrupts their natural sleep-wake cycle, and withdrawal symptoms set in before the morning alarm goes off, often leaving smokers feeling even more restless and agitated.”

Patients who suffer from untreated sleep apnea are rarely able to reach the cycles of deep sleep where dreaming occurs. With treatment, patients begin to dream again and it takes time to get used to it.  Vivid dreaming is a common occurrence in those who are in the process of quitting smoking and have begun sleep apnea treatment.
Conclusion
A 2012 report in Chin Med concludes: “Smoking may act as a risk factor for OSA and join with OSA in a common pathway to increase the risk of systematic injury. OSA, in turn, may be a predisposing factor for smoking. Thus, smoking cessation is recommended when considering treatment for OSA, and treating OSA may be a necessary precondition for successful smoking cessation.”
Resources
American Journal of Respiratory and Critical Care Medicine.
Johns Hopkins University 2008 
University of Florida
Chin Med
Mayo Clinic
WebMD