Coughing becomes less effective because of obstructed airflow. Cyanosis People who have a poor supply of oxygen usually have a bluish tinge to their skin, lips, and nailbeds, called cyanosis. It usually begins when patients are in their 60s and 70s and slowly becomes more prominent. It is closely associated with lung function decline and is not always associated with low oxygen in the blood. Patients often wonder why dyspnea occurs so long after beginning to smoke, say 50 to 60 years later.
Some patients have even quit smoking several years before symptoms appear.
The main reason is that lung function declines slowly with age, even in a nonsmoker. Because the lungs have a considerable amount of reserve, a large portion must become nonfunctional before symptoms occur. It can take more than 30 years to lose enough lung function to experience symptoms. When a person quits smoking, the loss in function slows to approximately the rate of a nonsmoker. Quality of life can improve by quitting, even if lung function has already declined.