The prognosis in patients with mild airway obstruction is good, but for those with severe obstruction the prognosis is poor, particularly if the blood level of carbon dioxide is high. In most cases, death from COPD is precipitated by acute respiratory disease such as pneumonia or by other complications such as cardiac arrhythmia or pulmonary embolism. About two million Americans have emphysema, and another 14 million have some form of chronic bronchitis. About 105,000 died of COPD in 1996, making it the fourth leading cause of death in the U.S. after coronary heart disease, stroke and lung cancer. Nineteen out of 20 of those dying of COPD are 55 or older.
Men are more likely to die of the disease than women.
The reasons for the regional differences in mortality are not clear, but it may be no accident that deaths from COPD and lung cancer are greater in the Southeast, where smoking is historically high. COPD mortality, unlike that of lung cancer, tends to increase with altitude, as illustrated by the high mortality rates in the mountain states. Altitude as a disease contributor has not been established but is biologically plausible. Those living in Denver, for example, get 15 percent less oxygen in the same volume of air as those living in a sea-level city such as Miami and so, if they have developed COPD, could be at higher risk of death.