Epidemiology of advanced lung disease in the United States.

ALD affects a large segment of the population in the United States, both old and young, and men and women of all races and ethnicities. Many chronic diseases inevitably advance to a stage that results in significant respiratory impairment and disability. Although the causes of some of the diseases are known and the diseases may be preventable, the overall absolute burden of illness in the population is rising because of an enlarging population and newer therapeutic approaches. This is evident despite the lack of consistent and comparable data estimates for all diseases from national database resources. Where the data exist, it is evident that the cost related to the morbidity and mortality of these illnesses is substantial and consumes a significant proportion of health care expenditures. Both morbidity and mortality estimates, as well as cost estimates, are conservative and are likely underestimates of the true overall impact of ALD on the US economy.