The agent, host, environment triad is adequate to explain most chronic diseases of non-infectious origin. The existence of a dose-response relationship does not support a view that an association is a causal one. One of the main purposes of descriptive epidemiology is to aid in the creation of hypotheses. The major categories of descriptive epidemiology are person, place, and time. Socioeconomic status is an example of a place variable.
Lung cancer is the leading cause of cancer deaths among both males and females in the United States.
Marriage is hypothesized to act as either a selective or protective factor in health. Numerous epidemiological studies have indicated that race does not influence the incidence and prevalence of disease. Nativity refers to place of origin of an individual. Associations derived from epidemiologic studies are always determined to be causal. Infant mortality rates are higher in the upper social classes than in the lower social classes.