A behavioral or environmental factor that has a remote or indirect causal influence on a specific disease outcome. Many etiological factors in chronic diseases fall into this category. This does not mean a relationship that is remote in time, or one that has a long latency period, but one that acts indirectly by way of its influence on the chain of causation. An example is the presence in the atmosphere of ozone-destroying substances, such as freon gas from air conditioning equipment leading to attenuation of the ozone layer, higher levels of biologically active ultraviolet solar radiation, and consequently greater risk of skin cancer and cataract. Thus, the use of ozone-destroying substances is a distal risk factor for skin cancer and cataract.
Subjects: Public Health and Epidemiology.