Effects of Selection on Mortality1

A study of twins and stroke.

“…17 Survival for veterans is slightly better compared with the US population of the same sex and age. 18 Additional…”

Occupational mortality studies. Principles of validity.

“…This term usually refers to a tendency for any particular employed population to have lower mortality than the general population. The tendency has been observed for a variety of occupations and causes of death (4,5,8,9,10,14,19,23,24). Thus an observed-to-expected (0 : E) ratio of less than one might still suggest excess mortality as long as the "general population" is used as the reference population.…”

“…The reason is that the magnitude of the healthy worker effect is not constant but varies according to many factors, ie, (i) cause of death (4,5,8,9,10,14,16,19,23,24), (ii) demographic factors [It varies by occupation and work category (4,5,8,9,10,14,16,19,23,24,27), is usually -stronger for nonwhites than whites (4,5,14,16) and stronger for the young than for the old (9,16), generally decreases with early retirement (6, 28), etc. ], and (iii) time lag since starting the work or -since the zero time of a cohort [It is prominent at the beginning and tends to decline with the passage of time (6,9,16,20,24,28).] Quantification of the healthy worker effect specific for such factors also does not seem to provide a general solution to the problem.…”

“…As many authors have pointed out, the healthy worker effect arises from the use of the general population as the reference population (6,8,9,10,11,14,16,19,20,23,24,27). Each occupational setting has its characteristic requirements and incentives for job entry (2,6,8,9,10,14,16,19,20,24) and exit (2,6,9,10,14,16,20), and these, when different for the index occupation and the "general population" and also when related to mortality, produce the healthy worker effect.…”

“…Each occupational setting has its characteristic requirements and incentives for job entry (2,6,8,9,10,14,16,19,20,24) and exit (2,6,9,10,14,16,20), and these, when different for the index occupation and the "general population" and also when related to mortality, produce the healthy worker effect. By the same token, if the use of the general population is replaced by the use of an occupational population with comparable job entry and exit factors, then there is no healthy worker effect.…”