Health selection among members of a Danish Trade Union

The effect of selection on the mortality of members of the Danish carpenters and cabinet makers trade union is reported. Some 40 000 persons entering or leaving the Union between January 1971 to June 1976 were followed until September 1977, and deaths identified by record linkage with the central person-register. The male leaving cohort had a statistically significant higher age adjusted mortality rate than the male entry cohort with a relative death risk of 1.65. For females the difference was not significant but the relative death risk was estimated to be 1.42. Males leaving to or coming from well paid and socially esteemed jobs had significant lower mortality rates than the remainder. The influence of these results on the choice of study design is discussed.