A sample of 73 men and women aged 22-63 years and working in six different occupations (air traffic controllers, waiters, physicians, symphony orchestra musicians, baggagehandlers, and airplane mechanics)participated in a longitudinal study four times during a year. The spontaneous variations in job strain (determined as the self-reported ratio between psychologicaldemands and decision latitude) were substantial. The average difference between the occasion with the highest level of strain and the occasion with the lowest level was 25 Ofo of the total mean. Systolic blood pressureduring workhours, as well as self-reported sleepdisturbance,increased whendemands increased in relation to decision latitude. Among men with a depressive tendency (according to a diary) morning plasma prolactin levels increased markedly with increasing job strain. Among subjects with a positive family history of hypertension the increase in systolic blood pressure at work was particularly pronounced, and among the men in this group a lower than expected levelof morning cortisol was found measured during the period with the highest level of strain.

Mortality is increased in patients with contemporary IIM. The increased mortality was noted within a year of diagnosis, which calls for extra vigilance during the first year of IIM diagnosis.

We present nationwide register-based incidence and prevalence estimates for IIM, robust across three different case definitions. In contrast to many other reports, we did not find incidence by age to be bimodal and we found no explanation of incidence variation across education and residency. These register-based case definitions can be included in future population-based studies to better understand disease aetiology, risk factors and comorbidities.

Infections and respiratory tract diseases are associated with an increased risk of IIM which suggests that the triggering of the immune system may take place outside the skeletal muscle.