The authors analyzed as a function of age the relationships between certain health problems and shiftwork, on the basis of a French epidemiologic study of health, work, and aging that included 21,378 subjects. Sleep disorders, Nottingham Health Profile data (energy, social isolation, emotional disorders), and health indicators such as the number of sick leaves, the condition of being overweight, and the use of neuropsychiatric drugs were affected by age and shiftwork (with additive effects for the two factors). The authors found no correspondence between work schedules and hypertension. The different types of shiftwork did not produce the same results: regular night work was better tolerated than night work included in a system of rotating shifts. Finally, there was a cumulative effect for age and shiftwork, with an increasing risk of crossing a threshold beyond which a schedule is no longer tolerated.