proposed by several authors and institutions ( International Labour Office, 1988; Koller, 1989; Rutenfranz, 1982; Rutenfranz et al., 1985; Scott & LaDou, 1990).
Work at night and on irregular shift schedules should be restricted for people suffering from severe disorders that are associated with or can be aggravated by shift lag and jet lag, in particular, important gastrointestinal diseases (e.g., peptic ulcer, chronic hepatitis, and pancreatitis); insulin-dependent diabetes, as regular and proper food intake and correct therapeutic timing are required; hormonal pathologies (e.g., thyroid and suprarenal gland), because they demand regular drug assumption strictly connected to the activity/rest periods; epilepsy, as the seizures can be favored by sleep deprivation and the efficacy of treatment can be hampered by irregular wake-rest schedules; chronic psychiatric disorders, depression in particular, as they are often associated with a disruption of the sleep /wakefulness cycle and can be influenced by the light/dark periods; chronic sleep disturbances; and coronary heart diseases, severe hypertension, and asthma, as exacerbations are more likely to occur at night and treatment is less effective at certain hours of the day.
Moreover, occupational health doctors should consider very carefully those who may be expected to encounter more difficulty in coping with night work and jet lag on the basis of their psychophysiological characteristics, health, and living conditions, such as age over 50; low amplitude and stability of circadian rhythms; rigidity of sleeping habits and low ability to overcome drowsiness; extreme morningness; high neuroticism; unsatisfactory housing conditions; and women with small children but lacking social support.
Therefore, medical checks have to be focused mainly on sleeping habits and troubles, eating and digestive problems, psychosomatic complaints, drug consumption, housing conditions, transport facilities, work loads, and off-job activities, preferably using standardized questionnaires, checklists, and rating scales, in order to monitor the worker's behavior throughout the years.
Besides this, permanent education and counseling should be provided for improving self-care strategies for coping, in particular as concerns sleep, smoking, diet, drugs, stress management, and physical fitness.
The adoption of these criteria could also improve the efficacy of preemployment screenings, in order to avoid allocating some people, who are more vulnerable in circadian rhythmic structure and psychophysical homeostasis to jobs that require shift and night work.
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