Shift or night shift work and dementia risk: A systematic review

OBJECTIVE: Dementia is a neurodegenerative disorder characterized by a progressive decline in multiple cognitive domains. Individual and/or environmental risk factors, i.e., aging, are involved in its pathogenesis. It is possible that shift and night works, affecting circadian rhythms, may contribute to the occurrence/progression of the disease. Therefore, aim of this review was to provide an overview on the possible association between shift or night work and cognitive decline. MATERIALS AND METHODS: A systematic review of literature studies available in PubMed, Scopus, and ISI Web of Science databases, addressing the possible relationship between shift or night work and dementia was performed. RESULTS: Not-homogeneous findings emerged from the revised studies. Some results supported a positive association between shift work and increased risk of dementia, although with a not unique evidence concerning the role of night work schedules and the consequent circadian misalignment in disease pathogenesis. Cardiometabolic disorders, underlying lifestyles, and additional occupational risk factors, including, psychosocial stress, may act as mediators in the shift work-dementia relationship, that may be overall affected by the individual genetic susceptibility too. Length of employment in shift works was also suggested to be responsible for cognitive damaging effects. CONCLUSIONS: The limited number of available studies, the several and different work schedules analyzed, together with the possible co-exposure to other occupational risk factors prevent to draw conclusions on shift work-dementia relationship. Further research should confirm such association and the causal relation with early cognitive alterations in order to guide suitable occupational risk assessment, as well as to promote healthy lifestyle and occupational management strategies, with the ultimate goal of preventing cognitive decline of shift workers. This may overall support the active aging of the workforce while providing benefits for the public health system.