Shift work disrupts body rhythms, accelerates cognitive decline later in life

What is it about?

Shift work may have lasting effects on cognitive health, according to researchers at Texas A&M University College of Medicine, who have published a study exploring possible links between dysregulation of circadian or 24-hour body rhythms and cognitive impairment during aging in the Journal of Neuroinflammation. Conducted by David Earnest, PhD, Karienn de Souza, PhD, and M. Karen Newell-Rogers, PhD, the study produced groundbreaking results, indicating that circadian rhythm alterations in response to shift work-like schedules during early adulthood persisted into middle age. According to Earnest, past clinical literature suggests that people with abnormal work or social schedules are more susceptible to an array of health disorders, including cardiovascular disease, diabetes and cancer. With De Souza’s expertise in cognition and aging and Earnest’s in how internal body clocks control circadian rhythms and sleep, Earnest said discussions naturally veered toward expanding upon previous research to explore the potential link between shift work and health later in life, specifically related to memory and cognitive decline. Earnest said he and de Souza used an animal model to focus this research on the time of life equivalent of young adults aged 18–26—when people are most likely to engage in shift work based on human demographics. “We were interested in following up on our previous observations examining associations between age-related changes in cognition and circadian rhythms to determine whether or not circadian rhythm dysregulation by itself is a long-term risk factor for accelerated cognitive decline later in life,” Earnest said. Results indicate circadian rhythm dysregulation dramatically accelerates cognitive decline at middle age—much earlier than learning and memory deficits usually occur—and is linked with long-term alterations in the regulation of immune cells and cells in the brain called microglia that contribute to inflammatory processes associated with neurodegenerative diseases. In turn, these findings suggest shift-work-related dysregulation of circadian rhythms, independent of aging and other variables associated with dementia, is a long-term risk factor for activation of neuroinflammatory immune cells and accelerated decline in learning and memory during aging.

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Why is it important?

Study demonstrates for the first time that: 1) early circadian rhythm dysregulation alone, independent of aging and other risk factors for dementia, accelerates cognitive aging such that severe deficits occur at middle age; and 2) Stable regulation of circadian rhythms is a key factor in the resilience to age-related cognitive decline