INTRODUCTION: Global work patterns are changing, with more individuals engaged in shift work and remaining in the workforce later in life. Shift work is linked to disrupted sleep, impaired cognition, and greater risk of metabolic and neurodegenerative disease; effects that are amplified by aging. However, the neural correlates of shift work remain poorly characterized, leaving a critical gap in understanding how occupational schedules may shape the aging brain.
OBJECTIVES: We aimed to determine the relationship between shift work on brain structure in healthy adults, and how brain structure changes over time in older-aged shift workers.
METHODS: We analysed data from a population-based longitudinal cohort study. We included data for employed individuals with no serious medical conditions. Participants completed self-report questionnaires on health, sleep, cognition and employment, and brain MRI. We used linear regression to compare shift workers and non-shift workers on 153 structural brain parameters, controlling for age, sex, chronotype, intracranial volume, smoking history, MRI head motion, hypertensive status and socioeconomic status.
RESULTS: We included n = 14,198 individuals (aged median 47 [IQR=7] years) comprising non-shift workers (n = 12,076) and shift workers (n = 2122). In shift workers, we detected a symmetrical pattern of volume loss in the right thalamus (Cohen's d=-0.10, adjusted p = 0.026) and left amygdala (Cohen's d=-0.11, adjusted p = 0.010). In subjects who ceased shift work after the baseline, we observed a halting of shift work-related volume loss within 2.4 years. Secondary analyses revealed microstructural degradation in the corticospinal tract, cerebral peduncle and right sagittal stratum, and negative correlation of volume loss with cognitive performance.
CONCLUSION: Shift workers have selective volume loss of the thalamus and amygdala, which is halted within 2.4 years of stopping shift work. Monitoring, counselling and interventional measures, including adjustment of work schedules, could minimise brain volume loss in shift workers.
Circadian Biology