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Two recent studies from Pitt Psychiatry have examined neurocognitive and cardiometabolic function in retired night shift workers compared with retired day shift workers. The late Tica Hall, PhD, an internationally recognized expert in sleep and circadian science, served as senior author of both studies, and we recognize this important work in honor of her memory.

Cardiometabolic function in retired night shift workers and retired day workers

Nearly 20% of the world’s labor force routinely engages in work at night during typical sleeping hours (i.e., between midnight and 6:00 a.m.). The biological disturbances resulting from disrupted circadian sleep-wake rhythm may explain findings of increased risk for adverse cardiometabolic health outcomes among night shift workers. Adverse effects of night shift work on metabolic function my also differ by sex. 

In an observational study published in Scientific Reports, Dr. Hall and investigators including Brian Chin, PhD (postdoctoral scholar); Matthew Lehrer, PhD (Assistant Professor of Psychiatry); Eunjin Tracy, PhD (postdoctoral scholar); Kristine Wilckens, PhD (Assistant Professor of Psychiatry); and Daniel Buysse, MD (Distinguished Professor of Psychiatry, Medicine, and Clinical and Translational Science, and UPMC Endowed Chair in Sleep Medicine), evaluated whether retired night shift workers and retired day workers differed in their cardiometabolic function. The investigators found mixed evidence that past night shift work exposure was associated with poorer cardiometabolic function. Retired night shift workers had 2.6-times higher odds of metabolic syndrome prevalence than retired day workers. They additionally found that women retired night shift workers had higher prevalence of high body mass index than women retired day workers, and that men retired night shift workers had higher prevalence of high triglycerides than men retired day workers.

“Night shift work is both necessary for society and risky for individual health,” said Dr. Buysse, the study’s corresponding author. “We found that the risks of night shift work don’t completely resolve with retirement. Current and former shift workers should be monitored closely for cardiovascular and metabolic health problems.”

Chin BN, Lehrer HM, Tracy EL, Barinas-Mitchell E, Wilckens KA, Carroll LW, Buysse DJ, Hall MH. Cardiometabolic function in retired night shift workers and retired day workers. Scientific Reports 13, 5204 (2023). https://doi.org/10.1038/s41598-022-20743-1 

Retired night shift workers exhibit poorer neurocognitive function compared to retired day workers

Shift work is associated with compromised cognitive function, with potential to place workers with chronic exposure at elevated risk for dementia. However, evidence of cognitive impairment among former night shift workers is mixed, possibly due to inconsistencies regarding retirement status, work history classification, and cognitive assessments. To address these limitations, Dr. Hall and Pitt Psychiatry scientists including Matthew Lehrer, PhD (Assistant Professor of Psychiatry); Meryl Butters, PhD (Professor of Psychiatry and Clinical and Translational Science); and Daniel Buysse, MD (Distinguished Professor of Psychiatry, Clinical and Translational Science, and Medicine and UPMC Endowed Chair in Sleep Medicine), compared neurocognitive function between retired night shift workers and retired day workers to determine whether long-term exposure to night shift work is related to cognitive function in retirement. The investigators found that retired night shift workers exhibited poorer executive function and attention compared with retired day workers. 

“Retired night shift workers displayed subtle cognitive weaknesses consistent with elevated risk for dementia,” said Dr. Lehrer, the study’s co-first author. “These results were not explained by poorer sleep in retirement, so other factors—potentially experienced during shift work—should be considered. Retired shift workers should be followed over time to determine whether observed cognitive weaknesses become more pronounced with aging.”

Runk A, Lehrer HM, Butters MA, Buysse DJ, Evans MA, Krafty RT, Hall MH. Retired night shift workers exhibit poorer neurocognitive function compared to retired day workers, Sleep, 2023, zsad098, https://doi.org/10.1093/sleep/zsad098