Sleep deprivation as a risk factor for cortical gray matter reduction in new medical residents

Sleep is an essential physiological condition for the proper functioning of humans, both physiologically, cognitively, and psychologically. Sleep deprivation leads to a loss of psychomotor skills in humans. It is important to evaluate the structural changes experienced by medical residents who are sleep-deprived due to extensive work shifts, including night shifts, assigned during their training program. Therefore, the main outcome was to evaluate the structural changes in the cortical gray matter and the hippocampus assessed by brain magnetic resonance imaging (MRI) in newly admitted medical residents four months after the start of the medical specialty.

Forty-one newly admitted medical residents were enrolled, and an initial questionnaire was administered to assess sleep quality. All participants underwent a brain MRI study, utilizing an advanced MRI sequence: a 3D inversion recovery (IR)-prepped fast spoiled gradient-recalled (SPGR) high-resolution T1-weighted sequence. The images were then anonymized and reformatted, and volumetric analyses of gray matter and hippocampus were performed using an open-access platform for MRI brain analysis (volBrain). This process was repeated four months later with the acquisition of a new brain MRI study for each participant.

For gray matter volume, a baseline value of 728.04 ± 63.95 cm³ and a final value of 715.11 ± 59.38 cm³ were found (p < 0.01), and the frontal lobe showed the greatest reduction, with an initial value of 181.92 ± 15.58 cm³ and a final volume of 176.45 ± 17.35 cm³ (p = <0.001). We found an OR of 1.52 (95 % CI 0.93-4.14, p = 0.01) between working night shifts and gray matter reduction.

The results of this study show a statistically significant reduction in gray matter volume in first-year residents after four months of shift work, with the greatest reduction in the frontal lobe.