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Eng King Tan

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2 papers

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YNIMG Journal 2025 Journal Article

Shift work is associated with selective brain volume loss: a longitudinal study

Thomas Welton
Thomas Wei Jun Teo
Seyed Ehsan Saffari
Ling-Ling Chan
Eng King Tan

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.

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YNICL Journal 2021 Journal Article

Utility of quantitative susceptibility mapping and diffusion kurtosis imaging in the diagnosis of early Parkinson’s disease

Samantha Tan
Septian Hartono
Thomas Welton
Chu Ning Ann
Soo Lee Lim
Tong San Koh
Huihua Li
Fiona Setiawan

OBJECTIVE: To investigate the utility of quantitative susceptibility mapping (QSM) and diffusion kurtosis imaging (DKI) as complementary tools in characterizing pathological changes in the deep grey nuclei in early Parkinson's disease (PD) and their clinical correlates to aid in diagnosis of PD. METHOD: Patients with a diagnosis of PD made within a year and age-matched healthy controls were recruited. All participants underwent clinical evaluation using the Unified Parkinson's Disease Rating Scale (MDS-UPDRS III) and Hoehn & Yahr stage (H&Y), and brain 3 T MRI including QSM and DKI. Regions-of-interest (ROIs) in the caudate nucleus, putamen, globus pallidus, and medial and lateral substantia nigra (SN) were manually drawn to compare the mean susceptibility (representing iron deposition) and DKI indices (representing restricted water diffusion) between PD patients and healthy controls and in correlation with MDS-UPDRS III and H&Y, focusing on susceptibility value, mean diffusivity (MD) and mean kurtosis (MK). RESULTS: There were forty-seven PD patients (aged 68.7 years, 51% male, disease duration 0.78 years) and 16 healthy controls (aged 67.4 years, 63% male). Susceptibility value was increased in PD in all ROIs except the caudate, and was significantly different after multiple comparison correction in the putamen (PD: 64.75 ppb, HC: 44.61 ppb, p = 0.004). MD was significantly higher in PD in the lateral SN, putamen and caudate, the regions with the lowest susceptibility value. In PD patients, we found significant association between the MDS-UPDRS III score and susceptibility value in the putamen after correcting for age and sex (β = 0.21, p = 0.003). A composite DKI-QSM diagnostic marker based on these findings successfully differentiated the groups (p < 0.0001) and had "good" classification performance (AUC = 0.88). CONCLUSIONS: QSM and DKI are complementary tools allowing a better understanding of the complex contribution of iron deposition and microstructural changes in the pathophysiology of PD.

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