Introduction Weakened circadian activity rhythm was found to increase dementia and mild cognitive impairment (MCI) among female aged general population, but little is known among pneumoconiosis workers with male predominating.

Objectives This study aims to investigate sleep-wake activity circadian rhythm of patients with pneumoconiosis and test the hypothesis that weakened circadian rhythm is associated with MCI.

Methods We randomly enrolled patients with pneumoconiosis who participated in the annual interview activity. Community controls frequency-matched by age and sex were recruited as the reference. Participants wore wrist actigraphs continuously for 7 days (168 h) after completion of a standardized epidemiological questionnaire. Mesor, doubled amplitude acrophase and percent rhythm are the main circadian parameters and a higher value indicates a more robustness of circadian rhythm. MCI status was assessed using validated Chinese version of Montreal Cognitive Assessment (HK-MoCA) and Mini-mental state examination (MMSE) with a cutoff of 21/22 and 26/27, respectively. Co-variance analysis and multivariate logistic regression were performed to obtain adjusted mean of cognitive score and adjusted odds ratio (AOR).

Results Workers with pneumoconiosis had significantly lower MoCA score than the community controls (20.5±0.4 vs. 22.0±0.5, p=0.03) after age and education were adjusted, while the difference in MMSE score was borderline (25.6±0.3 vs. 26.4±0.4, p=0.08). Mesor and Double amplitude were the circadian parameters that were notably lower among pneumoconiosis workers than the community controls. Compared with community controls with higher Mesor values, pneumoconiosis workers with lower Mesor levels had an AOR of 2.89 (95%CI: 1.20–6.95) for MCI measured by MoCA, which was relatively higher than that of the community controls (AOR=2.73, 95%CI: 0.94–7.93). Similar but attenuated results were observed for double amplitude.

Conclusion This study provides the first epidemiological evidence that increased risks of mild cognitive impairment is associated with weakened circadian rhythm among pneumoconiosis workers.