Association of Circadian Rhythm With Mild Cognitive Impairment Among Pneumoconiosis Workers in Hong Kong: a Cross-sectional Study

Background Weakened circadian rhythm was associated with mild cognitive impairment (MCI) in the general population, but it remains unclear among pneumoconiosis patients and this knowledge gap was rectified in this study.Methods This cross-sectional study consisted of 186 male pneumoconiosis patients and 208 age-matched healthy community men who wore a wrist actigraphy for 168 hours and completed a face-to-face questionnaire containing information on sociodemographic, lifestyle behavior, and anthropometric measurements. Circadian activity rhythm was characterized by a cosine model and the parameters included percent rhythm, amplitude, the midline estimating statistic of rhythm (MESOR), and acrophase. Values below the corresponding medians of the circadian rhythm parameters represented weakened circadian rhythm. Cognitive function and MCI or cognitive impairment was assessed by the Cantonese version of Mini-Mental State Examination (CMMSE). Multivariate logistic regression models were used to evaluate the relationships of circadian rhythm with the prevalence of MCI and composite outcome of MCI plus cognitive impairment.Results The mean age of the pneumoconiosis patients was 71.3 ± 7.8 years with the prevalence of MCI and composite outcome of 38.7 % and 50.0 %. Pneumoconiosis patients had worse cognition and dampened circadian rhythm than the community referents. Compared with the community referents or pneumoconiosis patients with robust circadian rhythm, pneumoconiosis patients with weakened circadian rhythm was consistently associated with increased risk of MCI and composite outcome, though the significant association was only for MESOR and the composite outcome with an adjusted OR of 2.01 (95%: 1.03-3.94). A delayed phase of circadian rhythm was insignificantly associated with MCI and composite outcome.Conclusions Weakened circadian activity rhythm among pneumoconiosis workers was positively associated with the prevalence of MCI and composite outcome. Our study suggests that intervention on improving circadian rhythm may mitigate the cognitive deterioration in pneumoconiosis workers.