Associations of Mentally Active and Passive Sedentary Behavior with Sleep Quality and Duration in Pregnant Women of Advanced Versus Younger Maternal Age

<b>Background/Objectives</b>: To examine associations of mentally active and passive sedentary behavior (SB) with sleep quality and duration in pregnant women of advanced (AMA) and younger (YMA) maternal age, separately, and evaluate effects of SB patterns (weekends vs. weekdays). <b>Methods</b>: This secondary analysis of an observational, clinic-based, cross-sectional study included pregnant women of AMA (<i>n</i> = 225; 37.8 ± 2.6 years) and YMA (<i>n</i> = 710; 27.5 ± 3.8 years) from any trimester. SB and sleep were assessed using the Arabic version of the Sedentary Behavior Questionnaire and the Pittsburgh Sleep Quality Index, respectively. Logistic regression models evaluated associations of maternal mental activity-based SB with sleep outcomes. <b>Results</b>: Higher mentally passive SB on weekdays was unfavorably associated (odds ratios ranged between 1.58 and 2.12; <i>p</i> < 0.05 for all), and on weekends was paradoxically and favorably associated (odds ratios ranged between 0.53 and 0.62; <i>p</i> < 0.05 for all) with sleep quality only in pregnant women of AMA. Higher mentally passive SB across the week or on weekdays was unfavorably associated (odds ratios ranged between 1.11 and 1.65; <i>p</i> < 0.05 for all), while higher mentally passive SB on weekends and mentally active SB across the week or on weekends were paradoxically and favorably associated (odds ratios ranged between 0.57 and 0.91; <i>p</i> < 0.05 for all) with a higher adherence to sleep duration recommendations in both pregnancy groups. <b>Conclusions</b>: These findings suggest that some relationships between mental activity-based SB and prenatal sleep health may vary across maternal age groups. The cross-sectional design limits causal inference, emphasizing the need for longitudinal and randomized studies on mental activity-based SB and sleep health in pregnant women of AMA and YMA.