Physical Activity, Screen Time, Cardiorespiratory Fitness, and Selective Attention in Primary School Children: A Cross-Sectional Study

Background: Physical activity, screen time, and cardiorespiratory fitness have been associated with cognitive functioning in children; however, their mutually adjusted associations with specific dimensions of selective attention remain insufficiently understood. This study examined the associations of habitual physical activity, screen time, and cardiorespiratory fitness with selective attention in primary school children. Methods: This cross-sectional study included 386 children aged 9–12 years (54.4% girls). Habitual physical activity was assessed using the Physical Activity Questionnaire for Children (PAQ-C), screen time using the Youth Leisure-Time Sedentary Behavior Questionnaire (YLSBQ), cardiorespiratory fitness using the 20 m shuttle run test, and selective attention using the d2-R Test of Attention. Selective attention was characterized by processing speed (TR), percentage of errors (E%), and concentration performance (CON). Associations were examined using correlation and multiple linear regression analyses adjusted for age and sex, followed by hierarchical regression models examining the mutually adjusted associations of physical activity, screen time, and cardiorespiratory fitness with selective-attention outcomes. Results: Higher physical activity was significantly associated with a greater number of total items processed (TR; B = 69.87, β = 0.660, p < 0.001), a lower percentage of errors (E%; B = −1.75, β = −0.356, p < 0.001), and better concentration performance (CON; B = 26.44, β = 0.659, p < 0.001). Greater screen time was primarily associated with a higher error percentage (β = 0.597, p < 0.001), while associations with processing speed and concentration performance were weaker. Higher cardiorespiratory fitness was associated with greater processing speed (β = 0.468), fewer errors (β = −0.455), and better concentration performance (β = 0.667; all p < 0.001). In the final hierarchical models, after mutual adjustment for physical activity, screen time, cardiorespiratory fitness, age, and sex, physical activity was associated with processing speed (β = 0.600, p < 0.001), whereas screen time and cardiorespiratory fitness were not associated with this outcome. For attentional errors, higher screen time (β = 0.523, p < 0.001), lower physical activity (β = −0.117, p = 0.014), and lower cardiorespiratory fitness (β = −0.270, p < 0.001) were associated with a higher error percentage. For concentration performance, both physical activity (β = 0.395, p < 0.001) and cardiorespiratory fitness (β = 0.412, p < 0.001) were positively associated, whereas screen time was not associated with this outcome. Conclusions: Physical activity, screen time, and cardiorespiratory fitness showed distinct associations with specific components of selective attention. Higher physical activity was particularly associated with faster processing speed, higher screen time with greater attentional errors, and both physical activity and cardiorespiratory fitness with better concentration. Given the cross-sectional design, these findings should be interpreted as associations rather than causal relationships.