Trends of Sedentary Time and Domain-Specific Sedentary Behavior in Spanish Schoolchildren.

: To examine the temporal trends of accelerometer-based total daily sedentary time (ST) and self-reported domain-specific sedentary behavior (SB) on weekdays and weekends in Spanish children. : A total of 560 (50.53% girls) children (4th graders) in 2011/12 from 23 Spanish schools and 462 (48.70% girls) children (4th graders) in 2017/18 from 19 schools across Cadiz participated. Hip-worn accelerometers and questionnaires were used to assess total daily ST and self-reported time in SB modalities, respectively. : The objectively measured total daily ST tended to increase in boys on weekdays and weekends. Time spent watching television (TV) decreased during the week and weekend days, while time surfing on the internet increased on weekdays and weekends. Playing video-games increased in boys during the weekends. The trend to increase the time spent on educational activities with a computer during the weekdays and weekends was accompanied by a reduction of the same activities without using a computer. There was a trend to increase reading for fun, talking on the phone and total time in other SB, on weekdays and weekends in boys and girls. : Spanish boys tended to increase objectively measured total daily ST. Moreover, SB modalities have changed in recent years in children, replacing TV viewing by computer use for both educational and non-educational purposes, as well as by the use of smartphones or other sedentary activities that does not imply the presence of a screen. These findings highlight the need to promote interventions to decrease total daily ST and reduce SB activities.