ИСТИНА

Aim: to study the influence of computer’s screen time on indicators of the sensorimotor reactivity, physical development, and cardiovascular system in primary school students. We analyzed the data obtained in Moscow schools in 2006-2011. Surveys were conducted twice a year (October and March-April) in 66 different educational organizations. In total, the study included the data for 4,525 primary students (grades 1-4; 7-12 years). The school and after-school screen time was scored by teachers based on national hygienic standards: 0 points – no load, 1 point - within recommended limits (15 min at school and 30 min out of school), 2 points – 2-fold exceed the recommended limits, 3 points - 3-fold exceed the recommended limits. The sensorimotor reactivity was assessed by reaction time (RT) of simple sensorimotor reactions to light (V) and acoustic (S) stimuli and their ratio RTS/RTV. The following somatic parameters were evaluated: body mass index (BMI), heart rate variability (HRV), blood pressure (BP) and its variability (BPV). A correlation was found between RT (both RTV and RTS) and total (school and after-school) screen time. Excessive screen time (3 points) leads to an increase in RTV during spring testing; this increase was most pronounced in third- and fourth-grade girls. Moreover, seasonal variability of RTS/RTV appears in the form of a decrease in this indicator during spring testing most pronounced in third- and fourth-grade boys. Analysis of indicators of physical development revealed a correlation only between the level of out-of-school screen time and BMI and only in boys: high load (3 points) was associated with BMI increase and changes in its seasonal variability from an increase during winter period to a significant increase during summer period. Analysis of cardiovascular system parameters showed that school screen time of 1 point is associated with an increase in systolic BP within the normal limits in girls by the end of the 2nd and 4th grades and in boys at the beginning and end of the 4th grade. Excessive screen time (2 and 3 points) had no additional effect on BP. However, the pattern of seasonal variability in the total power (TP) of the HRV spectrum in boys under these conditions became opposite to that observed in children who do not use computers at school: TP values became higher during spring testing. These findings attest to pronounced influence of computer loads on the functional state of primary school students. RFBR Project #19-29-14104