| Objective:To understand the variations of serum vitamin A level,percentages of,vitamin A deficiency and marginal vitamin A deficiency in students who were in the National Nutrition Improvement Programme for Rural Compulsory Education Students(NIPRCES)during 2014 to 2016.The risk factors affecting serum vitamin A,vitamin A deficiency and marginal vitamin A were explored at different levels(individual-level.school-level and county-level).The purpose of the study is to provide scientific data and policy recommendations for improving the nutritional intervention measures.Methods:The multi-stage stratified random cluster sampling method was applied to select the primary students and primary middle school students of the 50 key monitoring counties in the NIPRCES implementation area.Blood were collected on-site and serum retinol levels were analyzed through laboratory testing.The information of students,schools and counties were collected by unified questionnaires.The vitamin A levels of students surveyed at least twice during 2014 to 2016 and other factors were selected and analy’zed by SAS 9.4 software.The distribution of serum retinol level,percentages of vitamin A deficiency and marginal vitamin A deficiency were described at time,population,and region-level.The multi-level model was used to analyze the risk factors associated with serum retinol level of students,the generalized estimation equation and the fixed-effect logistic regression model were applied to analyze the risk factors associated with percentages ofvitamin A deficiency and marginal vitamin A deficiency of students.Results:In total,6,693 students were included in the study.In 2014.a total of 4001 students were included in the cohort,among which the proportion of male students were 50.6%(in 2014),51.3%(in 2015)and 49.4%(in 2016),respectively,and the proportion of female students were 49.4%(in 2014),48.7%(in 2015)and 50.6%(in 2016).respectively,the proportion of primary middle school students were 28.2%(in 2014),30.0%(in 2015)and 23.8%(in 2016),respectively,and the proportion of primary school students were 71.8%(in 2014),70.0%(in 2015)and 76.2%(in 2016),respectively.In 2015.there were another 2692 students joined the cohort,in which the proportion of male students were 51.8%(in 2015)and 51.8%(in 2016),respectively,and the proportion of female students were 48.2%(in 2015)and 48.2%(in 2016).respectively,the proportion of primary middle school students were 38.9%(in 2015)and 39.6%(in 2016),respectively,and the proportion of primary school students were 61.1%(in 2015)and 60.4%(in 2016).respectively.The mean values of serum retinol in the students who entered the cohort in 2014 were 0.32 μg/mL(in 2014),0.34)μg/mL(in 2015),and 0.36 μg/mL(in 2016),respectively,and increased over time(estimated value=O.0215,t=21.11.P<0.0001).The mean serum retinol level of girls was higher than that of boys(the main effect of gender:estimated value=0.0053,t=2.05,P=0.0409).The serum retinol level of students increased with age.The mean serum retinol level ofthe students who entered the cohort in 2015 were 0.32μg/mL(in 2015)and 0.35μg/mL(in 2016),respectively,and increased over time(estimated value=0.0218,t=12.59.P<0.0001).The mean serum retinol level in girls was higher than that in boys(main effect of gender:estimated value=0.0163.t=5,52,P<0.0001).The serum retinol level of students increased with age.The vitamin A deficie,ncy rates ofthe students who entered the cohort in 2014 were 8.7%(in 2014),2.4%(in 2015)and 0.7%(in 2016),respectively,and decreased over time(estimated value of time effect =-1.3220.z=-14.44.P<0.OOO1)at a decreasing rate of 92.0%.There was no statistically significant difference in vitamin A deficiency rate between male and female students.With the increase of age,the vitamin A deficiency rate of students decreased.The percentage of vitamin A deficiency among students in western China was higher than that in central China(the estimated value of main effect between regions=0.5311,=4.41,P<0.0001).The vitamin A deficiency rate of the students who entered the cohort in 2015 were 3.1%(in 2015)and 1.4%(in 2016),respectively,and declined over time(estimated value of time effect =-0.8107,z=-4.54.P<0.0001)with a decreasing rate of 54.8%.There was no statistically significant difference in vitamin A deficiencv rate between male and fe,male students.The rate of vitamin A deficiency decreased with age.The marginal vitamin A deficiency rate of the students x~who entered the cohort in 2014 were 42.3%(in 2014),29.0%(in 2015)and 14.2%(in 2016),respectively,and decreased year by year(estimated value oftime effect =-0.7229,z=-26.32,P<0.0001)with a decreasing rate of 66.4%The marginal vitamin A deficiency rate of female students declined significantly more than that of male students.With the increase ofage.the rate of marginal vitamin A deficiency of students showed decreased.The rate of marginal vitamin A deficiency of students in western China was higher than that in central China(the main effect estimation value of inter-regional differences=0.1848,z=2.93.P=0.0034),and the rate ofmarginal vitamin A deficiency of students in western China decreased more over time(the interactive effect estimation value of regional differences and time=-0.1894,z=-3.43.P=0.0006).The marginal vitaImin A deficiency rate of the students who entered the cohort in 2015 were 35.4%(in 2015)and 18.6%(in 2016),respectively,and decreased over time(estiimated value oftime effect=-0.8765,z=-15.97.P<0.0001).The rate ofmarginal vitamin A deficiency in girls decreased more rapidly than that in boys.With age increased,the rate of marginal vitamin A deficiency of students decreased.The marginal deficiency rate of students in the western China was higher than that in the central China(the estimated value of main effect between regions=0.3317,z=1.98.P=0.0472).The influencing factors associated with vitamin A status of students included gender,age,meat intake frequency and the school food supply pattern.For the students who entered the cohort in 2014.the serum retinol level was higher but rates of vitamin A deficiency and marginal vitamin A deficiency were the lower in students with frequent intake of meat(eating meat 5 times or more per week).The students’vitamin A status was higher with canteen meal supply mode.The per capita income of different counties had a positive effect on the serum retinol levels of students but not on the vitamin A deficiency or marginal deficiency status of the population.Conc usion:The students’vitamin A status were improved with the implementation of NIPRCES,and the vitamin A deficiency rate declined year by year in 2014 to 2016.The long-term implementation of NIPRCES should be encouraged to produce a persistent improvement.Factors positively associated with vitamin A status in students included frequent intake of meat and the mode ofcanteen food provision.Higher annual income per capita of rural residents was positively associated with the serum retinol levels of students,but did not play a role in improving the vitamin A status.Improving the marginal vitamin A deficiency should be the focus of vitamin A statLus improvement efforts in the future.The younger students should be considered as a priority group for intervention. |
