Mixed Linear Models Used for Repeated Measurement of Urine Iodine Level:Evidence from Children in Chongqing

To explore the variation of urine iodine level in daytime from children aged 8～10,so as to provide evidence for unifying the sampling time,urine samples from 60 pupils were collected in early morning,at 10:00 am,12:30 and 4:00 pm respectively.Those samples were then detected by spectrophotometric ceric-arsenic assay to measure the urine iodine.Mixed linear models were used to deal with the urine iodine data.The results whows that there were significant differences among urine iodine levels from various age groups and time points.The urine iodine level from 10:00 am and early morning urine shared similarities.It is feasible to use the 10:00 am urine sample instead of morning urine sample by multiplying correction factors as 1.094,0.997 and 1.072.Mixed linear models can effectively deal with repeated measurement data.