Preplanned Studies: Serum Vitamin A Nutritional Status of Children and Adolescents Aged 6−17 Years — China, 2016−2017

Vitamin A deficiency (VAD) has an important impact on the health of children and adolescents during the time of growth and development. VAD may damage the functioning of visual rod cells, reduce the ability of dark adaptation, and subsequently affect the visual function of children. Eye diseases, secondary to xerophthalmia caused by severe VAD in children, is a major cause of blindness in children worldwide, resulting in irreversible visual impairment in children. Various studies (1-2) have indicated that VAD, as an independent risk factor for respiratory diseases, may lead to the weakening of immune function in children, as well as recurrent respiratory infections and asthma. Furthermore, VAD may also cause anemia, dysplasia, and other diseases.

It is reported that there are still 190 million preschool children in the world with VAD (3). At present, there are about 228 million children with VAD in the world, which causes about 3 million children to die every year, and 10 million children suffer from eye diseases (4). Since 2002, serum retinol concentration has been used for the first time to evaluate the vitamin A nutritional status of children aged 3–12 years in China Nutrition and Health Survey. The serum retinol concentration was determined using high performance liquid chromatography (HPLC). In accordance with the National Health Standard (method for VAD screening) from the National Health Commission of the People’s Republic of China (5): serum retinol concentration <0.2 mg/L (0.70 μmol/L) is VAD, and 0.2 mg/L (0.70 μmol/L)≤ serum retinol concentration <0.3 mg/L (1.05 μmol/L) is marginal VAD.

This study was a cross-sectional study. Data were obtained from the China Nutrition and Health Surveillance of Children and Lactating Mothers in 2016–2017. It was conducted using multistage stratified random sampling method, including 31 provinces, autonomous regions and municipalities in the mainland of China, 150 monitoring sites, and 280 children and adolescents aged 6–17 years from each monitoring site with a sex ratio of 1∶1 (6). According to the 2018 China Health Statistics Yearbook, the regions are divided into eastern, central, and western regions. The protocol of this study was evaluated and approved by the ethical committee of China CDC (201614).

The study population was divided into different groups by gender, age, and regions. Data analyses used data from China’s Sixth National Census in 2010 with complex weights used in the calculation of rates for sampling. Values were presented as median (25th and 75th percentile) and percentages with their 95% confidence intervals (CIs) for continuous and categorical variables, respectively. Kruskal-Wallis one-way analysis of variance (ANOVA) was used to compare continuous data (such as serum retinol levels) among multiple groups. Rao-Scott chi-square analysis was used to compare categorical data (such as deficiency rates) between different groups. Statistical significance was defined as P<0.05. SAS 9.4 (SAS Institute Inc., Cary, NC, USA) was used to conduct all the analyses.

In total, 63,310 subjects were included for this report, including 31,617 male and 31,693 female with a gender ratio of 1.00. The number of urban and rural subjects were 29,532 and 33,778, respectively. The number of subjects aged 6–11 years and 12–17 years were 35,242 and 28,068, respectively.

Among 63,310 children and adolescents aged 6–17 years, the median of serum vitamin A was 1.35 μmol/L. The median of serum vitamin A in male and female were 1.35 μmol/L and 1.36 μmol/L, respectively. Although the median for female was higher than that of male, the difference was not significant. The median of serum retinol in individuals in urban areas (1.40 μmol/L) was significantly higher than that of those in rural areas (1.31 μmol/L). The median of serum retinol was 1.36 μmol/L, 1.27 μmol/L, and 1.40 μmol/L in the eastern, central, and western regions, respectively. The western region was significantly higher than the other two regions. The 6–11 age group was significantly lower than the 12–17 age group. (Table 1)

The results of VAD and marginal VAD in children and adolescents aged 6–17 years were illustrated in Table 2. The prevalence of VAD in children and adolescents aged 6–17 years was 0.96%, and the marginal VAD was 14.71%. There was no difference in the prevalence of marginal VAD between male and female, but the prevalence of VAD of male was higher than that of female (χ²=3.895, P=0.048). The prevalence of VAD among rural children and adolescents was higher than that of urban areas (χ²=20.615, P<0.0001). The prevalence of VAD was the lowest in the western region (χ²=43.649, P<0.0001). Similar phenomena were also found in the marginal deficiency group. The prevalence of marginal VAD of 6–11 year-old children was significantly higher than that of 12–17 year-old adolescents, which were 21.14% and 8.82%, respectively (χ²=585.378, P<0.0001). VAD was also higher in the 6–11 age group than in the 12–17 age group.