Participant recruitment
Children between 6 months and 18 years old attending physical examinations at the third Xiangya Hospital of Central South University, Changsha, Hunan, during January 2013 and April 2020, were recruited in this study (n=100997). Firstly, we eliminated participants who did not underwent anti-HBs detections (n=56181) or defined as positive in HBsAg test (n=57) before further analysis. Thereafter, we established precise inclusion criteria for the remaining candidates having negative HBsAg (n=44759) to generate valid subjects. Herein, participants lacking of essential information such as Gender, Age, way of birth, BMI, hemoglobin, Lead, Cadmium, Zinc, Copper, Calcium, Iron, WBC, VitD, C3, C4, IgA, IgG, IgE, IgM (n=9180) were not eligible. After which, individuals who were low birth weight (<2500 g, n=242), premature (<37 weeks, n=430), combined with diseases which might effect the response level of immunization, such as organic disease related to heart, lung, liver and kidney, allergic disease including asthma, anaphylactoid purpura and other immunological diseases (n=556) were excluded. Next, we filtered subjects failing to follow the obligational hepatitis B vaccination plan (n=10887), where children would be vaccinated within 24 hours, 1 month and 6 months (n=10887) as well as having revaccination before this physical examination (n=15150). Then we obtained further information of mentioned participants (n=8314), including duration of lactation period, history of eczema, frequency of cold and exposure to second-hand cigarette smoke by telephone follow-up. Herein, subjects who were unable to provide precise and complete data ascribed to memory bias or loss to follow-up (n=1206) were eliminated. Then we excluded participants whose mother had ever been infected with hepatitis B before delivery or given hepatitis B immune globulin at birth (n=1270) before. The final candidates (n=5838) were divided into an anti-HBs-positive group (n=3824) and an anti-HBs-negative group (n=2014) (Figure 1). This research was approved by the ethics committee of the third Xiangya Hospital of Central South University and in accordance with medical ethics. Parental consent in person was achieved for participants under 18 years old.
Statistics reference
The references for statistics were illustrated in Table 1 and Table 2, including status of anemia, body mass index, level of microelements, such as, Cu, Ca, Mg, Fe, Zn, Pb, Cd and the classification standard for division of subjects referring to the amount of anti-HBs. Because there is no unified BMI standard for children under 6 years old, we don’t discuss it in this paper. We applied the standard of inhalation of environmental tobacco smoke as the definition of being exposed to SHS[17] and more than 6 colds per year as a definition of frequent colds.
Table 1
The statistic reference of indicators.
|
Indicator
|
statistic reference
|
Anemia
|
7~59 months old
|
<110 g/L
|
5~11 years old
|
<115 g/L
|
12~14 years old
|
<120 g/L
|
Standards of microelements
|
Cu
|
11.8~39.3 μmol/L
|
Ca
|
1.55~2.10 mmol/L
|
Mg
|
1.12~2.06 mmol/L
|
Fe
|
7.52~11.82 mmol/L
|
Zn |
0~0.99 years old
|
58~100 μmol/L
|
1~1.99 years old
|
62~110 μmol/L
|
2~2.99 years old
|
66~120 μmol/L
|
3~4.99 years old
|
72~130 μmol/L
|
≥5 years old
|
76.5~150 μmol/L
|
Pb
|
0~100 μg/L
|
Cd
|
0~5 μg/L
|
Intoxication levels |
Pb
|
>100 μg/L
|
Cd
|
>2.5 μg/L
|
Anti-HBs |
Positive
|
>10mIU/mL
|
Negative
|
≤10mIU/mL
|
Table 2
The statistic reference of BMI.
Age
|
Normal BMI range
|
Male
|
Female
|
6~6.99 years
|
13.1-17
|
12.7~17.3
|
7~7.99 years
|
13.3~17.4
|
12.9~17.7
|
8~8.99 years
|
13.5-18
|
13.1~18.4
|
9~9.99 years
|
13.7~18.5
|
13.5~19
|
10~10.99 years
|
14~19.2
|
13.9~19.9
|
11~11.99 years
|
14.5~20
|
14.5~20.8
|
12~12.99 years
|
15~20.9
|
15~21.8
|
13~13.99 years
|
15.5~21.7
|
15.5~22.7
|
14~14.99 years
|
16~22.4
|
16.2~23
|
15~15.99 years
|
16.8~23
|
17.1~23.4
|
16~16.99 years
|
17.5~23.5
|
17.6~23.7
|
17~18 years
|
18~24
|
18~24
|
The children whose BMI was lower than the reference range were considered as thin, while BMI was higher than reference range were considered as overweight.
Statistical analysis
Enumeration data were described by n (%). Measurement data meeting the criterion of a normal distribution were showed by means and standard deviations. All variables were processed by univariate logistic regression analysis, using odds ratios (ORs) and 95% confidence intervals (CIs) to assess the extent of the relevance. The variables which P value < 0.10 in the chi-square test and T test in any age subgroup were selected for univariate logistic regression analysis, then the variables which P value < 0.10 were selected for further multivariate logistic regression analysis for each age subgroup separately. All data were analysed through SPSS (IBM SPSS Statistics for Macintosh, Version 24.0, Armonk, NY: IBM Corp). P < 0.05 was considered statistically significant.