Participants and Procedures. This study was a secondary data analysis of the 2019 Mongolian GSHS data. The GSHS 10 core questionnaire modules address the leading causes/risk factors of morbidity and mortality among children: tobacco, alcohol, and other drug use; dietary behaviors; hygiene; mental health; physical activity; sexual behaviors that contribute to HIV infection, other sexually transmitted infections, and unintended pregnancy; unintentional injuries and violence; and respondent demographics. Students were asked to participate voluntarily in the survey, and written informed consent was obtained from each student and parents/guardians. The GSHS used a two-stage cluster sampling design where participants were given a self-reported questionnaire. The first stage, the probability of schools being selected was proportional to the number of students enrolled. The second stage, involved classes being randomly selected and all students in the selected classes were eligible to participate [17]. The Mongolian GSHS protocol was approved by Resolution No. 88 of the Ethical Committee of the National Center for Public Health in November 2018. Altogether 7149 students participated in the 2019 Mongolian GSHS survey.
Measures. With the exception of grade, all variables were dichotomized as yes or no/good or poor answers.
Oral hygiene as the dependent variable is based on the following question: “During the past 30 days, how many times per day did you usually clean or brush your teeth?” (Response options were 1 = Did not brush my teeth during the past 30 days, 2 = less than 1 time per day, 3 = 1 time per day, 4 = 2 times a day, 5 = 3 times a day and 6 = 4 or more times per day; coded 1–3 = poor oral hygiene was defined as brushing teeth less than two times per day and 4–6 = good oral hygiene when brushing 2 or more times per day).
The independent variables were demographic factors, hand hygiene behaviors, mental distress, substance uses, and health risk behaviors.
Demographic factors:
Gender
“What is your sex?” (Response options were 1 = male and 2 = female; coded 0 = male and 1 = female).
Grade
“Which grade are you study?” (Response options were 1 = 5th grade, 2 = 6th grade, 3 = 7th grade, 4 = 8th grade, 5 = 9th grade, 6 = 10th grade, 7 = 11th grade and 8 = 12th grade).
Hand Hygiene behaviors:
Handwashing before eating
“How often did you wash your hand before eating?” (Response options were 1 = never, 2 = rarely, 3 = sometimes, 4 = most of the time and 5 = always; coded 1–4 = no and 5 = yes).
Handwashing after toilet
“How often did you wash your hands after using the toilet or latrine?” (Response options were 1 = never, 2 = rarely, 3 = sometimes, 4 = most of the time and 5 = always; coded 1–4 = no and 5 = yes).
Handwashing with soap
“How often did you use soap when washing your hands?” (Response options were from “1 = never, 2 = rarely, 3 = sometimes, 4 = most of the time and 5 = always; coded 1–4 = no and 5 = yes).
Mental Distress:
Being bullied: “During the past 30 days, on how many days have you been bullied?” (Response options were 1 = 0 day, 2 = 1 or 2 days, 3 = 3 to 5 days, 4 = 6 to 9 days, 5 = 10 to 19 days, 6 = 20 to 29 days and 7 = All 30 days; coded 1 = no and 2–7 = yes). [Description provided in the questionnaire: Bullying occurs when one or more students or someone else about your age teases, threatens, ignores, spreads rumors about, hits, shoves, or hurts another person over and over again].
Close friend
“How many close friends do you have?” (Response options were 1 = 0 friend, 2 = 1 friend, 3 = 2 friends and 4 = 3 or more; coded 1 = no and 2–4 = yes).
Substance use:
Cigarette smoking
“During the past 30 days, how many days have you smoked cigarettes?” (Response options were 1 = 0 day, 2 = 1 or 2 days, 3 = 3 to 5 days, 4 = 6 to 9 days, 5 = 10 to 19 days, 6 = 20 to 29 days and 7 = All 30 days; coded 1 = no and 2–7 = yes).
Exposed to second-hand smoke
“During the past 7 days, on how many days did people smoke in your presence?” (Response options were 1 = 0 day, 2 = 1 or 2 days, 3 = 3 or 4 days, 4 = 5 or 6 days and 5 = all 7 days; coded 2–5 = yes and 1 = no)
Alcohol drinking
“During the past 30 days, on how many days have you had at least one drink containing alcohol?” (Response options were 1 = 0 day, 2 = 1 or 2 days, 3 = 3 to 5 days, 4 = 6 to 9 days, 5 = 10 to 19 days, 6 = 20 to 29 days and 7 = All 30 days; coded 1 = no and 2–7 = yes).
Health risk behaviors:
Physical activity: “During the past 7 days, on how many days were you physically active for a total of at least 60 min per day?” (Response options were 1 = 0 day, 2 = 1 day, 3 = 2 days, 4 = 3 days, 5 = 4 days, 6 = 5 days, 7 = 6 days and 8 = 7 days; coded 1 = physically inactive and 2–8 = physically active)
Sedentary behavior
“How much time do you spend during a typical or usual day sitting and watching television, playing computer games, talking with friends, or doing other sitting activities?” (Response options were 1 = Less than 1 hour per day, 2 = 1 to 2 hours per day, 3 = 3 to 4 hours per day, 4 = 5 to 6 hours per day, 5 = 7 to 8 hours per day and 6 = more than 8 hours per day; coded 3–6 = yes and 1–2 = no).
Data Analysis. Data analysis was carried out with IBM SPSS (Statistical Package for the Social Sciences) version 28 (SPSS Inc., Chicago, IL, USA). Descriptive statistic was done to describe the study sample; distributions were calculated according to the number of current answerers. Univariable logistic regression analyses were conducted to examine unadjusted associations between oral hygiene and independent variables. Multivariable logistic regression analysis was used to assess the independent contribution of demographic factors, hand hygiene behaviors, mental distress, substance uses, and health risk behaviors to poor oral hygiene. The independent variables involved in the regression analysis were student gender, grade, and hand hygiene behaviors including handwashing before eating, handwashing after toilet and handwashing with soap, being bullied, having no close friends, cigarette smoking, exposure to second-hand smoke, alcohol drinking, being physically inactive, and sedentary behavior. The student’s grade was considered as a continuous variable in the model. Odds ratio (OR) and 95% CI of OR were used to indicate the association between the oral hygiene and the selected independent variables. Statistical significance was defined at p < 0.05.