CHAPTER 2 2. METHODOLOGY 2.1 Objectives 2.1.1 General objective To examine the prevalence of overweight and obesity of Singapore Chinese children aged 6 to 72 months using three different criteria; “CDC BMI for age”, “IOTF BMI for age” and “Singapore BMI for age” references. 2.1.2 Specific objectives (1) To compare the prevalence of overweight and obesity between boys and girls (2) To compare the variation of overweight and obesity by age groups (3) To evaluate the associations between overweight/obesity with potential risk factors such as birth weight, duration of preschool hours per day, physical activities (playing outdoors, leisure activities), sedentary activities (watching television, playing computer/television/hand held video games, reading, drawing and coloring activities), socioeconomic status (father’s education, mother’s education, total combined monthly income), presence of park or garden near to home, breastfeeding, types of breastfeeding, maternal smoking and alcohol consumption during pregnancy. 34 2.1.3 Hypothesis for Risk Factors From the literature review, we hypothesized that overweight, obesity or combined overweight and obesity is potentially associated with the following risk factors: (i) birth weight, (ii) physical activities (playing outdoors, leisure activities), sedentary activities (watching television, playing computer/television/hand held video games, reading, drawing and coloring activities), (iii) socioeconomic status (father’s education, mother’s education, total combined monthly income), (iv) breastfeeding, types of breastfeeding, maternal smoking and alcohol consumption during pregnancy. (v) other factors: duration of preschool hours per day, presence of park or garden near to home. 2.2 Study Design and Study Population 2.2.1 Study Design It is a cross-sectional study which is part of “A Study on Strabimus, Amblyopia and Refractive Error in Singapore Chinese Preschoolers (STARS)”. 35 STARS is a population based cross-sectional study to determine the prevalence of eye diseases (mainly myopia, strabismus and refractive error) in 3,000 Chinese children aged 6–72 months in Singapore. The STARS study was conducted from February 2006 to November 2008. 2.2.2 Study area and Study population The study areas were South-Western part of Singapore (Bukit Batok, Clementi and Queenstown) and Western parts of Singapore (Jurong East and Jurong West) of Housing Development Board (HDB) apartments. These parts of Singapore were chosen because they are close to the Singapore Eye Research Institute and Jurong Medical Centre where the subject assessment and measurements took place. Chinese children aged between 6–72 months living in this study area were our study subjects. In Singapore, the total resident population is 3.7 million in which there are 410,107 children (10.8%) aged below 9 years.73 The total resident population in our study areas (South-Western and Western parts of Singapore) is 690,216 and children below 9 years old constitutes 10.9% (75,528).73 Children aged below 1 year constitute 0.9% [n=32,788; boys=16,693 (50.9%), girls=16,095 (49.1%)] in 3.7 million Singapore resident population, compared to our study in which children aged 6 months to below 1 year is 0.03% [n=181; boys=85 (47.0%), girls=96 (53.0%)]. Moreover, of which 3.7 million resident population, the proportion of children aged 1 year is 1.0% [n=38,350; boys=19,549 (51.0%), 36 girls=18,801 (49.0%), aged 2 years is 1.1% [n=41,562; boys=21,049 (50.6%), girls=20,513 (49.4%)], aged 3 years is 1.1% [n=40,869; boys=20,853 (51.0%), girls=20,016 (49.0%)], aged 4 years is 1.1% [n=40,863; boys=20,746 (50.8%), girls=20,117 (49.2%)] and aged 5 years is 1.1% [n=40,915; boys=20,755 (50.7%), girls=20,160 (49.3%)].73 In our study, aged 1 year constitutes 0.08% [n=527; boys=304 (57.7%), girls=223 (42.3%)], aged 2 years constitutes 0.07% [n=509; boys=257 (50.5%), girls=252 (49.5%)], aged 3 years constitutes 0.08% [n=571; boys=291 (51.0%), girls=280 (49.0%)], aged 4 years constitutes 0.09% [n=601; boys=321 (53.4%), girls=280 (46.6%)] and aged 5 years constitutes 0.08% [n=575; boys=290 (50.4%), girls=285 (49.6%)]. A total of 5,648 preschool children aged 6–72 months were recruited from households in South-Western and Western areas of Singapore and 3,009 (72.2%) children responded. 2.2.3 Sampling method All households located in the South-Western (Bukit Batok, Clementi, and Queenstown) and Western (Jurong East and Jurong West) part of Singapore with Chinese children aged 6–72 months formed the sampling frame. Disproportionate stratified random sampling by 6 month age groups was performed. To obtain a high response rate and obtain a target sample size of 3,000, total 5,648 children of aged between 6–72 months were recruited. 37 The approval to conduct the study was obtained from the Institution Review Board (IRB) from Singapore National Eye Centre and Domain Specific Review Board (DSRB) from National Health Group. 2.2.4 Inclusion and Exclusion Criteria Children were eligible if they were aged between 6 months to 6 years and Chinese in which at least one of the parents of the child must be Chinese. Exclusion criteria included children aged over 6 years or non-Chinese or children with chronic diseases, children with relevant disabilities or children with congenital abnormalities. If the family moved out from this address or the given address was an error, the child was ineligible. Of the 5,648 participants, 4,164 of children were eligible for the study. Eligible group was divided into refused, non-contactable and attended groups. Children were categorised as refused (n=1,119) if the parents were not interested to take part in the study, too-busy, had no time or they could not attend because they thought that the clinics were far from their home. Non-contactables (n=36) were defined as those who could not be contacted at least 8 times. The attended group includes 3,009 participants. Ineligible category includes overage or underage (612 children). 384 children were ineligible because the family moved out. Races other than Chinese were also under the ineligible group of “Non-Chinese” subset, and it constituted 38 37 children. Data error (n=152) was also included in the ineligible group, and other unknown reason of ineligibility included 299 children. 2.3 Recruitment 2.3.1 Recruitment chart Sampling Frame (n=5,648) Eligible (n=4,164) Ineligible (n=1,484) Refused Non- Attended (n=1,119) Contactable (n=3,009) 26.9% (n=36) 72.3% 0.8% Overage/ Underage (n=612) 41.2% Moved (n=384) NonChinese 35.8% (n=37) Data error Others (n=152) (n=299) 10.3% 20.2% 2.5% 39 2.3.2 Recruitment Process Brochures of STARS and the invitation letters of both English and Chinese language were sent out to all the households. The invitation letter described common eye diseases in preschool Chinese children, the objective of this survey and invitation to participate in this survey. Parents who were interested in the survey called back and made an appointment at one of the two clinics. For those who did not call back, the door-to-door recruitment process was conducted and guided by recruitment officers. During the home visit, the recruiters explained the objective of STARS and the processes (eye examination after putting eye drops, interview questionnaire about the child’s life style and quality of life) which they will be encountered during the survey. The explanation was either in the English or Chinese language depending on the subject’s preference. The recruiter also explained about the possible risks of eye drops (mild local allergic reactions, slight temporary difficulty or blurring of vision in reading and mild discomfort while looking at bright lights for 1 to 2 days) which was used to dilate pupils for eye examination. If the parents were interested in the study and agreed to bring their child for the survey, the recruiters arranged appointments for them at one of the two clinics. 40 2.3.3 Clinic Visit Registration Taking informed consent Eye examination 1. 2. 3. 4. 5. 6. 7. Glasses Stereopsis Accommodative lag Bruckner Test Eye alignment Ductions Fixation Preference test 8. Color vision 9. Visual acuity 10. Anterior segment evaluation 11. Ocular Dominance Putting Eye drops (30 minutes waiting time) Interview Questionnaire Measuring Height and Weight Eye examination 1. Biometry (>30months) 2. Autorefraction (>24months) or Retinomax (47months) Give Report and End the survey 41 2.3.4 Clinic Visit and Ethics consideration The children were registered and the qualified optometrist of the survey team explained about the risks and benefits of this survey they participated. The parents of the participants were also explained about the confidentiality and autonomy with their child in the whole survey process. If the parents agreed to the survey procedures, they were asked to sign the informed consent form for behalf of their child. A copy was given to the parents, and another was kept for the study. Even the parents refused to continue participating in the research process, the refusal was respected and the whole entire process of the survey was stopped. 2.4 Height and Weight Measurements Weight was measured in kilograms (kg) to the nearest one decimal point, and height was measured in centimeters (cm) to nearest one decimal point. Recruiters who were assigned as examiners in height and weight measurements were trained to perform the same standardized measurement procedures by an experienced general practitioner. The equipments (Seca model 220) used for measuring height and weight for children 2 years old and above, were calibrated once a year. 42 2.4.1 Measuring Height and Weight of Child 2 years old and above For a child 2 years of age and above who can stand without support, the column digital weighing scale with attached telescopic measuring rod (Seca-220) was used. The tar weighing function was set to zero the scale before each child was weighed. The child was wearing light clothings without shoes, heavy objects in the pockets, and hair accessories. The child was instructed to stand still in the middle of the scale platform, with arms relaxed and hanging down by the side of the body, both feet slightly apart in order to distributed the weight equally. Height was measured using the same machine. The child was asked to look straight ahead along the Frankfort Plane. The Frankfort plane is the line connecting the superior border of the external auditory meatus with the lower edge of the eye. The measuring slide of the telescopic rod was moved in horizontal position till it firmly abut the crown of the head, slightly compressing the hair, without bending the slide. The height is noted at the read off mark. Accuracy of measurement better than +/- 5 mm can be achieved according to the manufacturer. 2.4.2 Measuring Height and Weight of Child less than 2 years If the child is less than 2 years old, or unable or unwilling to stand unsupported on the scale, the child was measured in the parent’s arms. The parent was weighed alone, and then weighed again with child in arms. The combined 43 weight of parent and child was recorded, and the actual weight of the child was obtained by subtracting these two measurements. The supine length measurement was taken with the Kiddimeter (a recumbent length board for infant with a fixed head board and movable footboard), placed on a sturdy table. The accuracy of the Kiddimeter is 1 mm according to the manufacturer (Raven Equipment, Castlemead, UK). First, the child was placed with his face upward and with the body parallel to the long axis of the board. One examiner brought the child’s head gently to contact with the fixed headboard. The second examiner held the child’s feet and toes perpendicular to the measuring length board, keeping the knees straight and bringing the moveable footboard against the heels. If the child was restless, only one leg was positioned for the measurement. 2.5 Skinfold Measurements For child who is 2 years old and above, subcutaneous fat thickness was measured using the Holtain skinfold caliper. This caliper was designed to give a constant pressure of 10gms/sq.mm according to manufacturer and marked in divisions of 0.2mm, starting from 0 mm up to 40 mm. The dial of the caliper was checked to ensure at zero each time before use. Only the triceps site was measured in the study. The right arm was used for this skinfold measurement. The child was asked to stand, with back facing the examiner with the arms were relaxed. Mid44 way between tip of acromion and the tip of the olecranon process, a fold of skin, deep enough to get the subcutaneous fat but without picking the triceps muscle was lifted perpendicularly to the surrounding skin with the thumb and forefinger of the examiner’s left hand. The calipers were applied to the fold midway between the crest and the base of the fold, maintaining this fold throughout the measuring process. The reading was noted down and the process was repeated another two times to obtain three measurements at the same site. An average value was obtained. 2.6 Questionnaire The questionnaire in this study was administered by well-trained interviewers of our research team. The questionnaire was adapted and modified from both the SCORM (Singapore Cohort Study of the Risk Factors for Myopia)74 and the quality of life questionnaire of MEPEDS (The Multi-Ethnic Pediatric Eye Disease Study)75. The questionnaire includes family history, birth weight, duration of preschool hours, physical activities, sedentary activities, presence or absence of park or garden near to home, maternal smoking and alcohol consumption history during pregnancy, types of breastfeeding in breastfed mother. Before proceeding with the interview questionnaire to a parent or guardian, the interviewer assured the confidentiality of the information, which was answered by the parent or guardian, and we respected any refusal to answer 45 any of the questions if they do not want. Informed consents were obtained from the parents or guardians. The questionnaire took about half an hour to complete. For those parents or guardians who are not conversant with the English language, the interviewer used the Chinese language version of the questionnaire. 2.6.1 Family History 2.6.1.1 Income The total income per month of the family were asked for (“What is your total combined monthly household income? [Singapore dollars]”), by interviewing either the father or mother, and classified into four categories: Less than S$1,000, S$1,000–S$2,999, S$3,000–S$4,999, S$5,000 and above. There were also ‘Refuse’ and ‘Don’t know’ categories for that question if either father or mother did not want to answer, or could not estimate the actual the total combined monthly income. 2.6.1.2 Education of parents Educational level of father (“What’s the child father’s completed educational level?”) was classified into seven categories: None, Primary, Secondary, “O”/”N” levels, “A” levels/Polytechnic/Diploma/ITE/Certificate, University education (degree and above, including bachelor, master and PhD) and 46 Others. If the educational level was chosen as ‘Others’, it was specified and recorded. Similarly with the total combined monthly income, there were also ‘Refuse’ and ‘Don’t know’ categories for that question if the child’s father did not want to answer his/her education, or did not know which category fit in his educational level. The educational level of mother (“What’s the child mother’s completed educational level?”) was also asked as the same way as the father’s education status. 2.6.2 Clinic Questionnaire 2.6.2.1 Birth Weight The parents were asked to bring the child’s health booklet on the appointment day. From the health booklet, the information of the child’s birth weight was recorded in grams as an answer to the question “How much did your child weigh at birth?” If the parents cannot remember their child’s birth weight, ‘Don’t know’ category for that question was selected. There was also ‘Refuse’ category for those parents did not want to answer that question. 2.6.2.2 Preschool Hours Many children in Singapore attend pre-nursery (3 years old and younger), nursery (4 years old), kindergarten 1st year (5 years old) and kindergarten 2nd year 47 (6 years old) before they enter primary schools. If the child was attending one of these preschools, the duration of time in preschool was asked by “How many hours per day does your child spend in pre-school?” 2.6.2.3 Physical Activities 2.6.2.3.1 Playing outdoors The interviewer asked for the number of hours per day on weekdays (outside of regular school hours) during which the child played outdoors, such as walking and biking. Similarly, this same question was asked for weekends. If the child was too young to play outdoors, ‘Not applicable’ category was selected. If the parents could not estimate the actual activities of the child, ‘Don’t know’ category was chosen and if the questions were refused by the parents, ‘Refused’ category was ticked. The weighted variable of ‘Playing outdoors’ was calculated as follows: Playing outdoors= (time hours of playing outdoors per day in weekdays playing outdoors per day in weekends x x 5/7) + (time hours of 2/7) 2.6.2.3.2 Leisure Activities The time spent on leisure activities (hours per day) such as going to park, beach or picnic for weekdays and weekends (separately, as described above), 48 outside the regular school hours, was asked. There were also ‘Don’t know’ and ‘Refused’ categories if the parents could not estimate the actual activities of the child or if the questions were refused by the parents, respectively. The weighted variable of ‘Leisure activities’ was calculated as follows: Leisure activities= (time hours of leisure activities per day in weekdays x 5/7) + (time hours of leisure activities per day in weekends x 2/7) 2.6.2.4 Sedentary Activities 2.6.2.4.1 Watching Television The hours of watching television per day in weekdays as well as in weekends were asked separately (as described above). There were ‘Not applicable’ category for which if the child was too young to watch television, ‘Don’t know’ category for which if the parents could not estimate about it and ‘Refused’ category for which if the parents did not want to answer that question. The weighted variable of ‘Watching television’ was calculated as follows: Watching television= (time hours of watching television per day in weekdays x 5/7) + (time hours of watching television per day in weekends x 2/7) 2.6.2.4.2 Playing television/computer/hand held video games In the questionnaire, time spent playing games (television/computer/hand held video) was also asked as hours per day for both weekdays and weekends, 49 separately. If the child was too young to play these games, ‘Not applicable’ category was selected. The weighted variable of ‘Playing television/computer/hand held video games’ was calculated as follows: Playing television/computer/hand held video games = (time games per day in weekdays+ time hours of playing television hours of playing computer games per day in weekdays hand held video games per day in weekdays + time hours of playing x 5/7) + (time hours of playing television games per day in weekends + time hours of playing computer games per day in weekends + time hours of playing hand held video games per day in weekends x 2/7) 2.6.2.4.3 Reading, drawing and coloring The hours per day of reading, writing (for school work and read for pleasure) and coloring or drawing for fun in weekdays and weekends were also asked separately in the questionnaire. The weighted variable of ‘Reading and writing, coloring or drawing’ was calculated as follows: Reading and writing, coloring or drawing = (time weekdays+ hours of reading and writing per day in time hours of coloring or drawing per day in weekdays x 5/7) + (time hours of reading and writing per day in weekdays+ time hours of coloring or drawing per day in weekdays x 2/7) 50 2.6.2.4.4 Total sedentary activities In our study, watching television, playing television/computer/hand held video games, reading, drawing and coloring were combined and regarded as total sedentary activities. The weighted variable of ‘Total sedentary activities’ was calculated in the following expression: Total sedentary activities = (time playing television games per day in weekdays+ hours of watching television per day in weekdays hours of coloring or drawing per day in weekdays) weekends hours of time hours of playing computer games per day in weekdays + time hours of playing hand held video games per day in weekdays+ time + time time hours of reading and writing per day in weekdays+ x 5/7 + (time hours of watching television per day in + time hours of playing television games per day in weekends + time hours of playing computer games per day in weekends + time hours of playing hand held video games per day in weekends + time hours of reading and writing per day in weekdays+ time hours of coloring or drawing per day in weekdays ) x 2/7 2.6.2.5 Presence of park or garden near home To assess the presence of park or garden near to the child’s home, the question of “Is there a park or garden near to your home where your child could play outdoors?” was asked. However, the question was not defined for the distance to park or garden. The answers provided for this question were ‘Yes’, ’No’, ‘Refused’ and ‘Don’t know’. If the family lives near park or garden, ‘Yes’ category was selected. If there was no park or garden near to their home, ‘No’ category was chosen. 51 2.6.2.6 Maternal smoking and alcohol consumption during pregnancy History of maternal smoking and alcohol consumption during pregnancy were assessed separately (“At any time during the pregnancy with the child, did you smoke?” and “At any time during the pregnancy with the child, did you drink alcohol?”). There were options of ‘Yes’, ’No’, ‘Refused’ and ‘Don’t know’ as answers for each question. 2.6.2.7 Breastfeeding Regarding breastfeeding questionnaire, the mother was asked “Was your child ever breastfed or fed breast milk?” and if she replied she did, the rest of the questionnaire regarding breastfeeding were continued. If she replied the answer of ‘No’ or ‘Don’t know’, the questionnaire regarding breastfeeding were skipped and proceeded to others. If the mother breastfed the child, the interviewer asked the question of “How long did you breastfeed this child?” There were 7 categories to answer: ‘less than 1 week’, ‘1 to 4 weeks’, ‘1 to 3 months’, ‘4 to 6 months’, ‘6 to 12 months’, ‘More than 12 months’ and ‘Still breastfeeding’. Types of breastfeeding were also assessed by asking the mother “Which type of breastfeeding best describes what you practiced/received at that time?” The answers provided for this question were ‘Exclusive breastfeeding’, ‘Mostly breastfeeding’ and ‘Partly breastfeeding’. If the child only received breast milk (may include medicines and 52 vitamins), ‘Exclusive breastfeeding’ category was selected. If the mother fed her child with breast milk and water, sweetened water, or juices but not formula milk, the interviewer selected ‘Mostly breastfeeding’ category. However, if the child received formula milk or other complementary foods in addition to breast milk, it was regarded as ‘Partly breastfeeding’. 2.7 Referral If there was a pathologic eye condition or high/low blood pressure detected which needed medical attention, a referral letter to the ophthalmologist or general practitioner was given to the caregiver to seek appropriate treatment. A gift was given to the child and incentives were given to the parents in appreciation of their participation. The completed case files were transferred to the survey office for data entry and management. 2.8 Data Management For the safety of data and confidentiality, the participating children were identified by their specific identification numbers which were set up in the database and in all the forms relating to subjects. Moreover, the password to access the study data files was only given to the staff in the survey team. To facilitate data entry from measurements, pre-coding was done. Microsoft access 2003 was used to setup the database. 53 Four members of the STARS team were designated to enter data into the database. After double data entries, data were checked for inconsistencies between the first and second data entry by using specified software. If there was a mismatch, we checked which variable was involved and the study ID was noted. The file was searched according to study ID and the variable of mismatch was checked with the data inside the case file. The correct data was noted and corrected in the database. 2.9 Data Analysis Among 3,009 participants, data of 2,964 participating children were involved in the analysis after dropping the missing values and excluding two participating children with extreme values of BMI above 90 kg/m2 which are assumed as errors during taking measurements or recording the data. 2.9.1 Definitions of overweight and obesity BMI was calculated as weight in kilograms divided by height in meters squared (kg/m2). To compare the prevalence of overweight and obesity, using three different criteria, we analysed the BMI data, according to (1) the CDC reference which defines a BMI above 95th percentile for age as “overweight” and that of above 85th percentile for age as “at-risk-for-overweight”, (2) the IOTF reference which defines overweight/obesity as above the extrapolated percentile lines which intersect the adult cut-off points of BMI of 25kg/m² and 30kg/m2 at 54 age 18 year as overweight and obesity, respectively, and (3) the “Singapore BMI for age” reference which defines BMI at and above 90th to 97th percentile for age as “overweight”, and above 97th percentile for age as “obese”. At the time of writing this thesis, the Health Promotion Board of Singapore has not defined childhood overweight and obesity using this BMI percentile chart yet. Unfortunately, this BMI for age chart does not have the 85th and 95th percentile lines. Thus, we decided to arbitrarily us the 90th and 97th percentile curves (which are plotted in this chart) to define overweight and obesity for this study. Although the CDC used the terms “at-risk-for-overweight” and “overweight”, “overweight” and “obesity” terms were only used in this study to standardize for all three criteria. In the analysis of associations, the weight statuses of the children (overweight and obese) were used as dependent variables and relevant familyrelated and behaviour-related determinants were independent variables. We compared “overweight” category with “Not overweight/obese” which includes normal weight as well as underweight children but excludes obesity. Moreover, as for “obesity”, we compared it with “Not overweight/obese” category, excluding the “overweight” category. This study also combined overweight and obesity to create the category of “Overweight/Obesity” and also compared with the category “Not overweight/obese” for the association analysis. 55 2.9.2 Statistical analysis All variables used in the analysis were changed to categorical data to facilitate interpretation. The χ²-test was used to evaluate the difference between two groups of potential variables of interest according to the outcome. However, if the variables of interest were categorised into more than two groups (age groups, quartiles groups and categories of parental education, total monthly income and types of breastfeeding), the differences among the groups were analysed by using one-way ANOVA test. The χ2-trend test was used to assess trends in the prevalence of overweight and obesity. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated. Means were compared using ttests. Statistical significance was set at 0.05 and SPSS 17.0 software was used to compute all the analyses. 2.9.3 Construction of multiple regression models Among the variables of interest, only the potential variables with statistically significance value less than 0.02 based on the results of univariate analysis were placed in our multivariate models. Age, gender and father’s educational level were introduced into the models as confounders. The categorical variable of ‘father’s educational level’ was converted in dichotomous dummy variable. In the multivariate linear regression analysis, BMI (kg/m2) was used as the dependent variable. Birth weight, duration of preschool hours per day and 56 duration of watching television hours per day were used as independent variables, and age, gender and father’s education were adjusted in this model. In the multivariate logistic regression analysis, combined overweight and obesity (‘Overweight/Obesity’) was used as the dependent variable and birth weight and duration of total sedentary activities per day were independent variables, and age, gender and father’s education were adjusted. 57 [...]... in the questionnaire The weighted variable of ‘Reading and writing, coloring or drawing’ was calculated as follows: Reading and writing, coloring or drawing = (time weekdays+ hours of reading and writing per day in time hours of coloring or drawing per day in weekdays x 5/7) + (time hours of reading and writing per day in weekdays+ time hours of coloring or drawing per day in weekdays x 2/ 7) 50 2 .6. 2. 4.4... pre- nursery (3 years old and younger), nursery (4 years old) , kindergarten 1st year (5 years old) and kindergarten 2nd year 47 (6 years old) before they enter primary schools If the child was attending one of these preschools, the duration of time in preschool was asked by “How many hours per day does your child spend in pre- school? ” 2 .6. 2. 3 Physical Activities 2 .6. 2. 3.1 Playing outdoors The interviewer asked... time hours of playing x 5/7) + (time hours of playing television games per day in weekends + time hours of playing computer games per day in weekends + time hours of playing hand held video games per day in weekends x 2/ 7) 2 .6. 2. 4.3 Reading, drawing and coloring The hours per day of reading, writing (for school work and read for pleasure) and coloring or drawing for fun in weekdays and weekends were... hours of playing computer games per day in weekends + time hours of playing hand held video games per day in weekends + time hours of reading and writing per day in weekdays+ time hours of coloring or drawing per day in weekdays ) x 2/ 7 2 .6. 2. 5 Presence of park or garden near home To assess the presence of park or garden near to the child’s home, the question of “Is there a park or garden near to your home... data was noted and corrected in the database 2. 9 Data Analysis Among 3,009 participants, data of 2, 964 participating children were involved in the analysis after dropping the missing values and excluding two participating children with extreme values of BMI above 90 kg/m2 which are assumed as errors during taking measurements or recording the data 2. 9.1 Definitions of overweight and obesity BMI was... day in weekdays hours of coloring or drawing per day in weekdays) weekends hours of time hours of playing computer games per day in weekdays + time hours of playing hand held video games per day in weekdays+ time + time time hours of reading and writing per day in weekdays+ x 5/7 + (time hours of watching television per day in + time hours of playing television games per day in weekends + time hours of. .. percentile lines which intersect the adult cut-off points of BMI of 25 kg/m² and 30kg/m2 at 54 age 18 year as overweight and obesity, respectively, and (3) the Singapore BMI for age” reference which defines BMI at and above 90th to 97th percentile for age as “overweight”, and above 97th percentile for age as “obese” At the time of writing this thesis, the Health Promotion Board of Singapore has not defined... The questionnaire took about half an hour to complete For those parents or guardians who are not conversant with the English language, the interviewer used the Chinese language version of the questionnaire 2 .6. 1 Family History 2 .6. 1.1 Income The total income per month of the family were asked for (“What is your total combined monthly household income? [Singapore dollars]”), by interviewing either the... 2 .6. 2. 4.4 Total sedentary activities In our study, watching television, playing television/computer/hand held video games, reading, drawing and coloring were combined and regarded as total sedentary activities The weighted variable of ‘Total sedentary activities’ was calculated in the following expression: Total sedentary activities = (time playing television games per day in weekdays+ hours of watching... calipers were applied to the fold midway between the crest and the base of the fold, maintaining this fold throughout the measuring process The reading was noted down and the process was repeated another two times to obtain three measurements at the same site An average value was obtained 2 .6 Questionnaire The questionnaire in this study was administered by well-trained interviewers of our research team ... (49 .6% )] A total of 5 ,64 8 preschool children aged 6 72 months were recruited from households in South-Western and Western areas of Singapore and 3,009 ( 72. 2% ) children responded 2. 2.3 Sampling method... (mainly myopia, strabismus and refractive error) in 3,000 Chinese children aged 6 72 months in Singapore The STARS study was conducted from February 20 06 to November 20 08 2. 2 .2 Study area and. .. households located in the South-Western (Bukit Batok, Clementi, and Queenstown) and Western (Jurong East and Jurong West) part of Singapore with Chinese children aged 6 72 months formed the sampling