Training
Porto, Portugal, 13-15 February 2008
WHO European Childhood Obesity
Surveillance Initiative
Trudy Wijnhoven
WHO Regional Office for Europe, Copenhagen
Part 1
 Background and objectives of the
surveillance system
 Introduction to protocol
 Ethical aspects
 Confidentiality of the data
Part 2
 Protocol
• Review in detail
• Questions and answers
Part 3
 Organization of the Country Coordination Team and
division of responsibilities
 Specific role of examiners
 Routing of data collection forms
 Standardization of conditions
 Support of children with anxieties
 Prevention of stigmatization and bullying
 Setting up the measurement session of the children
in a school
 Interaction with schools, children and parents
PART 1
Individual growth monitoring &
Nutritional surveillance
 Individual growth monitoring
• Collection of anthropometric data at the individual level
• Asses the need to refer this particular child to improve
growth and health (e.g. nutrition education, breastfeeding
support, supplementation, treatment underlying diseases,
physical activity education)
• Monitor individual growth pattern over time
 Surveillance
• Collection of anthropometric data at the population level
• Asses the prevalence of both under- and over-nutrition
for purposes of programme planning, implementation and
evaluation
• Monitor prevalence trends over time
Nutritional surveillance
 Continuous monitoring of the physical status
of a population, based on repeated surveys,
or on data from child health or growthmonitoring programmes
 Information on the prevalence of over- and
undernutrition is used to promote,
implement and evaluate programmes aimed
at improving health and nutritional status
Surveillance ≠ screening
 Screening means applying a test to or measuring a
defined group of persons in order to identify an
early stage, a preliminary stage, a risk factor or a
combination of risk factors of a disease – the
people who are found are then treated.
 A screening system aims to identify a certain
disease or risk factor for a disease before the
affected person spontaneously seeks treatment, in
order to cure the disease or prevent or delay its
progression or onset by early intervention.
Background
 Overweight in children is an increasing problem in
Europe
•
•
Associated with risk factors for cardiovascular disease,
diabetes, mental disorders, lower self-esteem
60% overweight before puberty remain overweight in
early adulthood
 Prevention is seen as most feasible option
 1/3 countries only expand routine growth
monitoring beyond age of 6 years
•
If countries do individual growth monitoring, often data
are not transferred to a national database
Overweight among schoolage children
in the WHO European Region
Germany: Aachen city, 2001-2002, 5-6
Cyprus, 2004, 2-6
Survey characteristics: country, year, age range
(years)
10.1
Boys
5.4
Serbia and Montenegro: North Backa region, 1995-2002, 6-10
3.9
5.7
10.3 11.3
4.4
Girls
4.5
11.2
6.9 4.9
11.4
7.6
9.1 9.8
6.7
8.7 12.6
4.2
2.4
Italy: Perugia, Terni and Rieti provinces, 1993-2001, 3-9
Slovakia, 2001, 7-9
4.9
Sweden, 2003, 4
7.4 9.9
10.5 11.7
Netherlands, 2005, 2-9
Greece, 2003, 2-6
15.2
4.0
Pre-obese, self- or
parent-reported
Obese, self- or
parent-reported
15.0 16.0
2.0
3.6
Overweight,
measured
France, 2000, 7-9
3.9
14.0 14.7
Norway, 2000, 8-9
3.0
14.3 14.8
4.0
4.1
12.9 15.5
4.0
Switzerland, 2002-2003, 6-9
Iceland, 2004, 9
17.0
Sweden, 2003, 8
7.0
Cyprus, 1999-2000, 6-9
6.6
United Kingdom: three South Wales localities, 2001-2002, 5
4.6
Ireland, 2001-2002, 4-9
5.8
Italy: five villages in Milan province, 2000-2002, 6-11
5.9
10.3
Portugal, 2002-2003, 7-9
40
16.0 17.0
5.5
Poland, 2000, 1-9
Spain, 1998-2000, 2-9
20.0
3.0
Germany: Zerbst, Hettstedt and Bitterfeld counties, 1998-1999, 5-10
4.4
15.8 14.8
6.3
8.3
13.7 19.5
6.9
16.7 21.7
7.5
18.9 22.5
7.0
10.5
19.1 21.4
20
10
Obese,
measured
13.3 18.0
0
Percentage (%)
Source: WHO Regional Office for Europe, 2006
3.0
11.5 16.6
19.9 21.9
10.3
30
Pre-obese,
measured
12.3
10
20
30
40
Limitations to childhood obesity
surveillance in Europe
 Only around 25% of Member States have
validated national prevalence data on
overweight or obesity in children
 Measurement tools, calculation and
presentation of data are not standardized
 Difficult to monitor time trends, make
international comparisons and evaluate
effectiveness of interventions
Why European childhood obesity
surveillance initiative?
 Key to stimulate adequate political
response and policies
 Routine data provide most robust
information
 Monitor progress of achievement of the
goals set
What will it be?
The childhood obesity surveillance system
will be an ongoing, systematic process
of collection, analysis, interpretation
and dissemination of descriptive
information for monitoring excess body
weight and for use in programme
planning and evaluation.
Country overview
Bosnia &
Herzegovina
UK, Wales
UK, England
Belgium
Bulgaria
Cyprus
Sweden
Spain
The Czech
Republic
Estonia
Slovenia
14
Hungary
Serbia
Ireland
Portugal
Italy
Norway
Latvia
The Netherlands
Malta
Lithuania
New or integration with existing
surveillance systems
 Although each country is free to develop a system that fits
their local circumstances it is imperative that data are
collected according to a common agreed protocol and that
they contain the stipulated core items.
 The system is designed as simple as possible and should not
demand a major investment of public resources.
 There is no intention to replace existing country’s health,
anthropometry and dietary surveillance systems already
ongoing or in the planning, on the contrary, the system
should if possible be integrated with them.
Process
2nd Meeting
Surveillance Initiative
1st Meeting
Surveillance Initiative
Istanbul Conference
1st Data collection
round
Brainstorming
1st MS Consultation
October
2005
October
2006
November
2006
June
2007
September
2007
December
2007
May
2008
Bosnia &
Herzegovina
UK, Wales
UK, England
Belgium
Bulgaria
Process
Cyprus
Sweden
Spain
The Czech
Republic
Slovenia
Estonia
14
Hungary
Serbia
Ireland
Portugal
Italy
Norway
Latvia
The Netherlands
Malta
Lithuania
Data processing
Data analysis
nd data collection
12st Data
collection
round
round
School year
School
year
2009/2010
2007/2008
Spring/Summer
2009/2010
2008
Data
Data reporting
reporting
Prevalence
-Trends
Prevalence
Summer 2008
2010
Autumn
2008
2010
Organization structure
Executive Group
Country Coordination Team
Surveillance Initiative
Investigators Team
---------------------------------------WHO/EURO & PIs each country
Country Coordination Team
Data clerks
Examiners
School
personnel
Advisory Group
Country Coordination Team
Purpose
 The system will be aiming to measure routinely (at
two-year-intervals) the trends in overweight and
obesity in children aged 6.0-9.9 years in order to
•
•
•
have a correct understanding of the progress of the
epidemic in this population in each country
harmonize at the European level and able to make
inter-country comparisons within the WHO European
Region
set the European agenda and report back on trends in
2010 to WHO Regional Committee and EC
Study design
 Semi-longitudinal: each 2 yrs a new crosssectional sample of the same age group will
be drawn.
 Optional: longitudinal
•
•
To estimate incidence and remission rates of
overweight, which enables identification of
target groups for prevention and intervention at
local level.
As children are more likely to become
overweight at earlier ages and are more likely
to remain overweight as they become older.
Setting and Population
 Nationally representative sample of primary
schools / classes
 Sentinel site approach
 Age groups: 6-, 7-, 8 and/or 9-year-olds
 Sample size: final effective sample ≈2800
≈124-140 classes (90%-80% response rate)
Why children aged 6-9-year-olds?
 They precede puberty and eliminate possible
differences between countries that could be
attributed to variations in the age of puberty.
 At these ages the identification is of value to
predict the condition in adulthood.
 Prevention effforst towards children before puberty
will be important in reducing incidence rates and
promoting remission.
 At the age of 6 years the adiposity rebound starts;
•
Onset of 2nd period of rapid growth body fat.
Variables
Examiner’s record form
 Mandatory items
School return form
• measured weight and height
• some school environmental characteristics
 Optional items:
•
•
•
•
•
•
waist and hip circumferences
Family’s record form
dietary intake patterns
physical activity/inactivity patterns
School record form
co-morbidities
family’s socioeconomic characteristics
detailed school environmental characteristics
Implementation
 In close collaboration with teachers,
headmasters and other school personnel
 May be done in context of whole school
approach to promoting health and well-being
 Data collection during 4-8 weeks
•
•
Not during first 2 weeks of a new school term
or immediately after a major holiday
Mornings
Ethical considerations
 Parents will be fully informed about all study
procedures and their informed consent for
the measurements and for data treatment
(written in local language) obtained on a
voluntary basis prior to the child’s enrolment
in the system either through a letter or
through a school information meeting.
 Prior to the measurement also the child is
asked whether s/he agrees with it.
Ethical considerations
 Parents have a right to know their child’s body
height and body weight measures. Although these
will not be given routinely they will be given if
requested.
 Children will never be told the measures of other
children.
 The children’s names will not be included in the
electronic data files.
 It is vital that examiners work in such a way that
stigmatization and bullying are minimized and that
they will acknowledge the children’s and parents’
right to withhold consent.
Data confidentiality
 Confidentiality of all collected and archived data will
be ensured.
 Identification numbers to the children will be
assigned and each register will only mention those
numbers.
 Only one person in the school/project will have a full
list of ID numbers and corresponding names and
addresses of the children sampled.
 No information of the subjects will be given to
outside people.
 Forms will be stored in safe cabinets at the national
coordinating centre.
END PART 1
Thursday 14 February 2008
Schedule
 Part 3
 Review forms and administration guidance
 Instruction in taking the interviewing, recording
answers and checking out forms
 Instruction in taking the anthropometric
measurements and recording the measures
 Instruction in calibrating the instruments
 Instruction in instrument maintenance, storage and
transportation
PART 3
Country coordination team
 Principal investigator (PI); responsible for the
overall coordination and s/he will be a
member of the Surveillance Initiative
Investigators Team.
 Supervisor(s); responsible for the data
collection in each sampled school.
 Data manager; responsible for the overall
data management.
Country team
 Examiners; responsible for the administration
of the examiner’s record form and taking the
anthropometric measurements.
 Data clerks; responsible for the data entry
into electronic data files.
 School personnel responsible for the
completion of the school return forms and
other relevant possible tasks.
Role of examiners
Administration of examiner’s record form.
Takes anthropometric measurements.
Takes care of instruments and its calibration.
Organizes measurement setting in schools.
Gives instructions to teachers where needed.
Assists school director or teacher in completing the
school return form.
 Makes sure that data manager receives the
examiner’s record and school return form.






Role of supervisors
 Tracking examiner’s progress.
 Ensuring data collection forms are completed
correctly.
 Keeping data collection to the specified
timeframe.
 Handling any issues examiners are
encountering.
 First contact with schools.
Data flow chart
mandatory forms
Data collection in primary schools, manual checking of forms
Examiners
Completion of school return forms
School personnel
Forms sent to national coordinating centre where they will be
archived
Data manager national
coordinating centre
Data entry carried out twice
Data clerks
Data cleaning, validation and back-up
Data manager national
coordinating centre
Pooled dataset analysis
Surveillance Initiative
Investigators Team
Standardization of conditions
Examiners
 Prior to each data collection round, all examiners should be
trained and standardized in taking the measurements as
accurately and precisely as possible according to the outlined
measurement techniques and examiners’ instructions.
 Examiners should ensure the basic principles of
confidentiality, privacy and objectivity throughout the process.
 Examiners should not mention the words “childhood obesity”
or give any indication that this data collection refers to the
assessment of the prevalence of overweight and obesity in
school children.
 Examiners should not calculate the child’s BMI values at the
point of measurement.
 Children have a right to know their body height and body
weight measures. Although examiners should not give them
routinely they should be given if requested.
Standardization of conditions
Children
 Children should wear normal, light, indoor clothing
without shoes/socks.
 Prior to the measurements, they should be asked to
take off her/his shoes and socks as well as all
heavy clothing (coats, sweaters, jackets, etc). They
should also be asked to remove wallets, cellular
phones, key chains, belts or any other objects.
Further any hair ornaments or braids should be
undone.
 Children should be asked to go to the toilet just
before the measurements.
 Children should never be told the measurements of
other children.
Standardization of conditions
Instruments
 The same anthropometric measuring
instruments should be used across a country.
 The weighing scale and the stadiometer
should be checked and/or calibrated
frequently, ideally on each of the days that
measurements are taken place and should
then be done early morning beforehand.
 The instruments need to be highly accurate
and precise.
Standardization of conditions
Forms
 All original data collection forms and administration
instructions will be prepared in English and should be
translated to local languages and back-translated to English.
 The translated forms should be carefully checked for
discrepancies with the original English version.
 The re-translation should be carried out independently from
the initial translation from English to the country, preferable
by a professional translator.
 Any of the translated data collection forms and
administration instructions should not give an indication that
this data collection refers to the assessment of the
prevalence of overweight and obesity in school children.
Standardization of conditions
Time
 The anthropometric measurements should
• be carried out over as short a period as possible,
preferable within four weeks and no longer than
eight weeks;
• not take place during the first two weeks of a new
school term or immediately after a major holiday;
• be done in the mornings before lunch time.
Standardization of conditions
Location
 The children should be measured in a private
room.
 The children should not be measured in front
of their class mates.
 Boys and girls will be measured separately.
Support of children with anxieties
 Explain that the objectives of the project: e.g.
The information that will collected will be
used to develop better health programmes for
them.
 Explain how you are going to take the
measurements.
 Take weight measurement first: easiest to
gain co-operation.
 Children should never be forced to take part.
Prevention of stigmatization and
bullying
 Children can be very sensitive about their
own size and those of children around them.
Measuring body height and body weight
could accentuate these sensitivities and
increase the risk of stigmatization and
bullying. Examiners should handle the
process of measuring in such a way as to
minimize any potential for harm
Prevention of stigmatization and
bullying
 Individual results will not be given to any of the
school staff.
 BMI will not be calculated at the point of
measurement.
 Children’s privacy and dignity should be respected
at all times.
 The height and weight displays on the
measurement equipment should not be visible to
anyone apart from the person recording
measurements.
Setting up measurement session in the
schools: prior to the day of measurements
 Contact schools to arrange a convenient time to go
into schools to undertake the measurements.
 Liaise with schools to send out the informed
consent letter to parents.
 Follow up with the schools to check that the letters
have been sent out and followed prior to the day of
the measurements.
 A school information meeting for parents and
teachers involved may be organized.
 A separate note to instruct parents about the clothes
a child should wear on the day of the
measurements.
Setting up measurement session in the
schools: prior to the day of measurements
 With the school’s help, locate a private setting to do
the measurements. In the exceptional case that a
separate room is not available, a screened off area
of the classroom can be used. Other pupils in the
class must not be able to see or overhear the
measurement taking place.
 Contact the school a few days before the day that
you are visiting to confirm that the weighing and
measuring will be taking place and that a separate
room will be available for you to use.
Setting up measurement session in the
schools: on day of measurements
 Obtain from the school a list with all the registered
children of the sampled class, according with their
names, birth dates and residential codes.
 Explain the teacher/school director what is expected
from him/her.
 Provide the school return form and let them
complete it after the measurement session. You
may need to assist them.
 Check the completed form and take it back with
you.
Setting up measurement session in the
schools: on day of measurements
 Ensure the height measure is correctly assembled
and placed on a firm level surface.
 Ensure that weighing scales are placed on a firm
level surface with the read out display concealed
from the participating child and others.
 Explain the measurements to the children plenary.
 Measurement could be part of a physical education
lesson.
 Ask the children to go to the toilet before the
measurements.
Interaction with schools, children and
parents
1.
2.
3.
4.
5.
6.
What should I do if a parent withdraws their child from the
measurement process but the child wishes to participate?
What should I do if a parent is happy for their child to
participate in the surveillance system but the child wishes
to opt out?
What should I do if a child or parent specifically requests
their height and weight data?
Will the results be published by school?
Should children with special needs be weighed and
measured?
Why are postcode or residential code being collected?
Interaction with schools, children and
parents
1. What should I do if a parent withdraws their
child from the measurement process but the
child wishes to participate?
In view of the age of the children involved
surveillance system, you should respect the
parent’s wishes, and sensitively explain to
the child that their parent or carer has asked
for them not to take part.
Interaction with schools, children and
parents
2.
What should I do if a parent is happy for their child
to participate in the surveillance system but the
child wishes to opt out?
Children’s anxieties about being weighed and
measured should be addressed sensitively, and
children should be encouraged to take part.
However, you should respect the child’s wishes
and under no circumstances should an unwilling
child be made to participate.
Interaction with schools, children and
parents
3. What should I do if a child or parent
specifically requests their height and weight
data?
If a parent or child requests the information, the
examiner should provide height and weight
data confidentially to the parent.
Only raw height and weight data should be
provided to parents, and BMI should not be
calculated.
Interaction with schools, children and
parents
4. Will the results be published by school?
No, school league tables will not be published.
Interaction with schools, children and
parents
5. Should children with special needs be
weighed and measured?
Only children who are able to stand on weighing
scales and height measures unaided should
be weighed and measured .
Interaction with schools, children and
parents
6. Why are postcode or residential code being
collected?
Postcode is collected to enable richer analysis of
trends in obesity by allowing analysis by
deprivation. Postcode is not used to identify
individual children, and safeguards will be
placed to protect against this.
END PART 3
MEASUREMENTS
Accuracy
 An examiner is accurate if, on average, he or
she measures real size (with an accurate
instrument).
 He or she is inaccurate (biased) if he or she
has a tendency to record values that are
higher (positively biased) or lower (negatively
biased) than real size.
Accuracy
 Lack of accuracy (bias) can be assessed in a
test-retest study in which several children are
measured by the expert and by the examiner.
 Bias is calculated as the average difference
between the expert and examiner values.
Precision
 An examiner is precise if, when re-measuring
the same child (within an interval during
which the child has not grown and the
instrument not de-calibrated), he or she
records values that tend to be close to each
other and not widely dispersed.
 This is independent of whether their average
is close to real size or not and thus
independent of accuracy.
Precision
 Examiner precision is assessed in a testretest study in which a series of subjects is
measured twice by the examiner, after which
the differences between pairs of
measurements are analysed.
 With perfect precision, the second
measurement will always give the same
value as the first.
Example
Examiner
Measurement
Precision
Accuracy
(estimate of the mean)
1
2
mean
Expert
110
110
110
precise
unbiased
1
108
112
110
imprecise
unbiased
2
108
108
108
precise
negatively biased
3
112
112
112
precise
positively biased