Thisistheauthors’finalpeeredreviewed(postprint)
versionoftheitempublishedas:
Arundell,Lauren,Ridgers,NicolaD.,Veitch,Jenny,Salmon,Jo,Hinkley,TrinaandTimperio,Anna
2013,5‐yearchangesinafterschoolphysicalactivityandsedentarybehavior,Americanjournalof
preventivemedicine,vol.44,no.6,pp.605‐611.
Available from Deakin Research Online: http://hdl.handle.net/10536/DRO/DU:30052793
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Copyright:2013,Elsevier
Five-Year Changes in Afterschool Physical Activity and Sedentary Behavior
Lauren Arundell, BAppSc (Hons), Nicola D. Ridgers, PhD, Jenny Veitch, PhD,
Jo Salmon, PhD, Trina Hinkley, PhD, Anna Timperio, PhD
From the Centre for Physical Activity and Nutrition Research (C-PAN), Deakin University,
Melbourne, Australia
Address correspondence to: Nicola Ridgers, PhD, Centre for Physical Activity and Nutrition
Research, Deakin University, 221 Burwood Hwy, Burwood, 3125, Australia. E-mail:
[email protected].
1
Background: The afterschool period holds promise for the promotion of physical activity,
yet little is known about the importance of this period as children age.
Purpose: To examine changes in 5-6 and 10-12 year-old children’s physical activity and
sedentary time in the after-school period over 3- and 5-years, and to determine the
contribution of this period to daily physical activity and sedentary behavior over time.
Methods: Data from two longitudinal studies conducted in Melbourne, Australia were used.
Accelerometer data were provided for 2053 children at baseline (CLAN: 2001; HEAPS:
2002/3), 756 at 3-year follow-up (T2) and 622 at 5- year follow-up (T3). Light (LPA),
moderate (MPA) and vigorous (VPA) physical activity were determined using age-adjusted
cut-SRLQWV6HGHQWDU\WLPHZDVGHILQHGDV”FRXQWVPLQXWH0XOWLOHYHODQDO\VHV
conducted in April 2012, assessed change in physical activity and sedentary time and the
contributions of the after-school period to overall levels.
Results: Afterschool MPA and VPA decreased among both cohorts, particularly in the
younger cohort who performed less than half of their baseline levels at T3 (MPA: T1=24min
to T3=11min; VPA: T1=12min to T3=4min). LPA also declined in the older cohort. Afterschool sedentary time increased among the younger (T1=42min, T3=64min) and older
cohorts (T1=57min, T3=84min). The contribution of the after-school period to overall MPA
and VPA increased in the older cohort from 23% to 33% over 5 years. In the younger cohort,
the contribution of the after-school period to daily MPA and VPA decreased by 3% over 5
years.
Conclusions: The importance of the afterschool period for children’s physical activity
increases with age, particularly as children enter adolescence.
2
Introduction
The health benefits of physical activity throughout youth are well established1-2 and an
emerging body of evidence suggests that participation in sedentary behaviors may have
independent negative health impacts,3-4 although prospective evidence is not strong.5 Levels
of children’s physical activity and sedentary behavior are, however, suboptimal.6 Identifying
the most promising time periods in which to change children’s health behaviors will assist
future intervention development. The afterschool period is increasingly recognized as an
important and feasible time period in which to promote increases in physical activity and
reductions in sedentary time among children.7-9 After school, children are not restricted by
school schedules and have the opportunity to engage in discretionary active and sedentary
pastimes10, particularly during daylight hours. Inconsistent definitions of the after-school
period (e.g. 4-6pm11, 3.30-8.30pm)12 make direct comparisons between studies difficult;
however, it appears that children are engaging in between 11 minutes of accelerometerdefined moderate-to-vigorous physical activity7 and 77 minutes of pedometer-defined
physical activity13 after school. Moreover, the after-school period can contribute up to 46% of
children’s daily activity levels14 and 52% of their daily steps.15 Boys consistently engage in
more physical activity after school than their female counterparts11,15-17 and it appears that
this time period makes a larger contribution to daily physical activity levels among boys than
among girls.14
The prevalence of after-school sedentary behaviors and the contribution this period makes to
daily sedentary time is difficult to ascertain as studies have used a range of different methods
to assess behavior (e.g. TV log,14 self-report surveys of screen-based sedentary behaviors and
social sedentary behaviors17). Previous studies have used objective measures of after-school
physical activity and sedentary behavior; 12,19-20 however, none have used objective measures
3
to examine changes in the after-school period over time. In the only longitudinal study to
examine changes in after-school behavior over time, Wickel and colleagues found declines in
total activity and increases in sedentary behavior.21 However, their sample was only followed
over a two year period (from age 9-11 years) and used self-report measures.21
Substantial changes may occur from early childhood to late adolescence, particularly as
children transition from elementary to middle school. It is plausible that the importance of the
after-school period to children’s and adolescents’ overall physical activity levels may change
as children age. Identifying the contribution the after-school period makes to overall activity
levels at different stages of childhood is essential for informing the development of
interventions that target periods of the day when young people are potentially most receptive
to behavior change strategies. The aim of this study was to investigate changes in children’s
after-school physical activity and sedentary time over 3- and 5-years and to determine the
contribution of this period to children’s overall physical activity and sedentary time as
children age.
Methods
Data from the Children Living in Active Neighbourhoods Study (CLAN)22 and the Health,
Eating and Play Study (HEAPS)23 were pooled for the current analysis. In brief, CLAN
aimed to examine the influence of the family environment on elementary-school aged
children’s physical activity and sedentary behavior over time22, whilst HEAPS examined the
family influence on children’s eating behaviors and physical activity over 5 years.23 Ethical
approval for both studies was granted by the Deakin University Human Research Ethics
Committee, the Department of Education and Training Victoria and the Victorian Catholic
Education Office. Parents provided informed written consent for their child’s participation at
4
each time point and adolescents also provided informed written consent subsequent to
baseline.
Sample
Elementary schools in metropolitan Melbourne, Australia, with an enrollment greater than
200 students were randomly selected and invited to participate in CLAN and HEAPS. Fortythree schools (18 in low, 7 in middle and 18 in high socio-economic status (SES) areas)
participated. At baseline (T1), all children in Grade Prep (younger cohort, aged 5-6 years)
and Grades 5-6 (older cohort, aged 10-12 years) were invited to participate. Consent was
provided from 2782 children (CLAN: n=1220, 38% response rate; HEAPS: n=1562, 42%
response rate). At baseline, parents in CLAN (T1=2001) and HEAPS (T1=2002/3) were
asked if they would be willing to be contacted about future research. Those willing were
invited to participate in two follow-up measures three- and five- years post baseline (CLAN:
T2=2004, T3=2006; HEAPS: T2=2006, T3=2008).
Measures
Demographic Data
At each time point, parents reported their marital status, highest level of education and
employment status, and that of their partner (if applicable), as well as their child’s sex and
date of birth. Maternal education was used as a proxy of SES and was classified as low (some
high school attendance or less), medium (high school or trade certificate completion) high
(tertiary education), consistent with previous research.24 Across both studies, data were
provided by 2689 parents at baseline, 822 parents at T2 and 695 parents at T3.
5
Physical activity and sedentary time
Physical activity and sedentary time were objectively measured using a uni-axial
accelerometer (ActiGraph 7164 model, Florida, USA). Accelerometers have been validated
for assessing children’s physical activity and sedentary time in laboratory and field settings.—
25-26
The unit was worn on the right hip for up to eight consecutive days and measured
movement in 1-minute epochs. Children were instructed to wear the monitor during all
waking hours, excluding water-based activities. For the current study, the after-school period
was defined as the end of the school day as determined by the school bell times (usually
3.30pm) until 6pm on weekdays. This is consistent with a previous longitudinal examination
of children’s physical activity during the after-school period.21
Accelerometry data management
Accelerometer data were downloaded and initially checked for compliance using ActiLife
software. Data were then analyzed using specifically developed Excel macros. Non-wear
WLPHZDVGHILQHGDV•FRQVHFXWLYHPLQXWHVRI]HURFRXQWV, which has been commonly used
to define non-wear in children and adolescents.27 Children who provided valid after-school
and whole day data on at least three weekdays were included in analyses. A valid weekday
ZDVGHILQHGDVDGD\RQZKLFKWKHPRQLWRUZDVZRUQIRU•PLQXWHV 7•PLQXWHV
7RU•PLQXWHV77KLVUHSUHVHQWVQRQ-missing counts for at least 80% of a standard
measurement day which is defined as the length of time that at least 70% of the sample wore
the monitor.28 In addition, children were required to have worn the monitor for 50% of the
after-school period.29 At baseline, 2053 children were included in the analyses. At T2 and T3,
756 children (87.1% of sample monitored) and 622 children (87.7% of sample monitored),
respectively, met the inclusion criteria.
6
Data were analyzed using age-specific cut-points30 to determine time spent in light physical
activity (LPA: 1.5-3.99 METs), moderate physical activity (MPA: 4-5.99 METs) and
vigorous physical activLW\93$•0(7VA 4-MET threshold was used to represent MPA
as brisk walking, which is often used to identify MPA in calibration studies, and has been
associated with this level of energy expenditure.31 6HGHQWDU\WLPH6('ZDVGHILQHGDV”
counts per minute.32 The average time spent in SED, LPA, MPA and VPA was computed for
each valid day and each valid after-school period. The contribution of the after-school period
was computed as a percentage for each valid day (duration of each activity intensity in the
after-school period /total duration of the activity intensity for that day × 100) and averaged
across valid days.
Statistical Analyses
Data were analyzed in April 2012. Descriptive statistics were calculated for all measured
variables. Independent t-tests revealed significant differences between boy’s and girl’s
physical activity levels in the after-school period and for the whole week day. All subsequent
statistical analyses were stratified by sex. In addition, at each time point children who
provided five days of data engaged in more SED and LPA and less MPA and VPA compared
to children with three or four days of data. Therefore, analyses were adjusted for number of
valid days.
Multilevel analyses (MLwiN 1.10 software, Institute of Education, University of London,
UK) were used to examine changes in children’s physical activity levels and sedentary time
during the after-school period and the contribution of the after-school period to daily physical
activity and sedentary time. As multilevel models are robust regarding missing data points
and can estimate effects over time using incomplete data sets,33 all valid data points collected
7
were used in the analyses. A three-level multilevel model was used. Level 1: measurement
time point (T1, T2, T3); Level 2: children; and Level 3: baseline school. The percentage of
time spent in SED, LPA, MPA and VPA after school, and the contribution of the after-school
period to daily SED, LPA, MPA and VPA were the outcome variables. SES (maternal
education), maternal employment, study (i.e. CLAN or HEAPS), number of valid days,
season of measurement and daily wear time were identified as potential confounding
variables a priori and included in the final analyses. Analyses were also stratified by age
cohort. To examine changes in the outcome variables, two dummy variables were generated.
These were for physical activity levels at T2 (3-year change) and T3 (5-year change)
compared to T1. The random structure considered random intercepts and random slopes on
T2 and T3. Separate analyses were conducted for the outcome variables. The regression
coefficients were assessed for statistical significance using the Wald Statistic,34 which was set
at p < 0.05.
Results
At baseline, 33% of participants had low, 35% medium and 32% high levels of maternal
education. The percent of the after-school period and of the whole day children spent in
physical activity and sedentary time (by sex and cohort) at baseline is shown in Table 1.
Among both the younger and older cohorts, boys engaged in significantly less LPA and
significantly more MPA and VPA than girls during the after-school period. Appendix A
illustrates the three- and five- year changes in the younger and older cohorts’ after-school
behaviors using raw scores. After-school SED time increased from 42 min at T1 to 64 min at
T3 for the younger cohort and from 57 minutes at T1 to 84 minutes at T3 for the older cohort.
Both cohorts decreased their MPA (younger cohort T1=24 min to T3=11 min; older cohort
T1=13 min to T3=9 min) and VPA (younger cohort T1=12 min to T3=4 min; older cohort
8
T1=6 min to T3=2 min) while declines were observed for LPA among the older cohort only
(T1=76 min to T3=65 min).
INSERT TABLE 1
Table 2 shows percentage changes in after-school PA and SED over three and five years
according to sex using multilevel analyses. Significant decreases were observed for MPA and
VPA for boys and girls in both cohorts; however, the magnitude of change was greater
among the younger cohort. Among the older cohort there were large significant decreases in
LPA over three and five years with greater declines observed among the girls. In both cohorts
children’s after-school sedentary time significantly increased over 3- and 5-years in boys and
girls. The change in the proportion of time that both cohorts engaged in physical activity after
school using raw scores is presented in Appendix A (available online at
www.ajpmonline.org).
INSERT TABLE 2 & 3 ABOUT HERE
Among both cohorts the contribution of the after-school period to daily LPA and SED
remained relatively stable at approximately 17% and 20% respectively for the younger cohort
and 16% and 21% respectively for the older cohort. The greatest changes were seen in the
contribution to daily MPA and VPA, with the period making a greater contribution to daily
levels over time in the older cohort (23% at baseline and 33% at T3 for both MPA and VPA).
Changes in the contribution of the after-school period to daily physical activity and sedentary
time over 3- and 5-years according to sex using multilevel analyses are shown in Table 3.
Overall, there were few consistent changes in the contribution the after-school period made to
9
the younger boys’ and girls’ daily PA or SED. In the older cohort, the contribution of the
after-school period to each intensity of physical activity and sedentary time increased over 3and 5-years, with the exception of boys’ sedentary time (significant at 3-years only) and LPA
(significant at 5-years only). The relative contribution of the after-school period to daily
physical activity using raw scores is presented in Appendix B (available online at
www.ajpmonline.org).
Discussion
Consistent with previous research, both MPA and VPA declined during the after-school
period in both cohorts.21,35 However, larger decreases were observed in LPA in the older
cohort compared to MPA and VPA. These data indicate that all physical activity intensities
decreased over time. Further research is needed to identify what behaviors youth engage in
that correspond to these intensities to inform future intervention efforts36. Interestingly, the
contribution of the after-school period to daily MPA and VPA was greater for the older
cohort over time (from under one-quarter of the daily physical activity levels to over onethird) compared to the younger cohort (stable at ~25%), highlighting the increasing
importance of this time period to young people’s overall daily physical activity levels.
The relative decline in MPA and VPA was greater among younger children compared to the
older children. Although age-related physical activity declines are consistently observed
when examining daily behavior,37 amongst the after-school literature there are mixed
findings. Declines in physical activity have been found in European samples,35 whereas
among British youth (n=1307, aged 10-12 years)38 after-school physical activity increased
with age. Few studies have examined the after-school behaviors of children during the early
elementary school years with the main focus being on the behaviors of older children and
10
adolescents.18,39-40 This study suggests that children’s after-school behaviors undergo major
changes between the age of 5/6 and 10/11 years, which may be explained in part by increases
in screen-time usage such as TV viewing and electronic media.41 Further, it highlights the
need for interventions to target children’s after-school MPA and VPA from early elementary
school as although declines in after-school activity levels are seen, it is a period where
children may be able to participate in greater amounts of discretionary physical activity
compared to other periods throughout the day.
At baseline the older cohort in this Australian sample spent a similar proportion of the afterschool period engaged in MPA and VPA compared with the accelerometer measured MVPA
levels of 9-year olds in the European Youth Heart Study.35 Notably, there were large declines
seen in after-school LPA among the older cohort, particularly for girls. Interestingly, the
greatest increase in the contribution the after-school period makes to daily activity levels was
observed in the first three years among the boys (i.e. during their transition from elementary
school to secondary school); whereas among the girls, there were consistent increases in the
contribution over three- and five-years. Previous research has found that as youth progress
through secondary school they perform less physical activity throughout other periods of the
day (e.g. recess and lunchtime),29 possibly suggesting that the in-school time contribution to
physical activity levels decreases over time. This highlights the importance of the afterschool period for youth to engage in physical activity and to promote activity levels through
interventions during this time. After-school programs hold promise as one setting for
increasing physical activity levels in youth,42-43,41 though further research is needed to
identify which specific strategies are most effective in these settings over time.44
11
Boys and girls in both cohorts showed increases in after-school sedentary time of a similar
magnitude (approximately 25 minutes) over 3- and 5-years. Increases in the contribution to
daily sedentary levels were minimal suggesting this increase is consistent across the entire
day. The observed increase may in part be due to school timetabling and homework
expectations as 54% of children (5-12 years) have previously reported homework to be a
barrier to participation in physical activity after school.45 However, Atkin and colleagues
found that among 15 year old students in the Project STIL (Sedentary Teenagers and Inactive
Lifestyles), physical activity did not displace time spent doing homework between 3.306.30pm, suggesting that other factors (e.g. TV viewing) may contribute to these changes.18
The after-school period may be a key time to target reductions in children’s and adolescents’
sedentary time as it may be more challenging to change children’s sedentary time during
structured school time, particularly as children progress through secondary school, or later in
the evenings (after 6pm). One promising approach may be the modification of homework
tasks that target both physical activity engagement and sedentary time during this time,4647
though further research is needed to identify the effectiveness of such strategies in children
and adolescents.
Strengths of this study include the large sample size, the use of objective measures of
sedentary time and physical activity, and the five-year follow-up period. Limitations include
the use of a 60-second epoch for the accelerometry, as this may not be sensitive enough to
capture sporadic VPA among children.48 However, this epoch length was unavoidable when
using the 7164 accelerometer model over extended periods of time. Second, defining nonwear as 20 minutes of consecutive zeros may be considered to be a limitation, as this may
have resulted in an underestimation of sedentary time27. Third, as accelerometers do not
12
capture behavioral information, it is not known what types of behaviors changed during the
after-school period as children aged.
Conclusion
This study suggests that the after-school period may be an important time period for
interventions targeting physical activity and sedentary time throughout childhood and
adolescence. Children and adolescents’ after-school physical activity declines over time with
changes in both MPA and VPA occurring during elementary school years and changes in
LPA occurring during secondary school. Large increases in sedentary time were also
observed, particularly over the 5-year period. The increasing contribution that the afterschool period makes to overall physical activity, particularly during adolescence, suggests
that after-school initiatives may be particularly important in this age group. However,
interventions targeting both physical activity and sedentary behavior should begin during the
early elementary school years to minimize the changes observed in the younger years.
13
Acknowledgements
The authors gratefully acknowledge the contribution of all project staff, especially Dr
Michelle Jackson, Dr Amanda Telford, Sophie Thal-Janssen and Anna Stzendur for the
collection of data in both studies, and Eoin O’Connell for the analysis of the raw data. Data
collection for HEAPS was funded by the Victorian Health Promotion Foundation (baseline)
and Australian Research Council (follow-ups; ID DP 0664206) and for CLAN by the
Financial Markets Foundation for Children (baseline) and the National Health and Medical
Research Council (follow-ups; ID 274309). Nicola Ridgers is supported by an Australian
Research Council Discovery Early Career Researcher Award (DE120101173). Jenny Veitch
is supported by a National Heart Foundation of Australia Postdoctoral Fellowship Award. Jo
Salmon is supported National Health & Medical Research Council Principal Research
Fellowship (APP1026216). Anna Timperio is supported by a Victorian Health Promotion
Foundation Public Health Fellowship.
No financial disclosures were reported by the authors of this paper.
14
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19
Table 1: Children’s physical activity and sedentary time at baseline (T1)
Younger Cohort¥
Older Cohort‡
Girls (n=295)
Boys (n=313)
Girls (n=789)
Boys (n=656)
Mean (SD)
Mean (SD)
Mean (SD)
Mean (SD)
After school (150 minute period)
%SED
27.87 (9.26)
27.80 (9.67)
37.93 (10.67)
37.60 (11.73)
%LPA
49.40 (7.86)*
47.20 (8.40)*
52.07 (9.13)*
48.67 (9.47)*
%MPA
15.73 (5.20)*
16.73 (5.53)*
7.60 (3.93)*
9.67 (5.13)*
%VPA
6.80 (4.53)*
8.80 (5.60)*
3.06 (3.26)*
4.53 (4.40)*
%SED
33.63 (9.3)
31.96 (9.04)
44.91 (10.57)*
42.70 (10.49)*
%LPA
48.15 (6.05)
46.90 (5.94)
46.74 (7.06)
46.19 (6.99)
%MPA
13.04 (2.97)
14.12 (2.93)
6.03 (2.04)
7.60 (2.17)
%VPA
5.18 (2.17)*
7.00 (2.96)*
2.33 (1.58)*
3.51 (2.14)*
750.6 (±70.5) *
755.6 (±66.7)*
807.8 (±80.6)*
814.0 (±81.6)*
Daily activity
Daily wear time
(mins)
¥
5-6 years old at baseline; ‡ 10-12 years old at baseline; *p<0.05.
SED = Sedentary time (<100 counts per minute),31 LPA = Light intensity physical activity;
MPA = Moderate intensity physical activity; VPA = Vigorous intensity physical activity
using age adjusted thresholds.29
20
-0.31 (-2.02 to 1.40)
-5.14 (-6.22 to -4.06)***
-2.85 (-3.98 to -1.69)***
%LPA
%MPA
%VPA
1.09 (-0.77 to 2.95)
-5.16 (-6.15 to -4.17)***
-1.96 (-2.74 to -1.17)***
%LPA
%MPA
%VPA
-4.37 (-5.24 to -3.50)***
-8.30 (-9.29 to -7.30)***
-2.01 (-4.03 to 0.02)
14.54 (12.18 to 16.90)***
-5.41 (-6.55 to -4.27)***
-7.99 (-9.09 to -6.89)***
0.09 (-1.65 to 1.83)
13.37 (11.30 to 15.44)***
7WR7ȕ&,
-1.16 (-1.58 to -0.73)***
-1.06 (-1.82 to -0.30)**
-8.44 (-9.98 to -6.91)***
10.73 (9.04 to 12.42)***
-0.90 (-1.58 to -0.22)**
-1.98 (-2.83 to -1.14)***
-6.35 (-7.92 to -4.78)***
9.34 (6.57 to 12.12)***
7WR7ȕ&,
-1.99 (-2.47 to -1.52)***
-2.03 (2.93 to -1.13)***
-11.55 (-13.12 to -9.99)***
15.61 (13.98 to 17.24)***
-2.47 (-3.21 to -1.74)***
-3.62 (-4.53 to -2.71)***
-9.18 (-10.97 to -7.39)***
15.40 (12.88 to 17.92)***
7WR7ȕ&,
Older Cohort‡
years at T2, 15-17 years at T3.
21
***p < 0.001, **p < 0.01, *p<0.05. CI = Confidence intervals. ¥ 5-6 years at T1, 8-9 years at T2, 10-11 years oat T3; ‡ 10-12 years at T1, 13-15
5.36 (3.37 to 7.34)***
%SED
Girls
8.37 (6.32 to 10.41)***
%SED
Boys
7WR7ȕ&,
Younger Cohort¥
Table 2: Mean changes in percentage of time spent in physical activity and sedentary time after school over 3- and 5-years.
measurement, maternal education, maternal employment, number of valid days, and daily wear time.
7ZKLOVWDQHJDWLYHȕYDOXHUHIOHFWVDGHFUHDVHLQVHGHQWDU\WLPHDQGSK\VLFDODFWLYLW\$OOPRGHOVDUHDGMXVWHGIRUVWXG\ season of
22
<HDU7$SRVLWLYHȕYDOXHUHIOHFWVDQLQFUHDVHLQFKLOGUHQ¶VVHGHQWDU\WLPHDQGSK\VLFDODFWLYLW\DIWHUVFKRRl at either T2 or T3 compared to
TKHȕYDOXHUHIOHFWVWKHSHUFHQtage change in children’s after-school activity levels between Year 1 (T1) and Year 3 (T2) and Year 1 (T1) and
0.36 (-0.37 to 1.09)
0.57 (-0.89 to 2.04)
0.67 (-2.08 to 3.42)
%LPA
%MPA
%VPA
0.97 (0.40 to 1.53)***
2.04 (0.48 to 3.59)*
3.26 (0.37 to 6.15)*
%LPA
%MPA
%VPA
-1.79 (-4.99 to 1.41)
0.42 (-1.30 to 2.15)
0.78 (0.15 to 1.41)*
0.68 (-0.19 to 1.55)
0.12 (-3.71 to 3.95)
-1.93 (-3.42 to -0.43)*
0.28 (-0.43 to 0.98)
1.23 (0.23 to 2.22)**
7WR7ȕ&,
8.25 (5.15 to 11.35)***
6.51 (4.77 to 8.24)***
1.36 (0.86 to 1.85)***
1.58 (1.07 to 2.08)***
10.42 (7.14to 13.67)***
4.79 (2.89 to 6.69)***
0.45 (-0.16 to 1.05)
0.80 (0.12 to 1.48)*
7WR7ȕ&,
7.49 (4.02 to 10.96)***
12.61 (10.68 to 14.54)***
3.01 (2.45 to 3.56)***
0.91 (0.35 to 1.48)**
11.15 (7.64 to 14.66)***
5.97 (3.92 to 8.01)***
2.36 (1.70 to 3.00)***
0.68 (-0.05 to 1.42)
7WR7ȕ&,
Older Cohort‡
23
***p < 0.001, **p < 0.01, *p<0.05 ¥ 5-6 years at T1, 8-9 years at T2, 10-11 years at T3; ‡ 10-12 years at T1, 13-15 years at T2, 15-17 years at T3.
Models adjusted for study, season of measurement, maternal education, maternal employment, number of valid days, and daily wear time.
-0.80 (-1.58 to -0.02)*
%SED
Girls
0.79 (-0.17 to 1.77)
%SED
Boys
7WR7ȕ&,
Younger Cohort¥
Table 3: Mean change in the contribution of the after-school period to daily physical activity and sedentary time
levels between Year 1 (T1) and Year 3 (T2) and Year 1 (T1) and Year 5 (T3). CI = Confidence intervals.
24
7KHȕYDOXHUHIOHFWVWKHSHUFHQWDJHFKDQJHLn the contribution of the after-school period to children’s daily sedentary time and physical activity