SMS Reminders Fail to Increase Accelerometer Wear Time in Physical Activity Study

Twitter: @heinonmatti
Facebook: Heinon Matti
SMS reminders to
increase accelerometer
wear-time
A within-trial RCT comparing persuasive messages
Reg. no: DRKS00007721
4.5.2016 1

Background
4.5.2016 2

Facebook: Heinon Mattimattiheino.wordpress.com
• Physical activity recommendations based on self-
reported activity levels → problems:
• Remembering past activity
• Reporting “what the researcher wants to hear”
• Solution: objective measurement devices
• New problem: need to wear it for most of the study
period!
‒ E.g. if you only wear the activity device when exercising,
looks like 100% of your day was spent working out!
4.5.2016 3
The ”why”

The ”why”
• Let’s Move It
‒ A school-based multilevel intervention to
increase physical activity and decrease
sitting among youth*
‒ Ongoing since 2012
‒ RCT phase from 2015 to 2017
‒ Ca. 16–19 year-old vocational school
students
‒ Waist-worn accelerometers used
*Hankonen, Heino et al. (in preparation). Randomised controlled
feasibility study of a school-based multi-level intervention to increase
physical activity and decrease sedentary behaviour among older
adolescents.

The Pervasive Problem:
non-wear in accelerometry
• Let’s Move It Feasibility study
• Students fell short of accelerometer wear
targets (>10hrs of data on >4 days)
‒ Qualitative work: non-wear attributed to
forgetting
How do we ensure adequate
accelerometer wear times?

Methods
4.5.2016 6

The setup
• Within-trial RCT during internal pilot study of the
main trial
• Participants wear the accelerometer for seven
consecutive days during Let’s Move It baseline data
collection
• Fight forgetting with (SMS) reminders
• Next question: What kind of reminders?
Could an old
copy machine
help here?

Langer, Blank and Chanowitz (1978)
Mixed success w/ replication: Folkes (1987);
Key, Edlund, Sagarin and Bizer (2009)
”Harnessing the power of
’Because’”…?

Message types: an example
”Reason”, day 3:”Succinct”, day 3:
“Hello! Because the study
wouldn't succeed without
your help, please
remember to put on the
motion measurement device
again and wear it until you
go to sleep (except in the
shower etc.) - thanks!”
[emphasis added]
“Hello! Please remember to
put on the motion
measurement device again
and wear it until you go to
sleep (except in the shower
etc.) - thanks!”

Consenting in Let’s
Move It
accelerometry
N=375
Opting in
SMS n=276
Randomised to
”Reason”
n=138
Randomised to
”Succinct”
n=135
Send failed
n=7
Opting out
n=95
Participants:

• Does providing a reason via SMS influence
accelerometer wear time:
‒ Total wear time
‒ Number of days >10 hours of data accumulated (0-7)
4.5.2016 11
Research questions

• ”Probability of observed (or rarer) data, if null
hypothesis is true”
• (also assumes randomisation, stopping rules etc…)
4.5.2016 12
What’s a ”p-value” again?
When p is high
(eg. p=0.32), no
conclusions can
be drawn!
(Dienes, 2014)
Reactions upon
discovering this
can vary.

• remember, p-value: Probability of data, given H0
• A Bayes factor BF01:
Pr(𝑑𝑎𝑡𝑎 𝑔𝑖𝑣𝑒𝑛 𝐻0)
Pr(𝑑𝑎𝑡𝑎 𝑔𝑖𝑣𝑒𝑛 𝐻1)
4.5.2016 13
A better question?
”Which is more probable, null or alternative?
0 …∞1 31/3
Very roughly:
BF01:
Data favor
alternative
Insufficient data Data favor null
A great explanation: http://alexanderetz.com/2015/11/01/evidence-vs-conclusions/
When
1
10
< BF < 10, evidence quite weak

Results
4.5.2016 14

Total wear time

Facebook: Heinon Mattimattiheino.wordpress.com 4.5.2016 16
Total weartime differences
Bayesian ANOVA
gives us BF01=29.03
1:1 (50%) prior odds
become 1:29,
p(effect)=3%
10:1 (91%) prior odds
become 10:29,
p(effect)=26%

Valid wear day percentages
Χ2(7) = 7.893, p = 0.342
BF01 = 1.27BF01 = 7.09

Measurement days of >10 hours
of valid data
Horizontal lines represent means, with shaded 95% Bayesian Highest Density Intervals (HDIs)

Discussion
4.5.2016 19

Conclusions
• Why didn’t reasons help?
• Hidden moderators blah blah?
• SMS format hinders the effect? (Why?)
• Wearing the device a question of capability, not
motivation?
• No use reasoning with adolescents?
‒ E.g. university students more compliant
• A case of an undead theory?
‒ Ferguson, C. J., & Heene, M. (2012). A Vast Graveyard of Undead Theories.

Conclusions
• Why didn’t reminders help?
• Operationalisation failure?
‒ Messages claimed to have been read but no objective log
data
• Self selection?
‒ Unlikely, as opting in was mostly determined by recruitment
prompt
• Non-wear not due to remembering?
‒ Although they said it was and thought the reminder helped
immensely!

The Lakatos principle:
Meehl, P. E. (1990). Appraising and amending theories: The strategy of Lakatosian
defense and two principles that warrant it. Psychological Inquiry, 1(2), 108–141.
“Accepting the neo-Popperian view that it is inadvisable to persist
in defending a theory against apparent falsifications […] the
rationale for defending by non-ad hoc adjustments lies in the
theory having accumulated credit by strong successes, having lots
of money in the bank.“ – Paul Meehl
- Does the “power of because” lean on Monopoly money?

Thank you!
@heinonmatti
mattiheino.wordpress.com
Questions?
Comments?
Ideas?
https://linkedin.com/in/heinonmatti

SMS Reminders Fail to Increase Accelerometer Wear Time in Physical Activity Study

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