- Email: [email protected]
Point-of-Choice Prompts to Reduce Sitting Time at Work
Point-of-Choice Prompts to Reduce Sitting Time at Work A Randomized Trial Rhian E. Evans, MSc, Henrietta O. Fawole, MSc, Stephanie A. Sheriff, MSc, Philippa M. Dall, PhD, P. Margaret Grant, PhD, Cormac G. Ryan, PhD Background: Prolonged sitting is prevalent in the workplace and is associated with adverse health markers.
Purpose: Investigate the effects of point-of-choice (PoC) prompting software, on the computer used at work (PC), to reduce long uninterrupted sedentary periods and total sedentary time at work. Design: Assessor-blinded, parallel group, active-controlled randomized trial. Setting/participants: A convenience sample of offıce workers from Glasgow, United Kingdom. Data were collected April to June 2010, and analyzed October 2010 to June 2011. Intervention: The education group (n⫽14) received a brief education session on the importance of reducing long sitting periods at work. The PoC group (n⫽14) received the same education along with prompting software on their PC for 5 workdays, which reminded them to stand up every 30 minutes.
Main outcome measures: Sitting time was measured objectively using the activPAL™ activity monitor for 5 workdays at baseline and 5 workdays during the intervention. The number and time spent sitting in events ⬎30 minutes’ duration were the main outcome measures.
Results: At baseline, participants spent 5.7⫾1.0 hours/day (76%⫾9%) of their time at work sitting. Of that time, 3.3⫾1.3 hours/day was spent sitting in 3.7⫾1.4 events ⬎30 minutes. There was a signifıcant difference between the groups in the change (intervention to baseline) of both the number (ANCOVA; ⫺6.8%, p⫽0.014) and duration (⫺15.5%, p⫽0.007) of sitting events ⬎30 minutes. During the intervention, compared with baseline, the PoC group reduced the number (paired t-test; ⫺0.11 events/hour, p⫽0.045) and duration (⫺12.2%, p⫽0.035) of sitting events ⬎30 minutes. However, there was no signifıcant difference in total sitting time between groups (⫺4.4%, p⫽0.084). Conclusions: Point-of-choice prompting software on work computers recommending taking a break from sitting plus education is superior to education alone in reducing long uninterrupted sedentary periods at work. Trial registration: This trial was registered at ClinicalTrials.gov NCT01628861. (Am J Prev Med 2012;43(3):293–297) © 2012 American Journal of Preventive Medicine
edentary behavior, time spent sitting/supine,1–5 is a risk factor for morbidity and mortality, independent of physical activity.2,6 –10 In addition, long uninterrupted sedentary events are independently associated with adverse health markers.11,12 Employees sit at work for
⬃77% of the time,13 mostly (51%) accumulated in periods longer than 30 minutes.14 Workplace interventions aiming to reduce sedentary behavior have not been reported, whereas those aimed at increasing physical activity do not decrease self-reported sitting time.15 The current study tested whether using prompting software on a personal computer (PC) used at work, in addition to education, re-
From the School of Health and Life Sciences (Evans, Fawole, Sheriff, Dall, Grant), Glasgow Caledonian University, Glasgow; and the School of Health and Social Care (Ryan), Teesside University, Middlesbrough, United Kingdom Address correspondence to: Philippa M. Dall, PhD, Research Fellow,
School of Health and Life Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, United Kingdom, G4 0BA. E-mail: philippa. [email protected]. 0749-3797/$36.00 http://dx.doi.org/10.1016/j.amepre.2012.05.010
Introduction
S
© 2012 American Journal of Preventive Medicine • Published by Elsevier Inc.
Am J Prev Med 2012;43(3):293–297 293
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duced long uninterrupted sedentary periods and total sedentary time at work compared to education alone.
Methods Design This assessor-blind, parallel group, active-controlled randomized trial compared two groups of offıce workers. The education-only group received an education session on the adverse health effects of sitting for long periods. The point-of-choice (PoC) group received the same education along with prompting software on their PC reminding them to stand every 30 minutes.
Participants A convenience sample of 30 healthy working adults was recruited via poster and e-mail in April–May 2010. All participants worked in an offıce at Glasgow Caledonian University, United Kingdom (UK), and could stand unassisted. There was no racial or gender bias in the selection of participants. Demographic information (age, gender, height, weight, occupational role, smoking status) was recorded. Ethical approval was obtained from Glasgow Caledonian University. Written informed consent was provided.
Baseline Measurement Period Participants wore the activPAL™ (PAL technologies, UK) at work for 5 workdays. The thigh-mounted activPAL provides timestamped acceleration, classifıed into sitting/lying, standing, and walking. The monitor is valid for adults16 –18 and has greater sensitivity to change than other monitors.18 Participants recorded time of arrival (monitor application) and departure (monitor removal) from work in a diary. An e-mail reminding participants to wear the monitor was sent at the start of each workday.
Education Immediately after the baseline measurement period, each participant individually received a short educational talk, read from a script, regarding the health risks of prolonged sitting, stating that standing every 30 minutes could be benefıcial, and a short information leaflet was provided (Appendix A, available online at www.ajpmonline.org).
Group Assignment Random number generation was used to place group assignment into sequentially numbered sealed opaque envelopes by a researcher not delivering the intervention. The next numbered envelope was opened by the researcher, immediately after the education session. Participants were either assigned to the education group (education only) or the PoC group (PoC plus education), and the participant was aware to which group they were allocated.
Prompting Software Participants in the PoC group then additionally had prompting software (MyRestBreak 1.0, ©Vikram Sharma, www.my-restbreak.software.informer.com) loaded onto their PC, which was used during the 5-workday intervention period. An advice window (11X9 cm), reminding participants to take a break, appeared on the monitor, for 1 minute every 30 minutes from the time the PC was
started. The window could not be minimized or moved, but participants could work in any opened windows around it.
Intervention Measurement Period The 5-workday intervention measurement period started immediately, concurrent with the intervention, following the same procedure as for the baseline measurement period.
Data Treatment Data treatment was conducted by a researcher blinded to the allocation of the participant. Data were classifıed into sitting, standing, and walking by proprietary software (version 5.9.1.1, PAL technologies, UK); subsequent data processing was performed by custom software (visual basic for applications in Excel). Reported diary information was used to determine the start/end of each workday. Sedentary periods crossing the reported start/end of the workday were included if most of the sedentary period was within stated work hours and no more than 10 minutes was outside. The minimum data requirement for inclusion was 2 workdays, of at least 4 hours’ duration, in each of the measurement periods. Total time sitting and the number of sitting events (equivalent to the number of breaks in sitting) were used as outcome measures to represent overall sedentary behavior at work. A prolonged sitting event was defıned as ⱖ30 minutes, fıtting the timescale of the intervention. The number of prolonged sitting events and the duration of prolonged sitting events were used to represent prolonged sedentary behavior. Outcome measures were standardized by dividing them by the duration of the workday.
Statistical Analysis Statistical analyses were performed on the standardized outcome measures using SPSS (PASW 18.0). Demographic information and baseline outcome measures were compared between the two groups, using independent samples t-test (normal continuous data, assessed by Kolgorov–Smirnov test) and chi-square test (categoric data). Changes in outcome measure (intervention– baseline) were assessed using paired t-tests, whereas the difference in change in outcome (intervention– baseline) between the two groups was compared using ANCOVA, with the respective baseline as covariate. Between-group standardized effects size and post hoc sample size were calculated.
Results Thirty participants were recruited (Figure 1). Of 278 workdays monitored, 11 were excluded from analysis because of a short reported workday (n⫽3); technical diffıculties (n⫽3); or nonwear (n⫽5). Two participants were excluded because of insuffıcient data. The median number of workdays analyzed was 5 (21 participants) at baseline and 5 (18 participants) during the intervention. Measurement periods ⬍4 days were 2 workdays (two participants, baseline) and 3 workdays (one participant baseline, one participant intervention). The inclusion/exclusion of sitting events crossing the reported start/end of the workday resulted in a net reduction of 77.8 hours (3.9%). The mean (⫾SD) duration of a workday was 7.5⫾0.8 hours/day (median 7.6 hours/day; range 4.0 –12.1 hours/ www.ajpmonline.org
Analysis
Allocation
Enrollment
Evans et al / Am J Prev Med 2012;43(3):293–297
295
Baseline Sedentary Behavior
30 volunteered 30 randomized
15 allocated to PoC prompt and education group
15 allocated to education-only group
1 lost to data analysis due to insufficient data
1 lost to data analysis due to insufficient data
14 analyzed
14 analyzed
Figure 1. CONSORT flow diagram
At baseline, participants spent (M⫾SD [range]) 5.7⫾1.0 hours/day (76%⫾9% [2.4 –9.8 hours/day, 46%–96%]) at work sitting, in 26⫾10 events (3.4⫾1.2 events/hour [7– 67, 0.9 –18.3 events/hour]). Participants had 3.7⫾1.4 (0.49⫾0.18 events/hour [0 – 8, 0.00 –1.21 events/hour]) prolonged sitting events, which lasted 3.3⫾1.3 hours/day (55%⫾20% [0.0 –7.2 hours/day, 0%–97%]). There were no statistical differences between groups at baseline.
Effect of the Intervention on Sedentary Behavior
PoC, point-of-choice
day). Participants had normal BMI (23.7⫾3.5 vs 23.6⫾2.8, PoC/Ed group); were predominantly female (n⫽11/11); and worked as administrators (n⫽4/3), researchers (n⫽5/7), or lecturers (n⫽5/4); all were nonsmokers. The PoC group (aged 49⫾8 years) was older than the education group (aged 39⫾10 years; p⫽0.008).
The only within-group differences were for the number (⫺0.11 events/hour) and duration (⫺12.2%) of prolonged sitting events (Table 1). There was no betweengroup difference (estimated marginal mean difference PoC– education [95% CI], p-value) in total sitting time (⫺4.4% [⫺9.6%, 0.6%], p⫽0.084). There were signifıcant between-group differences in the total number of sitting
Table 1. Sedentary behavior of participants
Total sitting time (hours/day [%])
Group
BL
Int
Change (Int-BL)
Difference (PoC-Ed)
PoC⫹Ed
5.9⫾1.0
5.6⫾1.1
⫺0.3⫾0.9
⫺0.3⫾0.3
(78.1⫾6.9)
(75.0⫾9.9)
(⫺3.1⫾7.0)
(⫺4.4⫾2.4)
5.6⫾1.0
5.7⫾0.9
0.1⫾0.6
(74.0⫾11.0)
(76.4⫾8.0)
(2.4⫾6.6)
26⫾11
28⫾9
1.6⫾5.3ⴱ
4.3⫾1.9
(0.3⫾0.5)
(0.5⫾0.2)
Ed-only
Number of sitting events (events/ day [events/hour])
PoC⫹Ed
(3.4⫾1.1) Ed-only
Number of prolonged sitting events (events/day [events/hour])
PoC⫹Ed
Ed-only
Duration of prolonged sitting events (hours/day [%])
PoC⫹Ed
Ed-only
(3.7⫾1.0)
ⴱ
23⫾10
⫺2.4⫾5.7
(3.3⫾1.3)
(3.1⫾1.4)
(⫺0.3⫾0.7)
3.5⫾1.4
2.7⫾1.3
⫺0.8⫾1.6ⴱ
(0.47⫾0.19)
(0.36⫾0.19)
(⫺0.11⫾ 0.19)
25⫾9
⫺1.1⫾0.4ⴱⴱ (⫺0.14⫾0.05)
ⴱ
3.8⫾1.4
3.9⫾1.2
0.1⫾0.9
(0.50⫾0.48)
(0.52⫾0.15)
(0.02⫾0.12)
3.1⫾1.2
2.3⫾1.4
⫺0.8⫾1.4ⴱ
(51.9⫾19.3)
(39.7⫾21.2)
(⫺12.2⫾ 19.3)
⫺1.0⫾0.4ⴱⴱ (⫺15.4⫾5.3)
ⴱ
3.5⫾1.5
3.6⫾1.3
0.1⫾0.7
(58.5⫾20.5)
(59.7⫾17.4)
(1.2⫾7.9)
Note: Data shown in each cell are M⫾SD for both the actual value of the outcome measure per day and for the standardized outcome measure (shown in parentheses). All statistics were performed on standardized data. Outcome measures of time spent sitting have units of hours/day (% of workday); outcome measures of events have units of events/day (events per hour at work). Prolonged sitting was defined as sitting continuously for ⬎30 minutes. The PoC⫹Ed group received a computer prompt to stand every 30 minutes plus verbal and pamphlet education. The Ed group received verbal and pamphlet education. Bold indicates significance. *Difference in outcome measure significantly different between the groups (p⬍0.05) **Outcome measure significantly different at intervention compared to baseline (p⬍0.05) BL, baseline measurement period; Change (Int-BL), within-group change in outcome at the intervention measurement period compared to baseline; Ed, education; Difference (PoC-Ed), between-group difference in outcome measure of the change (intervention– baseline); Int, intervention measurement period; PoC, point-of-choice
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events (0.54 events/hour [0.07, 1.02], p⫽0.027) and for the number (⫺0.14 events/hour [⫺0.25, ⫺0.03], p⫽0.012) and duration (⫺15.4% [⫺26.2%, ⫺4.5%], p⫽0.007) of prolonged sitting events. Standardized effect sizes between groups of the change in outcome (intervention– baseline) were small (number of sitting events, 0.44) or moderate (total sitting time, 0.60; number of prolonged sitting events, 0.69; total time sitting in prolonged events, 0.68). Post hoc calculations indicated that 44 individuals per group would be required to show a signifıcant (80% power, p⫽0.05) difference between groups in total sitting time.
Discussion Measured objectively, there was no difference on total time spent sitting. However, both the number of and the time spent sitting in prolonged sitting periods (⬎30 minutes’ duration) were reduced in the PoC-plus-education group and differed in comparison to the lack of change in the education-only group. To our knowledge, this is the fırst RCT to investigate the effects of an intervention specifıcally targeted to reduce adverse sedentary behavior in the workplace. One workplace intervention aiming to increase physical activity through incidental activity demonstrated a nonsignifıcant self-reported reduction in sitting at work of 15 minutes,19 a similar absolute level to the present study (17 minutes). Three nonworkplace interventions aimed at reducing sedentary behavior demonstrated pre–post reductions in objectively measured sitting from 3.2% to 4.3%.18,20,21 These reductions are of a similar magnitude to that of the PoC group in the current study (⫺3.1%), despite the studies using different activity monitors (activPAL18; actigraph20; SenseWear armband21) and interventions (behavioral18,20; TV-lockout21), in different populations (older adults20; overweight/obese adults18,21). Only one of these studies included a control group.21 The PC prompt used in the present study was related to the time the PC was switched on in the morning, and not necessarily to the sitting behavior of the participant. Despite this, prolonged sitting was reduced in the PoC group compared to the education-only group, although whether participants were responding specifıcally to the prompts, or using them as general reinforcement to the education is unclear.
Limitations and Strengths A limitation of the present study is its small sample size. The PoC group was signifıcantly older than the education group. Adults tend to become more sedentary as they get older22; however, the potential effect of age on compliance with the intervention is unclear. There are no
evidence-based guidelines on the appropriate maximum period of sitting duration for health. The recommendation to stand every 30 minutes was selected from the range of informal recommendations that exist (20 minutes,23 30 minutes,24 55 minutes3). There is no evidence that altering sedentary patterns to fıt this recommendation will have health benefıts. The duration of the intervention was short (3–5 workdays) and there was no long-term follow-up. There was no process evaluation to ascertain if the intervention was delivered as intended or whether participants found the intervention useful. Strengths of this paper were the novel intervention paradigm, the assessment of patterns of sedentary behavior,5,14 and the use of an objective measurement of sedentary behavior.16,19,22,25
Conclusion A health promotion intervention specifıcally targeting sedentary behavior at work—point-of-choice prompts on work computers reminding individuals to take a 1-minute break from sitting every 30 minutes—reduced the number of, and time spent in, prolonged (⬎30 minutes) uninterrupted sitting periods compared to education alone. This study was funded by the School of Health, Glasgow Caledonian University, and formed the dissertation project for Masters of Rehabilitation Science of Rhian Evans, Henrietta Fawole, and Stephanie Sheriff. No fınancial support was received from any commercial company. No fınancial disclosures were reported by the authors of this paper.
References 1. Biddle SJH. Sedentary behaviour. Am J Prev Med 2007;33:502– 4. 2. Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Med Sci Sports Exerc 2009;41(5):998 –1005. 3. Owen N, Bauman A, Brown W. Too much sitting: a novel and important predictor of chronic disease risk. Br J Sports Med 2009;43(2):81–3. 4. Jans MP, Proper KI, Hildebrandt VH. Sedentary behaviour in Dutch workers: differences between occupations and business sectors. Am J Prev Med 2007;33(6):450 – 4. 5. Chastin SFM, Granat MH. Methods for objective measure, quantifıcation and analysis of sedentary behaviour and inactivity. Gait Posture 2010;31:82– 6. 6. van Uffelen JGZ, Wong J, Chau JY, et al. Occupational sitting and health risks: a systematic review. Am J Prev Med 2010;39:379 – 88. 7. Levine JA, Lanningham-Foster LM, McCrady SK, et al. Interindividual variation in posture allocation: possible role in human obesity. Science 2005;307(5709):584 – 6. 8. Mummery WK, Schofıeld GM, Steele R, Eakin EG, Brown WJ. Occupational sitting time and overweight and obesity in Australian workers. Am J Prev Med 2005;229:91–7. 9. Healy GN, Wijndaele K, Dunstan DW, et al. Objectively measured sedentary time physical activity, and metabolic risk. Diabetes Care 2008;31(2):369 –71.
www.ajpmonline.org
Evans et al / Am J Prev Med 2012;43(3):293–297 10. Hu FB, Li TY, Colditz GA, Willett WC, Manson JE. Television watching and other sedentary behaviours in relation to risk of obesity and type 2 diabetes mellitus in women. JAMA 2003;289:1785–91. 11. Healy GN, Dunstan DW, Salmon J, Cerin E, Shaw JE, Zimmet PZ, Owen N. Breaks in sedentary time. Diabetes Care 2008;31:661– 6. 12. Healy GN, Matthews CE, Dunstan DW, Dunstan DW, Winkler EAH, Owen N. Sedentary time and cardio-metabolic biomarkers in US adults; NHANES 2003-2006. Eur Heart J 2011;32:590 –7. 13. Thorpe A, Dunstan D, Clark B, et al. Stand up Australia: sedentary behaviour in workers 2008, published by Medibank Private Limited. www.medibank.com.au/Client/Documents/Pdfs/Stand_Up_Australia. pdf. 14. Ryan CG, Grant PM, Dall PM, Granat MH. Sitting patterns at work: objective measurement of adherence to current recommendations. Ergonomics 2011;54(6):531– 8. 15. Chau JY, van der Ploeg HP, van Uffelen JGZ, et al. Are workplace interventions to reduce sitting effective? A systematic review. Prev Med 2010;51:352– 6. 16. Grant PM, Ryan CG, Tigbe WW, Granat MG. The validation of a novel activity monitor in the measurement of posture and motion during everyday activities. Br J Sports Med 2006;40:992–7. 17. Godfrey A, Culhane KM, Lyons GM. Comparison of the performance of the activPALProfessionalphysicalactivityloggertoadiscreteaccelerometer-based activity monitor. Med Eng Phys 2009;29:930–4. 18. Kozey-Keadle S, Libertine A, Staudenmayer J, et al. The feasibility of reducing and measuring sedentary time among overweight, nonexercising offıce workers. J Obes 2012;2012:282303. 19. Gilson ND, Puig-Ribera A, McKenna J, Brown WJ, Burton NW, Cooke CB. Do walking strategies to increase physical activity reduce reported
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sitting in workplaces: a randomised control trial. J Behav Nutr Phys Act 2009;6:43. Gardiner PA, Eakin EG, Healy GN, Owen N. Feasibility of reducing older adults’ sedentary time. Am J Prev Med 2011;41(2):174 –7. Otten JJ, Jones KE, Littenberg B, Harvey-Berino J. Effects of television viewing reduction on energy intake and expenditure in overweight and obese adults: a randomized controlled trial. Arch Intern Med 2009;169(22):2109 –15. Matthews CE, Chen KY, Freedson PS, et al. Amount of time spent in sedentary behaviours in the U.S., 2003–2004. Am J Epidemiol 2008;167(7):875– 81. Chartered Society of Physiotherapy, Fit to work: CSP Public information leaflet 2005; Published by the Chartered Society of Physiotherapy, London, UK. csp.org.uk/uploads/documents/CSP_FTW_inside_v21. pdf. Atlas SJ, Deyo RA. Evaluating and managing acute low back pain in the primary care setting. J Gen Intern Med 2001;16:120 –31. Tudor-Locke C, Burton NW, Brown WJ. Leisure time physical activity and occupational sitting: associations with steps/day and BMI in 54 –59 year old Australian women. Prev Med 2009;48:64 – 8.
Appendix Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.amepre.2012.05.010.
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Purpose: Investigate the effects of point-of-choice (PoC) prompting software, on the computer used at work (PC), to reduce long uninterrupted sedentary periods and total sedentary time at work. Design: Assessor-blinded, parallel group, active-controlled randomized trial. Setting/participants: A convenience sample of offıce workers from Glasgow, United Kingdom. Data were collected April to June 2010, and analyzed October 2010 to June 2011. Intervention: The education group (n⫽14) received a brief education session on the importance of reducing long sitting periods at work. The PoC group (n⫽14) received the same education along with prompting software on their PC for 5 workdays, which reminded them to stand up every 30 minutes.
Main outcome measures: Sitting time was measured objectively using the activPAL™ activity monitor for 5 workdays at baseline and 5 workdays during the intervention. The number and time spent sitting in events ⬎30 minutes’ duration were the main outcome measures.
Results: At baseline, participants spent 5.7⫾1.0 hours/day (76%⫾9%) of their time at work sitting. Of that time, 3.3⫾1.3 hours/day was spent sitting in 3.7⫾1.4 events ⬎30 minutes. There was a signifıcant difference between the groups in the change (intervention to baseline) of both the number (ANCOVA; ⫺6.8%, p⫽0.014) and duration (⫺15.5%, p⫽0.007) of sitting events ⬎30 minutes. During the intervention, compared with baseline, the PoC group reduced the number (paired t-test; ⫺0.11 events/hour, p⫽0.045) and duration (⫺12.2%, p⫽0.035) of sitting events ⬎30 minutes. However, there was no signifıcant difference in total sitting time between groups (⫺4.4%, p⫽0.084). Conclusions: Point-of-choice prompting software on work computers recommending taking a break from sitting plus education is superior to education alone in reducing long uninterrupted sedentary periods at work. Trial registration: This trial was registered at ClinicalTrials.gov NCT01628861. (Am J Prev Med 2012;43(3):293–297) © 2012 American Journal of Preventive Medicine
edentary behavior, time spent sitting/supine,1–5 is a risk factor for morbidity and mortality, independent of physical activity.2,6 –10 In addition, long uninterrupted sedentary events are independently associated with adverse health markers.11,12 Employees sit at work for
⬃77% of the time,13 mostly (51%) accumulated in periods longer than 30 minutes.14 Workplace interventions aiming to reduce sedentary behavior have not been reported, whereas those aimed at increasing physical activity do not decrease self-reported sitting time.15 The current study tested whether using prompting software on a personal computer (PC) used at work, in addition to education, re-
From the School of Health and Life Sciences (Evans, Fawole, Sheriff, Dall, Grant), Glasgow Caledonian University, Glasgow; and the School of Health and Social Care (Ryan), Teesside University, Middlesbrough, United Kingdom Address correspondence to: Philippa M. Dall, PhD, Research Fellow,
School of Health and Life Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, United Kingdom, G4 0BA. E-mail: philippa. [email protected]. 0749-3797/$36.00 http://dx.doi.org/10.1016/j.amepre.2012.05.010
Introduction
S
© 2012 American Journal of Preventive Medicine • Published by Elsevier Inc.
Am J Prev Med 2012;43(3):293–297 293
294
Evans et al / Am J Prev Med 2012;43(3):293–297
duced long uninterrupted sedentary periods and total sedentary time at work compared to education alone.
Methods Design This assessor-blind, parallel group, active-controlled randomized trial compared two groups of offıce workers. The education-only group received an education session on the adverse health effects of sitting for long periods. The point-of-choice (PoC) group received the same education along with prompting software on their PC reminding them to stand every 30 minutes.
Participants A convenience sample of 30 healthy working adults was recruited via poster and e-mail in April–May 2010. All participants worked in an offıce at Glasgow Caledonian University, United Kingdom (UK), and could stand unassisted. There was no racial or gender bias in the selection of participants. Demographic information (age, gender, height, weight, occupational role, smoking status) was recorded. Ethical approval was obtained from Glasgow Caledonian University. Written informed consent was provided.
Baseline Measurement Period Participants wore the activPAL™ (PAL technologies, UK) at work for 5 workdays. The thigh-mounted activPAL provides timestamped acceleration, classifıed into sitting/lying, standing, and walking. The monitor is valid for adults16 –18 and has greater sensitivity to change than other monitors.18 Participants recorded time of arrival (monitor application) and departure (monitor removal) from work in a diary. An e-mail reminding participants to wear the monitor was sent at the start of each workday.
Education Immediately after the baseline measurement period, each participant individually received a short educational talk, read from a script, regarding the health risks of prolonged sitting, stating that standing every 30 minutes could be benefıcial, and a short information leaflet was provided (Appendix A, available online at www.ajpmonline.org).
Group Assignment Random number generation was used to place group assignment into sequentially numbered sealed opaque envelopes by a researcher not delivering the intervention. The next numbered envelope was opened by the researcher, immediately after the education session. Participants were either assigned to the education group (education only) or the PoC group (PoC plus education), and the participant was aware to which group they were allocated.
Prompting Software Participants in the PoC group then additionally had prompting software (MyRestBreak 1.0, ©Vikram Sharma, www.my-restbreak.software.informer.com) loaded onto their PC, which was used during the 5-workday intervention period. An advice window (11X9 cm), reminding participants to take a break, appeared on the monitor, for 1 minute every 30 minutes from the time the PC was
started. The window could not be minimized or moved, but participants could work in any opened windows around it.
Intervention Measurement Period The 5-workday intervention measurement period started immediately, concurrent with the intervention, following the same procedure as for the baseline measurement period.
Data Treatment Data treatment was conducted by a researcher blinded to the allocation of the participant. Data were classifıed into sitting, standing, and walking by proprietary software (version 5.9.1.1, PAL technologies, UK); subsequent data processing was performed by custom software (visual basic for applications in Excel). Reported diary information was used to determine the start/end of each workday. Sedentary periods crossing the reported start/end of the workday were included if most of the sedentary period was within stated work hours and no more than 10 minutes was outside. The minimum data requirement for inclusion was 2 workdays, of at least 4 hours’ duration, in each of the measurement periods. Total time sitting and the number of sitting events (equivalent to the number of breaks in sitting) were used as outcome measures to represent overall sedentary behavior at work. A prolonged sitting event was defıned as ⱖ30 minutes, fıtting the timescale of the intervention. The number of prolonged sitting events and the duration of prolonged sitting events were used to represent prolonged sedentary behavior. Outcome measures were standardized by dividing them by the duration of the workday.
Statistical Analysis Statistical analyses were performed on the standardized outcome measures using SPSS (PASW 18.0). Demographic information and baseline outcome measures were compared between the two groups, using independent samples t-test (normal continuous data, assessed by Kolgorov–Smirnov test) and chi-square test (categoric data). Changes in outcome measure (intervention– baseline) were assessed using paired t-tests, whereas the difference in change in outcome (intervention– baseline) between the two groups was compared using ANCOVA, with the respective baseline as covariate. Between-group standardized effects size and post hoc sample size were calculated.
Results Thirty participants were recruited (Figure 1). Of 278 workdays monitored, 11 were excluded from analysis because of a short reported workday (n⫽3); technical diffıculties (n⫽3); or nonwear (n⫽5). Two participants were excluded because of insuffıcient data. The median number of workdays analyzed was 5 (21 participants) at baseline and 5 (18 participants) during the intervention. Measurement periods ⬍4 days were 2 workdays (two participants, baseline) and 3 workdays (one participant baseline, one participant intervention). The inclusion/exclusion of sitting events crossing the reported start/end of the workday resulted in a net reduction of 77.8 hours (3.9%). The mean (⫾SD) duration of a workday was 7.5⫾0.8 hours/day (median 7.6 hours/day; range 4.0 –12.1 hours/ www.ajpmonline.org
Analysis
Allocation
Enrollment
Evans et al / Am J Prev Med 2012;43(3):293–297
295
Baseline Sedentary Behavior
30 volunteered 30 randomized
15 allocated to PoC prompt and education group
15 allocated to education-only group
1 lost to data analysis due to insufficient data
1 lost to data analysis due to insufficient data
14 analyzed
14 analyzed
Figure 1. CONSORT flow diagram
At baseline, participants spent (M⫾SD [range]) 5.7⫾1.0 hours/day (76%⫾9% [2.4 –9.8 hours/day, 46%–96%]) at work sitting, in 26⫾10 events (3.4⫾1.2 events/hour [7– 67, 0.9 –18.3 events/hour]). Participants had 3.7⫾1.4 (0.49⫾0.18 events/hour [0 – 8, 0.00 –1.21 events/hour]) prolonged sitting events, which lasted 3.3⫾1.3 hours/day (55%⫾20% [0.0 –7.2 hours/day, 0%–97%]). There were no statistical differences between groups at baseline.
Effect of the Intervention on Sedentary Behavior
PoC, point-of-choice
day). Participants had normal BMI (23.7⫾3.5 vs 23.6⫾2.8, PoC/Ed group); were predominantly female (n⫽11/11); and worked as administrators (n⫽4/3), researchers (n⫽5/7), or lecturers (n⫽5/4); all were nonsmokers. The PoC group (aged 49⫾8 years) was older than the education group (aged 39⫾10 years; p⫽0.008).
The only within-group differences were for the number (⫺0.11 events/hour) and duration (⫺12.2%) of prolonged sitting events (Table 1). There was no betweengroup difference (estimated marginal mean difference PoC– education [95% CI], p-value) in total sitting time (⫺4.4% [⫺9.6%, 0.6%], p⫽0.084). There were signifıcant between-group differences in the total number of sitting
Table 1. Sedentary behavior of participants
Total sitting time (hours/day [%])
Group
BL
Int
Change (Int-BL)
Difference (PoC-Ed)
PoC⫹Ed
5.9⫾1.0
5.6⫾1.1
⫺0.3⫾0.9
⫺0.3⫾0.3
(78.1⫾6.9)
(75.0⫾9.9)
(⫺3.1⫾7.0)
(⫺4.4⫾2.4)
5.6⫾1.0
5.7⫾0.9
0.1⫾0.6
(74.0⫾11.0)
(76.4⫾8.0)
(2.4⫾6.6)
26⫾11
28⫾9
1.6⫾5.3ⴱ
4.3⫾1.9
(0.3⫾0.5)
(0.5⫾0.2)
Ed-only
Number of sitting events (events/ day [events/hour])
PoC⫹Ed
(3.4⫾1.1) Ed-only
Number of prolonged sitting events (events/day [events/hour])
PoC⫹Ed
Ed-only
Duration of prolonged sitting events (hours/day [%])
PoC⫹Ed
Ed-only
(3.7⫾1.0)
ⴱ
23⫾10
⫺2.4⫾5.7
(3.3⫾1.3)
(3.1⫾1.4)
(⫺0.3⫾0.7)
3.5⫾1.4
2.7⫾1.3
⫺0.8⫾1.6ⴱ
(0.47⫾0.19)
(0.36⫾0.19)
(⫺0.11⫾ 0.19)
25⫾9
⫺1.1⫾0.4ⴱⴱ (⫺0.14⫾0.05)
ⴱ
3.8⫾1.4
3.9⫾1.2
0.1⫾0.9
(0.50⫾0.48)
(0.52⫾0.15)
(0.02⫾0.12)
3.1⫾1.2
2.3⫾1.4
⫺0.8⫾1.4ⴱ
(51.9⫾19.3)
(39.7⫾21.2)
(⫺12.2⫾ 19.3)
⫺1.0⫾0.4ⴱⴱ (⫺15.4⫾5.3)
ⴱ
3.5⫾1.5
3.6⫾1.3
0.1⫾0.7
(58.5⫾20.5)
(59.7⫾17.4)
(1.2⫾7.9)
Note: Data shown in each cell are M⫾SD for both the actual value of the outcome measure per day and for the standardized outcome measure (shown in parentheses). All statistics were performed on standardized data. Outcome measures of time spent sitting have units of hours/day (% of workday); outcome measures of events have units of events/day (events per hour at work). Prolonged sitting was defined as sitting continuously for ⬎30 minutes. The PoC⫹Ed group received a computer prompt to stand every 30 minutes plus verbal and pamphlet education. The Ed group received verbal and pamphlet education. Bold indicates significance. *Difference in outcome measure significantly different between the groups (p⬍0.05) **Outcome measure significantly different at intervention compared to baseline (p⬍0.05) BL, baseline measurement period; Change (Int-BL), within-group change in outcome at the intervention measurement period compared to baseline; Ed, education; Difference (PoC-Ed), between-group difference in outcome measure of the change (intervention– baseline); Int, intervention measurement period; PoC, point-of-choice
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events (0.54 events/hour [0.07, 1.02], p⫽0.027) and for the number (⫺0.14 events/hour [⫺0.25, ⫺0.03], p⫽0.012) and duration (⫺15.4% [⫺26.2%, ⫺4.5%], p⫽0.007) of prolonged sitting events. Standardized effect sizes between groups of the change in outcome (intervention– baseline) were small (number of sitting events, 0.44) or moderate (total sitting time, 0.60; number of prolonged sitting events, 0.69; total time sitting in prolonged events, 0.68). Post hoc calculations indicated that 44 individuals per group would be required to show a signifıcant (80% power, p⫽0.05) difference between groups in total sitting time.
Discussion Measured objectively, there was no difference on total time spent sitting. However, both the number of and the time spent sitting in prolonged sitting periods (⬎30 minutes’ duration) were reduced in the PoC-plus-education group and differed in comparison to the lack of change in the education-only group. To our knowledge, this is the fırst RCT to investigate the effects of an intervention specifıcally targeted to reduce adverse sedentary behavior in the workplace. One workplace intervention aiming to increase physical activity through incidental activity demonstrated a nonsignifıcant self-reported reduction in sitting at work of 15 minutes,19 a similar absolute level to the present study (17 minutes). Three nonworkplace interventions aimed at reducing sedentary behavior demonstrated pre–post reductions in objectively measured sitting from 3.2% to 4.3%.18,20,21 These reductions are of a similar magnitude to that of the PoC group in the current study (⫺3.1%), despite the studies using different activity monitors (activPAL18; actigraph20; SenseWear armband21) and interventions (behavioral18,20; TV-lockout21), in different populations (older adults20; overweight/obese adults18,21). Only one of these studies included a control group.21 The PC prompt used in the present study was related to the time the PC was switched on in the morning, and not necessarily to the sitting behavior of the participant. Despite this, prolonged sitting was reduced in the PoC group compared to the education-only group, although whether participants were responding specifıcally to the prompts, or using them as general reinforcement to the education is unclear.
Limitations and Strengths A limitation of the present study is its small sample size. The PoC group was signifıcantly older than the education group. Adults tend to become more sedentary as they get older22; however, the potential effect of age on compliance with the intervention is unclear. There are no
evidence-based guidelines on the appropriate maximum period of sitting duration for health. The recommendation to stand every 30 minutes was selected from the range of informal recommendations that exist (20 minutes,23 30 minutes,24 55 minutes3). There is no evidence that altering sedentary patterns to fıt this recommendation will have health benefıts. The duration of the intervention was short (3–5 workdays) and there was no long-term follow-up. There was no process evaluation to ascertain if the intervention was delivered as intended or whether participants found the intervention useful. Strengths of this paper were the novel intervention paradigm, the assessment of patterns of sedentary behavior,5,14 and the use of an objective measurement of sedentary behavior.16,19,22,25
Conclusion A health promotion intervention specifıcally targeting sedentary behavior at work—point-of-choice prompts on work computers reminding individuals to take a 1-minute break from sitting every 30 minutes—reduced the number of, and time spent in, prolonged (⬎30 minutes) uninterrupted sitting periods compared to education alone. This study was funded by the School of Health, Glasgow Caledonian University, and formed the dissertation project for Masters of Rehabilitation Science of Rhian Evans, Henrietta Fawole, and Stephanie Sheriff. No fınancial support was received from any commercial company. No fınancial disclosures were reported by the authors of this paper.
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Appendix Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.amepre.2012.05.010.
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