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Trial registered on ANZCTR


Registration number
ACTRN12616000945426
Ethics application status
Approved
Date submitted
12/07/2016
Date registered
18/07/2016
Date last updated
7/07/2017
Type of registration
Prospectively registered

Titles & IDs
Public title
Glucose lowering effect Of walking breaks in pregnancy study
Scientific title
Understanding the effect of breaking up sitting on postprandial blood glucose in women at risk of gestational diabetes mellitus
Secondary ID [1] 288809 0
Nil
Universal Trial Number (UTN)
Trial acronym
GLOW (Glucose Lowering effect Of Walking breaks) in pregnancy study
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Gestational Diabetes Mellitus 298077 0
Condition category
Condition code
Metabolic and Endocrine 298240 298240 0 0
Diabetes
Reproductive Health and Childbirth 299465 299465 0 0
Fetal medicine and complications of pregnancy

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
In this cross-over trial, participants will complete two laboratory-based conditions, separated by a 7 day wash out. The experimental condition involves 4.5 hours of prolonged sitting with intermittent bouts of gentle walking. Participants will remain seated for the initial 30 minutes (steady state period, after which they will consume a 75g glucose load and will complete a 2 minute bout of gentle walking every 20 minutes for the remaining 4 hours (total duration of walking = 12 x 2 minute bouts = 24 minutes). All activities will take place in a controlled laboratory environmental under the supervision of trained clinical research staff. During the condition, participants will be permitted to watch television, DVDs or read.
Intervention code [1] 294261 0
Prevention
Intervention code [2] 294262 0
Lifestyle
Comparator / control treatment
In a controlled laboratory environment, participants will complete 4.5 hours of prolonged sitting without breaks (only toilet breaks permitted). Participants will sit in a comfortable chair and will consume a 75g glucose load after an initial 30 minute steady state period. Participants will be permitted to watch television programs, DVDs or read during the condition, and all activities will be supervised and recorded by clinical research staff.
This study is a non-randomised cross-over trial, whereby the participant will complete both the experimental and control conditions. Women at risk of gestational diabetes mellitus will first undergo the control condition, which involves the recommended screening for gestational diabetes mellitus. According to current guidelines, diagnosis of gestational diabetes mellitus is based on any one of the following: Fasting plasma glucose between 5.1 and 6.9mmol/l; a 1-hour plasma glucose post 75g oral glucose load greater than 10.0mmol/l; or a 2-hour plasma glucose post 75g oral glucose between 8.5 and 11.0mmol/l at 24-28 weeks gestation. This study will follow a non-randomised design to expedite management of hyperglycaemia in individuals with gestational diabetes mellitus who require immediate medical attention.
Control group
Active

Outcomes
Primary outcome [1] 297735 0
Postprandial glycaemic response calculated as mean area under the curve (AUC) from half hourly venous blood sampling over two 4.5 hour experimental conditions
Timepoint [1] 297735 0
Blood samples for assessment of plasma glucose will be collected half-hourly until the end of the 4.5 hr period during each experimental conditions
Secondary outcome [1] 322063 0
Postprandial insulin response calculated as mean area under the curve (AUC) from half hourly venous blood sampling over two 4.5 hour experimental conditions
Timepoint [1] 322063 0
Blood samples for assessment of plasma insulin will be collected half-hourly until the end of the 4.5 hr period during each experimental conditions
Secondary outcome [2] 322064 0
Changes in resting blood pressure using automated oscillometric blood pressure monitor
Timepoint [2] 322064 0
In each experimental condition, blood pressure will be measured every hour in a resting state

Eligibility
Key inclusion criteria
Eligibility includes women 24-28 weeks gestation and at increased risk for developing gestational diabetes mellitus identified by a validated risk prediction tool (Monash GDM score greater than 4).
Minimum age
18 Years
Maximum age
No limit
Sex
Females
Can healthy volunteers participate?
No
Key exclusion criteria
Exclusion will be based on: less than 18 years of age, multiple pregnancy, diagnosed type 1 or 2 diabetes, a BMI greater than 45 kg/m^2, pre-existing chronic medical conditions, absolute contraindications to aerobic exercise during pregnancy according to the American College of Obstetricians and Gynecologists (ACOG) guidelines, currently sitting for less than 5 hours per day, regularly engaged in moderate-intensity exercise more than 150 min/week for more than 3 months, current smoker or use of nicotine replacement therapy, and non-English speaking.

Study design
Purpose of the study
Prevention
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?



The people analysing the results/data
Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
Power calculations have been made in relation to the primary outcome measures of postprandial glucose (venous collections). Based on our own data (1) and previously published work (2) , we have estimated that a sample size of 22 is needed to detect a between treatment difference of 0.9mmol/L with a minimum power of 80% and a probability of 0.05 (2-tailed test). This is based on the assumption that the within-patient standard deviation of the response variable is 1.04. As a safeguard and using our experience from previous behavioural interventions, we will over-sample to cover an estimated attrition rate of 15%. Thus, 25 participants will be recruited.

Generalized linear mixed models (GLMMs) with random intercepts will be used to evaluate the differential effects of the experimental conditions on the outcomes. All models will include a binary variable indicating the experimental condition, adjusted for potential period effects and period-dependent confounders (baseline values for the outcome of interest, dietary intake and physical activity). Given that the study uses a balanced orthogonal design and substantial imbalances due to dropout are unlikely, it will not be necessary to adjust for subject-level covariates (e.g., age). GLMMs are appropriate for correlated data (repeated measures) with various distributional assumptions and can easily accommodate missing data. A probability level of 0.05 will be adopted.

References

1. Larsen RN, Kingwell BA, Robinson C, Hammond L, Cerin E, Shaw JE, et al. Breaking up of prolonged sitting over three days sustains, but does not enhance, lowering of postprandial plasma glucose and insulin in overweight and obese adults. Clinical science. 2015;129(2):117-27.
2. Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring, Md). 2013;21(12):2504-12.

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
25/07/2016
Actual
Date of last participant enrolment
Anticipated
13/04/2018
Actual
Date of last data collection
Anticipated
4/05/2018
Actual
Sample size
Target
25
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
VIC
Recruitment hospital [1] 8503 0
Mercy Hospital for Women - Heidelberg
Recruitment postcode(s) [1] 16596 0
3084 - Heidelberg

Funding & Sponsors
Funding source category [1] 293172 0
Government body
Name [1] 293172 0
National Health and Medical Research Council (NHMRC)
Country [1] 293172 0
Australia
Primary sponsor type
Individual
Name
Professor David Dunstan
Address
Physical Activity Laboratory
Baker IDI Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne VIC 3004
Country
Australia
Secondary sponsor category [1] 291966 0
None
Name [1] 291966 0
Address [1] 291966 0
Country [1] 291966 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 294661 0
Alfred Health Human Ethics Committee
Ethics committee address [1] 294661 0
Office of Ethics & Research Governance
Alfred Health
55 Commercial Road
Melbourne VIC 3004
PO Box 315 Prahran
VIC 3181 Australia
Ethics committee country [1] 294661 0
Australia
Date submitted for ethics approval [1] 294661 0
06/04/2016
Approval date [1] 294661 0
21/06/2016
Ethics approval number [1] 294661 0
HREC 163/16
Ethics committee name [2] 298148 0
Mercy Health Human Research Ethics Committee
Ethics committee address [2] 298148 0
6th Floor, Mercy Hospital for Women,
163 Studley St
Heidelberg VIC 3084
Ethics committee country [2] 298148 0
Australia
Date submitted for ethics approval [2] 298148 0
14/12/2016
Approval date [2] 298148 0
28/03/2017
Ethics approval number [2] 298148 0
2017-002

Summary
Brief summary
The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide, with current Australian prevalence rates estimated to be between 13-16%. The primary goal of GDM management is to prevent hyperglycaemia, as there is a clear dose-dependent relationship between increased plasma glucose levels during pregnancy and adverse outcomes for both the mother and child. Compliance rates for exercise intervention trials in pregnant women are generally poor (reporting adherence as low as 16-55%).

Furthermore, the majority of pregnant women do not reach the recommended levels of physical activity; and overall physical activity levels tend to decrease throughout pregnancy (particularly in caregiving, outdoor, household and recreational activities). The lack of adherence to an exercise regime could be due to feelings of tiredness and increasing immobility as pregnancy progresses, which would limit the ability or motivation for women to maintain exercise efforts for more than 10 min at a time, particularly for women who are not normally active. In light of the fact that brief (2-3 minutes), regular (every 20-30 minutes), light ambulatory activities have been demonstrated to be effective in improving postprandial glucose control in overweight/obese and T2D patients, consideration of the “breaks in sitting” approach may be appropriate for women at risk for or diagnosed with GDM. Given that post-challenge glucose is considered a surrogate for postprandial glycaemia, there is value in examining the effect of breaking up sitting in the context of routine screening for GDM. Based on past studies done within our laboratory, we anticipate that breaking up sitting will lower postprandial glucose responses compared to prolonged sitting without breaks, and may even prevent levels
from entering the GDM range. The results of this trial will help inform the design and development of a larger, chronic study looking at breaking up sitting to improve pregnancy outcomes for mothers and offspring.
Hypothesis: We hypothesise that regular, light intensity ambulatory breaks in sitting (2 minutes every 20 minutes) will lower post-OGTT glucose and insulin responses in women at risk for developing GDM, compared to sitting-only control.
Study Design: A cross-over trial, involving women at risk of GDM, of two laboratory-based interventions undertaken during a standard 75g oral glucose tolerance test.
Outcomes: Primary outcomes – postprandial glycaemic response calculated as the incremental area under the curve (iAUC) from half hourly blood sampling over a 4 hour period. Secondary outcomes – postprandial insulin response calculated as iAUC and mean blood pressure.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 64530 0
Prof David Dunstan
Address 64530 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne VIC 3004
Country 64530 0
Australia
Phone 64530 0
+61 3 8532 1873
Fax 64530 0
+61 3 8532 1150
Email 64530 0
[email protected]
Contact person for public queries
Name 64531 0
Megan Grace
Address 64531 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne VIC 3004
Country 64531 0
Australia
Phone 64531 0
+61 3 8532 1855
Fax 64531 0
+61 3 8532 1150
Email 64531 0
[email protected]
Contact person for scientific queries
Name 64532 0
Robyn Larsen
Address 64532 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Institute
Level 4, Alfred Centre
99 Commercial Road
Melbourne VIC 3004
Country 64532 0
Australia
Phone 64532 0
+ 61 3 85321859
Fax 64532 0
+61 3 8532 1150
Email 64532 0
[email protected]

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