Can the Onset of Type 2 Diabetes Be Delayed by a Group-Based Lifestyle Intervention in Women with Prediabetes following Gestational Diabetes Mellitus (GDM)? Findings from a Randomized Control Mixed Methods Trial

Table 1

Primary and secondary outcome measures and measurement time points.

Outcome	Definition and measurement	Timepoint measured
		Baseline	EOP	1-year
Primary outcome
Fasting plasma glucose (FPG 0-hour)	Reduction in FPG (0-hour) on a 75 gram oral glucose tolerance test (OGTT)	✓		✓
Secondary outcomes
Glucose tolerance (GT2 hour)	Reduction in postload glucose tolerance (2-hour) on a 75 gram OGTT	✓		✓
Insulin resistance (IR)	Reduction in IR as measured by Homeostasis Model Assessment (HOMA2- IR), using fasting glucose and insulin values [33] on a 75 gram OGTT	✓		✓
Lipid profile	(i) Reduction in triglycerides, LDL, and total cholesterol; (ii) Improvement in HDL cholesterol	✓	✓	✓
Diet adherence	Improvement in overall Mediterranean Diet Score, a composite diet index based on the traditional Mediterranean dietary pattern [34]	✓	✓	✓
Weight and shape	(i) Reduction in weight (kilograms); (ii) Reduction in waist circumference (CM)	✓	✓	✓
Physical activity and fitness	(i) Total exercise per week (frequency × duration); (ii) Change in cardiorespiratory fitness measured using maximal metabolic equivalent (METmax) on an objective physical fitness test (Chester Step Test) [35]	✓	✓	✓
Mood	(i) Positive mental health: 4 items from RAND SF-36 questionnaire addressing affective aspects of wellbeing [21]; (ii) Nonspecific psychological distress: 5 items from the Mental Health Index-5 (MHI-5) in the RAND SF-36 questionnaire [21]; (iii) Depression, anxiety, and stress: 21 items from Depression, Anxiety, and Stress Scale (DASS-21) [22]	✓		✓
Cognition	(i) Perceived social support: Multidimensional Scale of Perceived Social Support from family, friends, and a significant other [25]; (ii) Motivation to change: a one item forced choice question with 5 options to assess current stage of change [13]; (iii) Diabetes-related self-efficacy: 18-item assessment of confidence to engage in exercise and healthy eating under different “barrier” conditions [13]	✓		✓
Wellbeing	(i) General health: stand-alone measure of self-rated health included in the Irish Survey of Lifestyle, Attitudes, and Nutrition (SLÁN), 2007 [23]; (ii) Quality of life: single-item assessment included in SLÁN 2007 [23]	✓		✓