Participants were recruited from ongoing population-based diabetes screening programs in Leicester, U.K., between September 2006 and March 2007; the study was completed in April 2008. Overweight or obese individuals (BMI ≥25 or ≥23 kg/m2
for South Asians) with screening-detected IGT (7
) were contacted by letter and follow-up telephone call by a member of their screening team and invited to take part in the study. Individuals were recruited into the study within 12 months of their screening visit. As part of the screening programs, all individuals had their physical activity levels assessed by the short version of the international physical activity questionnaire (IPAQ) (8
). Individuals who reported taking steroids were excluded.
All applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research. This study was approved by the Leicestershire, Northamptonshire, and Rutland National Health Service Research Ethics Committee in June 2006.
Treatment regimens and randomization
Participants were randomly assigned, using a block design, to receive either usual care, the PREPARE program, or the PREPARE program without pedometer use and were stratified by age and sex. Participant random assignment was conducted using opaque envelopes and a randomly generated number sequence by a member of our research team with no prior knowledge of recruited individuals other than their age and sex. Participants were informed of their allocated group by a member of our research team once their baseline measurements were completed.
The theoretical underpinning, design, and content of the PREPARE program have been described in detail elsewhere (5
). In brief, it is a single-session group-based education program. The program is 180 min long; 105 min are dedicated to addressing the causes, complications, timeline, and identity of IGT and 75 min are targeted to addressing the perceived effectiveness of exercise as a treatment for IGT, walking self-efficacy beliefs, barriers to walking, and self-regulatory strategies. The program has a written curriculum, modeled on the person-centered philosophy and learning techniques developed for the Diabetes Education and Self-Management for Ongoing and Newly Diagnosed (DESMOND) program (9
), an established nationally available 6-h structured educational program designed to promote lifestyle change and self-management for those with newly diagnosed type 2 diabetes in the U.K.
As part of the program, participants were provided with a pedometer (SW-200; Yamax, Tokyo, Japan) and encouraged to set personalized steps-per-day goals based on their baseline ambulatory activity level. Sedentary participants were encouraged to increase their activity levels by at least 3,000 steps per day, equivalent to ~30 min of walking (12
). Those achieving >6,000 steps per day were encouraged to try to reach at least 9,000 steps per day, an amount that is likely to include 30 min of walking activity in addition to usual daily activity (12
). Those achieving >9,000 steps per day were encouraged to at least maintain their current activity levels and were informed that health benefits could be achieved by increasing their activity levels further. Goal attainment was encouraged through the use of proximal objectives, such as increasing ambulatory activity by 500 steps per day every 2 weeks. Participants were enabled to set an action plan detailing where, when, and how their first proximal goal would be reached and encouraged to repeat this process for each new proximal goal. They were also encouraged to wear their pedometer on a daily basis and to self-monitor their ambulatory activity using a steps-per-day log.
PREPARE program without pedometer use
This group received the PREPARE program, but instead of receiving pedometers, participants were encouraged to set time-based goals designed to match the advice given to the pedometer group. Sedentary individuals were encouraged to try to achieve at least 30 min of moderate-intensity physical activity per day. Those already achieving 30 min of moderate-intensity physical activity were encouraged to at least maintain their current activity levels and were informed that health benefits could be achieved by increasing their activity levels further. As with the pedometer group, participants were encouraged to set proximal goals, such as increasing moderate-intensity activity by 5 min/day every 2 weeks, form action plans, and record their daily activity levels. Individuals wishing to set vigorous-intensity activity goals were advised that they should consult their general practitioner before commencing the program.
Intervention delivery and follow-up
Both versions of the PREPARE program were delivered by two educators trained through the DESMOND program. Programs were delivered at the Diabetes Research Unit, Leicester Royal Infirmary, U.K., within 1 month of baseline measurements. Individuals in both intervention groups also received a brief (10-min) review of progress during their 3- and 6-month clinical measurement session delivered by the same educators who had delivered the initial educational program.
Participants randomly assigned to the control group were sent a brief information sheet in the mail, detailing the likely causes, consequences, symptoms, and timeline associated with IGT, along with information about how physical activity can be used to treat/control the condition.
All outcomes were measured at baseline and at 3, 6, and 12 months; 2-h glucose was the primary outcome, and all other outcomes were secondary.
At their baseline appointments, participants underwent an oral glucose tolerance test (fasting and 2-h glucose). Participants arrived at their appointment after a 12-h fast and 24 h of avoiding vigorous exercise. Those with a diagnosis type 2 diabetes at baseline were excluded from the study (7
). All biochemical analyses were conducted blinded to treatment group.
Plasma glucose was measured using a glucose oxidase method on the Beckman AutoAnalyzer (Beckman, High Wycombe, U.K.). Serum cholesterol was analyzed using a cholesterol enzymatic assay (Abbott Clinical Chemistry, Chicago, IL). HDL cholesterol was analyzed using the ultra-HDL assay (Abbott Clinical Chemistry). Serum triglyceride was analyzed using the triglyceride glycerol phosphate oxidase assay (Abbott Clinical Chemistry). Biochemical measurements were performed in the same laboratory located within Leicester Royal Infirmary using stable methodology standardized to external quality assurance reference values.
Physical activity was measured objectively by pedometer and subjectively by questionnaire. Sealed piezoelectric pedometers with a 7-day memory (NL-800; NEW-LIFESTYLES, Lee's Summit, MO) were used to measure ambulatory activity. These pedometers were different from the motivational instruments used in the primary intervention condition and have been shown to be more accurate than traditional spring-levered pedometers in overweight and obese individuals (13
). For the purposes of this study at least 3 valid days of data were required; a valid day constituted at least 12 h of wear time.
Physical activity was also measured using the long last-7-days self-administered format of the IPAQ. This questionnaire provides a measure of walking and other moderate- to vigorous-intensity activities carried out for ≥10 continuous minutes at work, in the home, as transport, and during leisure time. The IPAQ has been shown to have reasonable validity compared with accelerometer data (ρ ~0.4) and test-retest reliability (ρ ~0.7) in the U.K. (8
Perceptions and perceived knowledge of IGT.
Perceptions and perceived knowledge of IGT were measured with the validated brief illness perceptions questionnaire (14
). This instrument was used to measure five cognitive illness representations (consequences, timeline, personal control, treatment, and symptom load attributed to IGT), two emotional representations (concern and negative emotion affect attributed to having IGT), and perceived knowledge of IGT. Each item was answered using an 11-point Likert scale.
Participants' confidence in their ability to exercise in the face of five commonly identified barriers (tired, bad mood, bad weather, lack of time, and holiday) was measured using an 11-point Likert scale (15
Demographic and anthropometric data
Arterial blood pressure was measured in the sitting position (Omron Healthcare, Henfield, U.K.); three measurements were obtained and the average of the last two measurements was used. Body weight (Tanita TBE 611 scale; Tanita, West Drayton, U.K.), waist circumference (midpoint between the lower costal margin and iliac crest), and height were also measured to the nearest 0.1 kg and 0.5 cm, respectively. Information on current smoking status, medication history, and ethnicity were obtained by self-report.
Based on a power of 80%, a significance of 0.05, and a SD of 1 mmol/l and allowing for a 50% dropout rate (noncompleters and those diagnosed with type 2 diabetes at baseline), 34 participants were required per group to detect a 1 mmol/l difference in 2-h glucose levels between each intervention group and control group at 12 months. Those not attending the final 12-month follow-up measurement session and those diagnosed with type 2 diabetes at baseline were excluded from the analysis. Those diagnosed with type 2 diabetes at 3 and 6 months (n = 4) were treated according to the screening studies from which they were recruited and had subsequent follow-up data imputed using their last observation carried forward. To have numeric parity across time points, missing biochemical, pedometer, and anthropometric data at 3 months (n = 2) and 6 months (n = 2), resulting from those not attending all intermediary follow-up sessions, were imputed using the next observation carried backward. All individuals included in the analysis were analyzed in the group to which they were assigned.
Between-group comparisons of change in measured outcomes at 3, 6, and 12 months were conducted using ANCOVA procedures; baseline data were included as a covariate. Each intervention group was compared with the control group using simple a priori contrasts; because this study had one primary hypothesis, adjustment was not made for multiple group, time, or outcome comparisons. Nonetheless, secondary outcomes were interpreted with caution and in relation to the overall pattern of results. All variables were checked for normality using the Kolmogorov-Smirnov test and visual inspection after the removal of extreme outliers (a value at least 4 SD from the mean). Tests were two-sided; P < 0.05 was considered significant. All analysis was carried out with SPSS 14.0 for Windows (SPSS, Chicago, IL).