Pedometer-determined ambulatory activity in individuals with type 2 diabetes

Abstract

This cross-sectional study presents the first normative data on pedometer-determined ambulatory activity, defined as steps/day, in 160 (98 males, 62 females; age=52.4±5.3 years; BMI=32.3±5.7) free-living individuals with type 2 diabetes. Participants took 6662±3077 steps per day, less than that reported in nondiabetic samples and more than that reported for samples living with more restrictive chronic conditions including claudication, joint replacement, chronic obstructive lung disease, and chronic heart failure. Steps/day and BMI were inversely and significantly correlated (r=−0.27, P<0.01). Further, there was a significant difference between BMI categories (from normal weight to obesity class III) with regard to steps/day (F=2.96, P<0.05). The difference was most apparent between the highest obesity classes (II and III) and normal weight categories. This data is useful for sample comparison purposes. In addition the standard deviation or variance estimates can be used to calculate samples sizes for intervention efforts. Objective quantification of ambulatory activity via simple and inexpensive pedometers permits researchers and practitioners to easily screen for level of activity along a continuum. This study opens the door for future research and clinical applications including identifying threshold values related to important health outcomes and evaluating incremental change due to various interventions in this population.

Introduction

Despite the well-known multiple benefits of a physically active lifestyle, individuals with type 2 diabetes are generally described as sedentary. The empirical evidence to support this characterization is meager, however. For instance, a review of survey data from the 1990 United States National Health Interview Survey found that 66% of individuals with diabetes (both type 1 and type 2) reported no participation in regular leisure-time physical activity, compared with 59% of nondiabetics, although this difference was negated when activity limitations were considered [1]. These distinct populations did not differ on mean number of bouts of exercise, average number of minutes per bout of exercise, or mean total weekly hours of exercise [1]. Differences were noted, however, in activity choices. People with diabetes were more likely to engage in walking and less likely to engage in more vigorous activities (e.g. jogging, dancing, tennis, bicycling, skiing, weight-lifting, etc.) than were people without diabetes [1]. However, walking is considered the least reliably recalled physical activity [2], [3], [4]. In addition, most, if not all, self-report instruments suffer from restrictive floor effects that limit researchers to describing the percentage of individuals who fail to register on the preferred instrument [5]. For example, Hays and Clark [6] recently reported that almost 55% of a sample of 260 individuals with type 2 diabetes reported zero minutes of weekly physical activity in response to questions about walking behaviors. Surely, these individuals are doing some level of physical activity that apparently continues to escape our best efforts at quantification through self-report questionnaires. If we are to document the physical activity patterns of this population, as well as investigate how changes in habitual behaviors impact on important health outcomes, then it is imperative that we accurately quantify walking behaviors.

The use of simple and inexpensive pedometers to quantify physical activity, specifically ambulatory activity, is a recent development [5], [7], [8], [9], [10], [11]. Compared with accelerometers, pedometers are less expensive and more practical for both research and clinical applications [5]. In addition to being used to quantify habitual walking activity, pedometers may be useful motivational tools to encourage individuals with type 2 diabetes to increase walking behaviors [12], [13]. Researchers and clinicians focused on type 2 diabetes require normative data to assist with interpretation of pedometer data. In addition users want to know how pedometer output (steps/day) is related to health indicators. The purpose of this paper is to present, as a starting point, descriptive data from the first pedometer-assessed ambulatory activity database of individuals with type 2 diabetes. This database also permits an examination of the relationship between steps/day and body mass index or BMI (an indicator of body composition), as well as self-reported frequency of exercise, perceived health status, and perceived readiness (i.e. stages of change) for exercise.