Abstract
Purpose
This study describes baseline physical activity (PA) patterns of individuals with type 2 diabetes mellitus enrolled in the multi-center Look AHEAD Study using an objective measure of PA (accelerometry).
Methods
2,240 participants (age = 59.0±6.8 years; BMI = 36.5±6.0 kg/m2) with type 2 diabetes mellitus (T2DM) provided data for this sub-study. Participants were instructed to wear an accelerometer during waking hours over 7 days. Accelerometry data were analyzed to identify periods meeting the criteria of ≥3 METs per minute for ≥10 minutes (MVPA) and ≥6 METs per minute for ≥10 minutes (VPA). Self-reported PA was also assessed with a questionnaire. Accelerometry and self-reported PA data were compared across categories of BMI, sex, race, age, fitness, diabetes medication usage, and history of cardiovascular disease
Results
Self reported PA was lower at higher levels of BMI, was higher in males, was lowest for African-American/Black, and positively associated with fitness. Multivariate analyses for accelerometer measured MVPA and VPA showed that more PA bouts per day, minutes per bout, METs per minute, and MET-minutes were associated with higher fitness. For MVPA, bouts per day were higher in men, and METs per minute were higher in women. For VPA, bouts per day was positively associated with increasing age and differed by race/ethnicity. METs per minute were significantly lower at higher levels of BMI and in women. Diabetes medication usage and history of cardiovascular disease were not associated with patterns of physical activity examined.
Conclusions
Results provide information of factors that contribute to PA patterns in adults with T2DM when PA is assessed using both objective and subjective measures. These data may inform interventions to improve PA in adults with T2DM.
Keywords: exercise, obesity, accelerometry
INTRODUCTION
Based on recent estimates, approximately 7.8% of the population in the United States has type 2 diabetes mellitus, with this including 17.9 million diagnosed and 5.7 undiagnosed cases (10). Moreover, when using an age criterion of ≥20 years or ≥60 years, the prevalence is estimated to be 10.7% and 23.1%, respectively (10). This creates a significant public health burden due to the direct cost of its treatment, the indirect cost associated with it, and its link to increased mortality due to cardiovascular disease (10, 16, 18).
The recent Physical Activity Guidelines Advisory Committee Report concluded that there is evidence that physical activity is important in the treatment of type 2 diabetes as it improves glycemic and cardiovascular risk factor control (21). For example, a meta-analysis conducted by Thomas et al. (19) concluded that repeated bouts of physical activity improve glycemic control in persons with type 2 diabetes. Observational cohort studies have associated higher levels of walking and leisure time physical activity with reduced cardiovascular disease incidence and mortality (5).
The vast majority of studies examining the influence of physical activity on diabetes treatment and related complications have been based on self-report with limited objective data on the daily patterns of physical activity. An objective measure of physical activity using accelerometry was included in the multi-center Look AHEAD Study on individuals with type 2 diabetes from 8 of the 16 clinical sites (14). The availability of these data provides an opportunity to objectively examine patterns of physical activity in this population and to determine factors that may influence participation in physical activity.
The purpose of this study is to describe the patterns and correlates of physical activity in individuals with type 2 diabetes mellitus enrolled in the multi-center Look AHEAD Study using an objective measure of physical activity (accelerometry). Specifically, we examine whether patterns of physical activity among persons with type 2 diabetes vary according to levels of BMI, sex, ethnicity/race, age, baseline fitness, diabetes medication, and presence of cardiovascular disease.
METHODS
Participants
Participants for this study are a subgroup of participants who completed baseline testing prior to being randomized into the multi-center Look AHEAD Study, which is a trial examining the effect of weight loss on the primary and secondary prevention of cardiovascular disease in obese adults with type 2 diabetes (14). The Look AHEAD Study included 5,145 participants recruited across 16 clinical sites in the United States, with 8 of the sites including 2,627 participants enrolled in a sub-study to assess physical activity using accelerometry. Descriptive data for this subgroup of participants are presented in Table 1.
Table 1.
Baseline Characteristics of Participants with Valid Baseline Accelerometry Data (N=2145)
| Variable | Participants with Valid Accelerometry Data (N=2145) | Total Look AHEAD Study Sample (N=5145) |
|---|---|---|
| Age | 59.0 ± 6.8 | 58.7 ± 6.8 |
| Weight (kg) | 102.9 ± 19.2 | 100.7 ± 19.3 |
| Height (cm) | 168.1 ± 9.5 | 167.2 ± 9.7 |
| Body mass index (kg/m2) | 36.4 ± 6.0 | 35.9 ± 5.9 |
| Waist Circumference (cm) | 115.4 ± 14.5 | 113.9 ± 14.0 |
| Hemoglobin A1c% | 7.2 ± 1.1 | 7.3 ± 1.2 |
| Fasting glucose (mg/dL) | 151.7 ± 44.5 | 153.2 ± 45.7 |
| Duration of diabetes (years) | 6.9 ± 6.5 | 6.8 ± 6.5 |
| Fitness (Maximal METs) | 7.1 ± 1.9 | 7.2 ± 2.0 |
| Sex (% Women) | ||
| Women | N=1228 (57.3%) | N=3063 (59.5%) |
| Men | N=917 (42.7%) | N=2082 (40.5%) |
| Race Ethnicity | ||
| African American / Black (not Hispanic) | N=401 (18.7%) | N=803 (15.6%) |
| American Indian / Native American / Alaskan Native | N=12 (0.6%) | N= 258 (5.0%) |
| Asian/Pacific Islander | N=13 (0.6%) | N=50 (1.0%) |
| White | N=1563 (73.0%) | N=3246 (63.3%) |
| Missing | N=0 (0.0%) | N=13 (0.3%) |
| Hispanic | N=107 (5.0%) | N=677 (13.2%) |
| Other/Mixed | N=45 (2.1%) | N=98 (1.9%) |
| History of Cardiovascular Disease n (%) | ||
| Yes** | N=329 (15.3%) | N=721 (14%) |
| No | N=1816 (84.7%) | N=4424 (86.0%) |
data presented as (mean ± standard deviation)
self report of myocardial infarction, stroke, transient ischemic event, percutaneous transluminal coronary angioplasty, or coronary artery bypass graft
All participants gave written informed consent approved by the local Institutional Review Boards prior to participation in this study. Participants completed initial eligibility assessments and provided baseline data prior to randomization, and these data are used for the analyses presented in this manuscript. These data include demographic characteristics [age, sex, race/ethnicity, cardiovascular disease history (self report of myocardial infarction, stroke, transient ischemic event, percutaneous transluminal coronary angioplasty, or coronary artery bypass graft), use of diabetes medication], physical activity assessed using accelerometry, physical activity assessed using self-report, and cardiorespiratory fitness according to a standardized protocol as described below.
Assessment of Physical Activity
Accelerometry
The RT3 triaxial accelerometer (StayHealthy®, Monrovia, CA, USA) was used to provide an objective measure of physical activity. Based on the recommendations from the manufacturer, participants were instructed to wear the device at a location consistent with the anatomical location of the anterior iliac spine with the accelerometer placed in a vertical position. The accelerometer was worn on the belt or waistband of the clothing; however, participants were also provided with a belt they could wear to secure the accelerometer to the proper location at the waist in the event that it could not be attached properly to their clothing. Participants were also provided written instructions that included the proper placement of the accelerometer on the body, specific dates (days) that the accelerometer should be worn, procedures to follow should there be difficulty with the operation of the accelerometer, and procedures for returning the accelerometer. The data collection mode for the accelerometer was set in the 3 axis and 1 minute epoch mode.
Participants were provided the accelerometer during a visit to the research center as part of an assessment visit, and they were requested to wear the accelerometer for the remainder of that day (partial day), 6 consecutive days following the visit (6 full days), and to wear it until it was returned to the clinic on the 7th day. Thus, the protocol allowed for up to 6 full days of data collection. Participants were instructed to wear the accelerometer during all waking hours over this period, and to only remove it during periods of bathing, showering, or other water-based activities. Quality control procedures were implemented, and if data were deemed to be invalid an attempt was made to have the subject wear the accelerometer for an additional period to provide valid data.
Data for a given day were considered valid if the accelerometer was worn for ≥10 hours on that day, which is consistent with previously published recommendations for the use of accelerometer to measure physical activity (9). The accelerometer was determined not to have been worn for periods defined as ≥20 continuous minutes of no activity counts on the accelerometer, and this was subtracted from 24 hours (1440 minutes) to determine if the ≥10 hour per day criterion was achieved so that a day could be considered a valid one. To be included in the analyses, a subject had to provide at least 4 valid days of accelerometry data.
Total energy expenditure per minute (kcal per minute) and estimated resting energy expenditure (kcal per minute) were provided by the StayHealthy® software which accompanied the RT3 accelerometer. Using these data, metabolic equivalents (METs) per minute were computed by dividing the estimated total energy expenditure per minute by the estimated resting energy expenditure [METs = total energy expenditure per minute ÷ estimated resting energy expenditure]. Physical activity periods that are consistent with public health recommendations were identified. The American College of Sports Medicine and the American Heart Association define moderate intensity physical activity as ≥3 METs per minute, and it has been recommended that bouts of activity be at ≥10 minutes in duration (6). Thus, accelerometry data were analyzed to identify periods that were consistent with these recommendations (≥3 METs per minute and ≥10 minutes in duration). Vigorous bouts of physical activity consistent with ≥6 METs per minute and ≥10 minutes in duration were also identified for analysis.
Self-Reported Leisure-Time Physical Activity (LTPA)
Within the Look AHEAD study LTPA was assessed on a sub-sample of approximately 50 percent of the participants at baseline, which reflects the same subject pool as those who completed measurements using accelerometry. Self-reported LTPA was assessed using the questionnaire developed for the Harvard Alumni Study (12) as part of a structured interview. LTPA was assessed by participants reporting their activity over the past week. Activities assessed included flights of stairs (10 steps = 1 flight), number of city blocks walked (1 mile = 12 blocks), and other sport, recreational, or fitness activities. Standardized scoring procedures were used to compute energy expenditure (kcal/wk) of LTPA (12). Participants also reported the number of days per week that they participated in LTPA that was of sufficient intensity to “engage in regular activity akin to brisk walking, jogging, bicycling, etc. long enough to work up a sweat, get your heart thumping, or get out of breath,” which will be referred to as “sweat episodes”.
Additional Baseline Assessments
A questionnaire was used to assess age, sex, ethnicity, current diabetes treatment, and history of cardiovascular disease. Previously described methods were used to measure height, weight, and BMI (8). A maximal graded exercise treadmill test was used to assess cardiorespiratory fitness at baseline as previously described (22). This test was terminated at the point of volitional exhaustion or at the point where ACSM (1) test termination criteria were observed. A baseline test was considered valid if the maximal heart rate was ≥85% of age-predicted maximal heart rate (HRMax = 220 minus age) if the participant was not taking a beta-adrenergic blocking medication (beta-blocker). If the participant was taking a beta blocking medicine, the baseline test was considered valid if Rate of Perceived Exertion (RPE) was ≥18 at the point of termination. Moreover, to be eligible for participation in the Look AHEAD Study the participant needed to achieve ≥4 METs on the baseline graded exercise test, where 1 MET is equal to 3.5 ml/kg/min of oxygen uptake.
Statistical Analysis
All analyses were performed using SAS version 9.1 (SAS Institute, Cary, NC). Statistical significance was defined as p≤0.05. Bivariate analyses were performed to examine differences in bouts per day meeting the criteria of ≥10 minutes per bout and either ≥3 METs per minute or ≥6 METs per minute within categories of BMI, sex, race/ethnicity, age, fitness, diabetes medication usage, and history of cardiovascular disease. For individuals found to have at least one bout of physical activity meeting the criteria of either ≥10 minutes per bout and ≥3 METs per minute or either ≥10 minutes per bout and ≥6 METs per minute, additional bivariate analyses were performed to test for differences in minutes per bout, METs per minute, and MET-minutes for all bouts meeting the criteria. Differences in self-reported LTPA (kcal/wk and sweat episodes per week) within categories of BMI, sex, race/ethnicity, age, fitness, diabetes medication usage, and history of cardiovascular disease were examined.
Multivariate analyses were performed using PROC GLM in SAS to determine the effect of age, BMI, sex, race/ethnicity, fitness, diabetes medication, and history of cardiovascular disease (self report of myocardial infarction, stroke, transient ischemic event, percutaneous transluminal coronary angioplasty, or coronary artery bypass graft) on objective measures of physical activity using accelerometry. Analyses were performed with bouts per day, minutes per bout, METs per minute, and MET-minutes considered as the dependent measures. Separate analyses were performed for these dependent measures for bouts of activity meeting the criteria of ≥10 minutes per bout and either ≥3 METs per bout or ≥6 METs per bout.
Results
Of the 5145 participants randomized into the Look AHEAD Study, 2,627 were at the 8 Look AHEAD clinical sites participating in the accelerometry sub-study. Of these participants, 2,240 (85.3% of the 2,627 participants) provided accelerometry data at baseline, with reasons for missing data including equipment failure, participant refusal, time/scheduling, and other reasons. Within the “other reasons” category, some clinics did not consider this portion of the Look AHEAD trial as part of the larger trial, and thus not all participants at these clinic sites were presented with an opportunity to consent and participate in the study, with this reason accounting for approximately 21% of the missing baseline accelerometry files. Visual inspection of individual data graphs were performed to determine the presence of activity energy expenditure as depicted by vertical lines over the course of the wear period, the presence of episodes of activity interspersed with sustained periods of zero activity indicating the unit was removed for sleeping, and weekly activity energy expenditure was within reasonable limits for this population (between 200 and 15,000 kcal). Using these criteria, 95.8% (2,145) of the data files available were valid and considered for analysis in this study. Baseline demographic data are presented in Table 1.
Separate analyses were performed using all days that achieved the minimum of ≥10 hours per day of wear time, along with the first 4 days, 5 days, or 6 days that achieved the minimum of ≥10 hours per day of wear time. The pattern of results did not change when data were analyzed using 4, 5, 6, or all days that met the ≥10 hours per day of wear time (data not shown), and therefore the following results are described using data from all days that met this criterion of ≥10 hours of wear time.
Comparison by BMI Categories
Participants were categorized based on baseline BMI as 25.0 to <27.0, 27.0 to <30.0, 30.0 to <35.0, 35.0 to <40.0, and ≥40 kg/m2 (see Tables 2 and 3). There was a significant difference between BMI categories for bouts per day achieving the ≥3 METs and ≥10 minute duration criteria, with fewer bouts identified in those with greater BMI. For participants who had a period meeting these criteria, the duration per bout was lower at higher BMI categories. A similar pattern was shown for METs per bout, MET-minutes for bouts meeting these criteria, and bouts of activity per day. Individuals at higher categories of BMI also had fewer bouts per day, shorter duration of activity bouts, and lower METs per bout, and lower MET-minutes when the criteria of ≥6 METs and ≥10 minutes was applied to the data.
Table 2.
Accelerometry determined physical activity for bouts ≥3 METs per minute for ≥10 minutes in duration by categories of BMI, sex, race/ethnicity, age, fitness, diabetes treatment, and cardiovascular disease history (mean ± standard deviation).
| Variable | Categories | Bouts per Day | Minutes per Bout* | METs per Minute* | Total MET-minutes* |
|---|---|---|---|---|---|
| BMI | 25.0 to <27.0 kg/m2 | 0.79 ± 1.21 (N=46) | 20.74 ± 10.29 (N=35) | 5.14 ± 1.11 (N=35) | 113.9 ± 87.09 (N=35) |
| 27.0 to <30.0 kg/m2 | 0.72 ± 0.79 (N=235) | 22.21 ± 10.81 (N=172) | 5.36 ± 1.16 (N=172) | 125.3 ± 81.98 (N=172) | |
| 30.0 to <35.0 kg/m2 | 0.65 ± 0.90 (N=719) | 21.09 ± 10.06 (N=522) | 5.25 ± 1.00 (N=521) | 115.1 ± 71.58 (N=521) | |
| 35.0 to <40.0 kg/m2 | 0.59 ± 0.78 (N=619) | 18.79 ± 9.05 (N=448) | 5.11 ± 1.02 (N=448) | 100.0 ± 67.42 (N=448) | |
| ≥40 kg/m2 | 0.52 ± 0.95 (N=525) | 17.02 ± 7.51 (N=346) | 4.95 ± 0.86 (N=346) | 86.46 ± 49.00 (N=346) | |
| p-value | 0.0146 | <.0001 | <.0001 | <.0001 | |
| Sex | Men | 0.83 ± 1.00 (N=917) | 20.65 ± 10.26 (N=729) | 5.17 ± 1.03 (N=728) | 111.7 ± 76.35 (N=728) |
| Women | 0.45 ± 0.73 (N=1228) | 18.63 ± 8.64 (N=795) | 5.13 ± 0.98 (N=795) | 99.34 ± 60.38 (N=795) | |
| p-value | <.0001 | <.0001 | 0.4246 | 0.0005 | |
| Race/Ethnicity | African American/Black | 0.45 ± 0.64 (N=401) | 17.94 ± 8.71 (N=264) | 5.08 ± 0.99 (N=263) | 94.77 ± 60.31 (N=263) |
| White | 0.65 ± 0.88 (N=1563) | 20.03 ± 9.58 (N=1129) | 5.17 ± 1.00 (N=1 129) | 107.7 ± 69.04 (N=1 129) | |
| Hispanic | 0.74 ± 1.39 (N=107) | 18.88 ± 10.11 (N=82) | 5.18 ± 1.16 (N=82) | 104.9 ± 88.25 (N=82) | |
| Other/Mixed/Missing | 0.55 ± 0.87 (N=74) | 19.78 ± 9.98 (N=49) | 5.14 ± 0.87 (N=49) | 104.7 ± 63.75 (N=49) | |
| p-value | 0.0002 | 0.0121 | 0.6391 | 0.0557 | |
| Age | <50 years | 0.60 ± 0.94 (N=208) | 19.08 ± 8.34 (N=150) | 5.23 ± 1.00 (N=150) | 104.2 ± 64.58 (N=150) |
| 50 to <60 years | 0.60 ± 0.85 (N=964) | 19.60 ± 9.82 (N=695) | 5.21 ± 1.05 (N=694) | 106.9 ± 73.88 (N=694) | |
| 60 to <70 years | 0.64 ± 0.92 (N=811) | 19.77 ± 9.52 (N=574) | 5.09 ± 0.96 (N=574) | 104.6 ± 65.13 (N=574) | |
| ≥70 years | 0.52 ± 0.70 (N=162) | 19.40 ± 8.91 (N=105) | 4.95 ± 0.89 (N=105) | 99.40 ± 58.09 (N=105) | |
| p-value | 0.4202 | 0.8766 | 0.0223 | 0.7435 | |
| Fitness | <6 METs | 0.44 ± 0.85 (N=645) | 16.55 ± 7.51 (N=382) | 4.67 ± 0.65 (N=382) | 78.73 ± 42.87 (N=382) |
| 6 to <8 METs | 0.57 ± 0.73 (N=881) | 19.25 ± 8.87 (N=635) | 5.16 ± 0.93 (N=635) | 102.4 ± 61.02 (N=635) | |
| 8 to <10 METs | 0.79 ± 1.07 (N=435) | 21.44 ± 10.18 (N=347) | 5.39 ± 1.05 (N=346) | 119.9 ± 72.42 (N=346) | |
| ≥10 METs | 1.02 ± 0.91 (N=181) | 24.29 ± 11.74 (N=160) | 5.75 ± 1.34 (N=160) | 148.1 ± 102.8 (N=160) | |
| p-value | <.0001 | <.0001 | <.0001 | <.0001 | |
| Diabetes Medication | No Glucose Lowering Medication | 0.64 ± 0.89 (N=267) | 20.02 ± 9.57 (N=197) | 5.19 ± 1.05 (N=197) | 108.0 ± 65.55 (N=197) |
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 0.61 ± 0.89 (N=967) | 19.81 ± 9.60 (N=688) | 5.19 ± 0.98 (N=687) | 107.4 ± 68.48 (N=687) | |
| Thiazolidinedione | 0.59 ± 0.75 (N=482) | 19.77 ± 9.58 (N=342) | 5.09 ± 1.04 (N=342) | 105.1 ± 72.68 (N=342) | |
| Insulin Alone | 0.55 ± 0.71 (N=86) | 20.13 ± 10.31 (N=56) | 5.07 ± 1.02 (N=56) | 106.8 ± 70.93 (N=56) | |
| Insulin plus glucose lowering medication (Not including thiazolidinedione) | 0.63 ± 0.86 (N=153) | 18.28 ± 8.24 (N=1 12) | 5.00 ± 0.88 (N=1 12) | 93.50 ± 51.54 (N=112) | |
| Insulin plus thiazolidinedione | 0.68 ± 1.23 (N=157) | 18.28 ± 9.64 (N=111) | 5.21 ± 1.03 (N=111) | 100.5 ± 79.85 (N=111) | |
| p-value | 0.8631 | 0.3827 | 0.2949 | 0.4437 | |
| Cardiovascular Disease History | No | 0.61 ± 0.99 (N=329) | 19.11 ± 9.29 (N=226) | 5.03 ± 0.98 (N=226) | 99.70 ± 67.85 (N=226) |
| Yes | 0.61 ± 0.85 (N=1816) | 19.68 ± 9.54 (N=1298) | 5.17 ± 1.01 (N=1297) | 106.2 ± 68.87 (N=1297) | |
| p-value | 0.9854 | 0.4001 | 0.0463 | 0.1903 |
Indicates that data represent participants who reported ≥1 bout during the observation period that met the criteria of ≥3 METs per minute and ≥10 minutes for that bout.
Table 3.
Accelerometry determined physical activity for bouts ≥6 METs per minute for ≥10 minutes in duration by categories of BMI, sex, race/ethnicity, age, fitness, diabetes treatment, and cardiovascular disease history (mean ± standard deviation).
| Variable | Categories | Bouts per Day | Minutes per Bout* | METs per Minute* | MET-minutes* |
|---|---|---|---|---|---|
| BMI | 25.0 to <27.0 kg/m2 | 0.13 ± 0.34 (N=46) | 18.77 ± 7.83 (N=12) | 8.34 ± 1.61 (N=12) | 158.3 ± 82.38 (N=12) |
| 27.0 to <30.0 kg/m2 | 0.18 ± 0.35 (N=235) | 20.09 ± 9.88 (N=73) | 8.06 ± 1.24 (N=73) | 165.3 ± 94.85 (N=73) | |
| 30.0 to <35.0 kg/m2 | 0.15 ± 0.39 (N=719) | 19.49 ± 9.85 (N=217) | 8.03 ± 1.20 (N=217) | 159.7 ± 93.99 (N=217) | |
| 35.0 to <40.0 kg/m2 | 0.11 ± 0.28 (N=619) | 18.01 ± 7.97 (N=158) | 7.72 ± 0.99 (N=158) | 140.8 ± 74.29 (N=158) | |
| ≥40 kg/m2 | 0.06 ± 0.17 (N=525) | 17.08 ± 6.98 (N=97) | 7.36 ± 0.92 (N=97) | 127.7 ± 64.50 (N=97) | |
| p-value | <.0001 | 0.1051 | <.0001 | 0.0075 | |
| Sex | Men | 0.16 ± 0.35 (N=917) | 18.61 ± 8.71 (N=301) | 8.05 ± 1.18 (N=301) | 152.6 ± 84.02 (N=301) |
| Women | 0.09 ± 0.28 (N=1228) | 18.83 ± 9.11 (N=256) | 7.58 ± 1.04 (N=256) | 145.8 ± 85.68 (N=256) | |
| p-value | <.0001 | 0.7652 | <.0001 | 0.3443 | |
| Race/Ethnicity | African American/Black | 0.07 ± 0.17 (N=401) | 20.66 ± 10.03 (N=74) | 7.65 ± 1.01 (N=74) | 160.3 ± 89.73 (N=74) |
| White | 0.13 ± 0.31 (N=1563) | 18.29 ± 8.45 (N=433) | 7.85 ± 1.16 (N=433) | 146.5 ± 81.35 (N=433) | |
| Hispanic | 0.19 ± 0.63 (N=107) | 20.19 ± 11.48 (N=34) | 7.88 ± 1.09 (N=34) | 164.9 ± 117.7 (N=34) | |
| Other/Mixed/Missing | 0.12 ± 0.25 (N=74) | 18.07 ± 7.97 (N=16) | 8.13 ± 1.22 (N=16) | 146.9 ± 69.13 (N=16) | |
| p-value | 0.0005 | 0.1334 | 0.3776 | 0.4133 | |
| Age | <50 years | 0.10 ± 0.20 (N=208) | 20.52 ± 11.21 (N=62) | 8.00 ± 1.34 (N=62) | 168.1 ± 111.5 (N=62) |
| 50 to <60 years | 0.12 ± 0.32 (N=964) | 19.42 ± 8.60 (N=253) | 7.89 ± 1.18 (N=253) | 156.0 ± 82.88 (N=253) | |
| 60 to <70 years | 0.13 ± 0.34 (N=811) | 17.41 ± 8.35 (N=212) | 7.75 ± 1.03 (N=212) | 137.3 ± 77.29 (N=212) | |
| ≥70 years | 0.08 ± 0.23 (N=162) | 18.20 ± 8.75 (N=30) | 7.60 ± 1.11 (N=30) | 141.3 ± 78.77 (N=30) | |
| p-value | 0.2060 | 0.0320 | 0.2190 | 0.0267 | |
| Fitness | <6 METs | 0.03 ± 0.13 (N=645) | 15.69 ± 5.92 (N=64) | 6.58 ± 0.32 (N=64) | 103.4 ± 40.02 (N=64) |
| 6 to <8 METs | 0.11 ± 0.25 (N=881) | 17.18 ± 6.79 (N=232) | 7.61 ± 0.66 (N=232) | 131.9 ± 57.38 (N=232) | |
| 8 to <10 METs | 0.20 ± 0.46 (N=435) | 19.09 ± 9.46 (N=165) | 8.18 ± 1.20 (N=165) | 158.8 ± 92.70 (N=165) | |
| ≥10 METs | 0.30 ± 0.47 (N=181) | 23.78 ± 11.59 (N=96) | 8.61 ± 1.43 (N=96) | 206.5 ± 111.9 (N=96) | |
| p-value | <.0001 | <.0001 | <.0001 | <.0001 | |
| Diabetes Medication | No Glucose Lowering Medication | 0.15 ± 0.32 (N=267) | 17.79 ± 6.44 (N=78) | 7.75 ± 1.07 (N=78) | 139.1 ± 56.10 (N=78) |
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 0.13 ± 0.36 (N=967) | 18.99 ± 8.76 (N=256) | 7.89 ± 1.19 (N=256) | 152.9 ± 84.81 (N=256) | |
| Thiazolidinedione | 0.10 ± 0.26 (N=482) | 18.85 ± 10.54 (N=126) | 7.82 ± 1.10 (N=126) | 151.4 ± 99.30 (N=126) | |
| Insulin Alone | 0.13 ± 0.29 (N=86) | 18.48 ± 8.84 (N=21) | 7.71 ± 1.24 (N=21) | 145.1 ± 83.28 (N=21) | |
| Insulin plus glucose lowering medication (Not including thiazolidinedione) | 0.09 ± 0.22 (N=153) | 18.64 ± 8.36 (N=31) | 7.76 ± 0.97 (N=31) | 145.2 ± 72.21 (N=31) | |
| Insulin plus thiazolidinedione | 0.09 ± 0.22 (N=157) | 17.91 ± 8.70 (N=40) | 7.75 ± 1.21 (N=40) | 142.3 ± 93.78 (N=40) | |
| p-value | 0.1566 | 0.9196 | 0.9027 | 0.8412 | |
| Cardiovascular Disease History | No | 0.11 ± 0.30 (N=329) | 17.51 ± 8.08 (N=75) | 7.70 ± 1.02 (N=75) | 138.3 ± 82.72 (N=75) |
| Yes | 0.12 ± 0.31 (N=1816) | 18.90 ± 9.00 (N=482) | 7.86 ± 1.16 (N=482) | 151.2 ± 85.04 (N=482) | |
| p-value | 0.4194 | 0.2087 | 0.2734 | 0.2189 |
Indicates that data represent participants who reported ≥1 bout during the observation period that met the criteria of ≥6 METs per minute and ≥10 minutes for that bout.
Comparison by Sex
There were significantly more bouts per day in men than in women when using the ≥3 METs and ≥10 minute duration criteria (0.83±1.00 vs. 0.45±0.73 bouts per day) (p<0.0001) (see Table 2). Moreover, for bouts identified that met these criteria, duration per bout was significantly longer for men (20.65±10.26 minutes) than women (18.63±8.64 minutes) (p<0.0001). METs per minute for these bouts did not differ by sex; however, total MET-minutes for all bouts meeting the criteria of ≥3 METs and ≥10 minute duration was higher in men than women (p=0.0005).
When the criteria of ≥6 METs and ≥10 minutes were applied to the data, men continued to have more activity bouts that met these criteria than women (0.16±0.35 vs. 0.09±0.28 bouts per day) (p<0.0001) (see Table 3). The duration per bout did not differ between sexes (18.61±8.71 vs. 18.83±9.11 minutes), but METs per minute was greater for men (8.05±1.18 METs) compared to women (7.58±1.04 METs) (p<0.0001). However, total MET-minutes for all bouts meeting the criteria of ≥3 METs and ≥10 minute duration did not differ by sex.
Comparison by Ethnic/Racial Group
There was a significant effect of ethnic/racial group on bouts per day and minutes per bout when using the criteria of ≥3 METs with ≥10 minute duration, with individuals identified as African American/Black having the fewest bouts per day and the lowest minutes per bout (see Table 2). African American/Black individuals also had the fewest bouts per day when the criteria of ≥6 METs with ≥10 minute duration was applied to the data (see Table 3). However, there was no significant effect of ethnicity/race for duration per bout, METs per minute, or total MET-minutes using either of these criteria.
Comparison by Age
There was no significant difference between age categories for bouts per day of participating in activity ≥10 minutes in duration when defined using either the ≥3 METs or ≥6 METs categories. However, METs per minute decreased with advancing age for ≥3 METs activities, whereas minutes per bout and total MET-minutes decreased with advancing age for ≥6 METs activities (see Tables 2 and 3).
Comparison by Baseline Fitness
Bouts per day for both ≥3 and ≥6 METs were positively associated with fitness. For individuals reporting participation in bouts that were ≥3 or ≥6 METs that were ≥10 minutes in duration, there was a significant increase in duration per bout, METs per minute, and total MET-minutes of physical activity meeting these criteria with increasing levels of fitness (see Tables 2 and 3).
Comparison by Type of Diabetes Treatment and by History of Cardiovascular Disease
There was no significant associate between type of diabetes medication and bouts per day, duration per bout, METs per minute, or total MET-minutes for either the ≥3 METs or ≥6 METs physical activity categories. When grouped according to history of cardiovascular disease, individuals who had a history of cardiovascular disease and participated in activity bouts of ≥3 METs that were of at least 10 minutes in duration had higher METs per minute (5.17±1.01 METs) than did those without a history of cardiovascular disease (5.03±0.98 METs)(p=0.0463). Data are presented in Tables 2 and 3.
Self-Reported Leisure-Time Physical Activity (LTPA)
Self reported LTPA was compared across categories of BMI, sex, race, age, fitness, diabetes medication usage, and history of cardiovascular disease (see Table 4). Energy expenditure in LTPA was negatively associated with BMI, was greater in men than women, was lowest in individuals classified as African-American/Black, and was positively associated with fitness. There was no effect of age, type of diabetes medication usage, or history of cardiovascular disease on energy expenditure in self-reported LTPA. A similar pattern of results was observed when data were analyzed for “sweat episodes per week.”
Table 4.
Self-reported leisure-time physical activity (LTPA) by categories of BMI, sex, race/ethnicity, age, fitness, diabetes treatment, and cardiovascular disease history.
| Variable | Categories | Energy Expenditure (kcal/wk) Median (25th, 75th Percentiles) N | Sweat Episodes per Week Median (25th, 75th Percentiles) N |
|---|---|---|---|
| BMI | 25.0 to <27.0 kg/m2 | 686.0 (224.0, 1515) N=46 | 1.0 (0.0, 3.0) N=46 |
| 27.0 to <30.0 kg/m2 | 644.0 (168.0, 1500) N=235 | 1.0 (0.0, 4.0) N=234 | |
| 30.0 to <35.0 kg/m2 | 640.5 (168.0, 1417) N=716 | 1.0 (0.0, 3.0) N=714 | |
| 35.0 to <40.0 kg/m2 | 514.8 (112.0, 1064) N=616 | 1.0 (0.0, 3.0) N=615 | |
| ≥40 kg/m2 | 280.0 (56.0, 784.0) N=522 | 0.0 (0.0, 2.5) N=520 | |
| p-value | <.0001 | <.0001 | |
| Sex | Men | 672.0 (196.0, 1490) N=911 | 1.0 (0.0, 3.0) N=907 |
| Women | 392.0 (100.0, 944.0) N=1225 | 0.0 (0.0, 3.0) N=1223 | |
| p-value | <.0001 | <.0001 | |
| Race/Ethnicity | African American/Black | 392.0 (100.0, 840.0) N=401 | 0.0 (0.0, 3.0) N=400 |
| White | 532.0 (140.0, 1316) N=1554 | 1.0 (0.0, 3.0) N=1550 | |
| Hispanic | 392.0 (84.0, 1316) N=107 | 1.0 (0.0, 3.0) N=106 | |
| Other/Mixed/Missing | 640.5 (112.0, 1200) N=74 | 0.0 (0.0, 3.0) N=74 | |
| p-value | 0.0004 | 0.0919 | |
| Age | <50 years | 524.0 (112.0, 1008) N=207 | 1.0 (0.0, 3.0) N=207 |
| 50 to <60 years | 504.0 (140.0, 1224) N=960 | 1.0 (0.0, 3.0) N=958 | |
| 60 to <70 years | 468.0 (112.0, 1200) N=807 | 1.0 (0.0, 3.0) N=803 | |
| ≥70 years | 528.5 (112.0, 1359) N=162 | 0.0 (0.0, 3.0) N=162 | |
| p-value | 0.7388 | 0.6926 | |
| Fitness | <6 METs | 226.0 (56.0, 747.5) N=644 | 0.0 (0.0, 2.0) N=642 |
| 6 to <9 METs | 505.5 (140.0, 1064) N=875 | 1.0 (0.0, 3.0) N=874 | |
| 8 to <10 METs | 728.0 (196.0, 1515) N=435 | 1.0 (0.0, 3.0) N=433 | |
| ≥10 METs | 1310 (560.0, 2263) N=180 | 3.0 (0.0, 4.0) N=179 | |
| p-value | <.0001 | <.0001 | |
| Diabetes Medication | No Glucose Lowering Medication | 616.0 (168.0, 1304) N=267 | 1.0 (0.0, 4.0) N=267 |
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 476.0 (112.0, 1205) N=964 | 1.0 (0.0, 3.0) N=960 | |
| Thiazolidinedione | 449.0 (112.0, 1132) N=478 | 1.0 (0.0, 3.0) N=478 | |
| Insulin Alone | 434.5 (140.0, 1008) N=86 | 1.0 (0.0, 3.0) N=86 | |
| Insulin plus glucose lowering medication (Not including thiazolidinedione) | 426.0 (112.0, 1023) N=152 | 1.0 (0.0, 3.0) N=150 | |
| Insulin plus thiazolidinedione | 561.0 (112.0, 1393) N=156 | 0.0 (0.0, 3.0) N=156 | |
| p-value | 0.1434 | 0.3277 | |
| Cardiovascular Disease History | No | 477.0 (112.0, 1182) N=1808 | 1.0 (0.0, 3.0) N=1804 |
| Yes | 479.0 (112.0, 1344) N=328 | 1.0 (0.0, 3.0) N=326 | |
| p-value | 0.9086 | 0.1849 |
Multivariate Analysis
Results of the multivariate models using the criteria of ≥10 minutes in duration and ≥3 METs to examine components of physical activity are shown in Table 5. Bouts per day were significantly higher in men than women, and positively associated with fitness (p<0.0001). Minutes per bout were significantly higher with increasing levels of fitness (p=<0.0001), with a trend for fewer minutes per bout with increasing BMI (p=0.0572). METs per minute were significantly higher in women than men (p=0.0001) and positively associated with fitness (p<0.0001), with a trend observed for increasing METs per minute with BMI (p<0.0982). However, total MET-minutes for bouts meeting the criteria of ≥10 minutes in duration and ≥3 METs were positively associated with fitness (p<0.0001), with a trend for a positive association between total MET-minutes for bouts meeting the criteria and age (p=0.0821).
Table 5.
Multivariate model based on accelerometry data for bouts defined as ≥3 METs per minute for a duration of ≥10 minutes.
| Model | Estimate | Standard Error | F-Value | P-value | R2 for Model |
|---|---|---|---|---|---|
| Dependent Variable: Bouts per Day | 0.0732 | ||||
| Age | 0.0001 | 0.0032 | 0.00 | 0.9688 | |
| BMI | 0.0006 | 0.0037 | 0.03 | 0.8690 | |
| Sex (Women versus Men) | −0.2999 | 0.0424 | 50.12 | <0.0001 | |
| Race/Ethnicity (White is the reference group) | 2.42 | 0.0644 | |||
| African-American/Black | −0.1075 | 0.0491 | |||
| Hispanic | 0.1033 | 0.0865 | |||
| Other/Mixed/Missing | −0.0702 | 0.1028 | |||
| Baseline Fitness (maximal METs) | 0.0696 | 0.0128 | 29.77 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.45 | 0.8108 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | −0.0138 | 0.0592 | |||
| Thiazolidinedione | −0.0274 | 0.0656 | |||
| Insulin Alone | −0.0075 | 0.1063 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | 0.0465 | 0.0872 | |||
| Insulin + Thiazolidinedione | 0.0725 | 0.0871 | |||
| Without Baseline history of CVD | 0.0511 | 0.0539 | 0.90 | 0.3425 | |
| Dependent Variable: Minutes per Bout * | 0.0814 | ||||
| Age | 0.0693 | 0.0406 | 2.91 | 0.0883 | |
| BMI | −0.0922 | 0.0485 | 3.62 | 0.0572 | |
| Sex (Women versus Men) | −0.2286 | 0.5368 | 0.18 | 0.6703 | |
| Race/Ethnicity (White is the reference group) | 1.88 | 0.1313 | |||
| African-American/Black | −1.4866 | 0.6439 | |||
| Hispanic | −0.8860 | 1.0659 | |||
| Other/Mixed/Missing | −0.4300 | 1.3418 | |||
| Baseline Fitness (maximal METs) | 0.8991 | 0.1617 | 53.69 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.52 | 0.7594 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 0.1964 | 0.7466 | |||
| Thiazolidinedione | 0.6639 | 0.8297 | |||
| Insulin Alone | 1.4732 | 1.3991 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | −0.4743 | 1.0970 | |||
| Insulin + Thiazolidinedione | 0.0157 | 1.1096 | |||
| Without Baseline history of CVD | 0.4176 | 0.6987 | 0.36 | 0.5501 | |
| Dependent Variable: METs per Minute * | 0.1325 | ||||
| Age | 0.0047 | 0.0042 | 1.27 | 0.2602 | |
| BMI | 0.0082 | 0.0050 | 2.74 | 0.0982 | |
| Sex (Women versus Men) | 0.2109 | 0.0550 | 14.69 | 0.0001 | |
| Race/Ethnicity (White is the reference group) | 0.39 | 0.7591 | |||
| African-American/Black | −0.0636 | 0.0661 | |||
| Hispanic | −0.0574 | 0.1092 | |||
| Other/Mixed/Missing | −0.0537 | 0.1375 | |||
| Baseline Fitness (maximal METs) | 0.2105 | 0.0164 | 164.77 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 1.37 | 0.2315 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 0.0650 | 0.0765 | |||
| Thiazolidinedione | 0.0044 | 0.0850 | |||
| Insulin Alone | 0.0476 | 0.1433 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | −0.0460 | 0.1124 | |||
| Insulin + Thiazolidinedione | 0.2341 | 0.1137 | |||
| Without Baseline history of CVD | −0.0075 | 0.0716 | 0.01 | 0.9171 | |
| Dependent Variable: MET-minutes * | 0.1095 | ||||
| Age | 0.5042 | 0.2898 | 3.03 | 0.0821 | |
| BMI | −0.3135 | 0.3455 | 0.82 | 0.3644 | |
| Sex (Women versus Men) | 3.5176 | 3.8293 | 0.84 | 0.3585 | |
| Race/Ethnicity (White is the reference group) | 1.29 | 0.2778 | |||
| African-American/Black | −8.9192 | 4.5984 | |||
| Hispanic | −2.7792 | 7.5975 | |||
| Other/Mixed/Missing | −4.4441 | 9.5646 | |||
| Baseline Fitness (maximal METs) | 101.45 | <0.0001 | |||
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.62 | 0.6836 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 3.1416 | 5.3222 | |||
| Thiazolidinedione | 4.6801 | 5.9138 | |||
| Insulin Alone | 10.4050 | 9.9725 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | −4.1663 | 7.8196 | |||
| Insulin + Thiazolidinedione | 7.1660 | 7.9090 | |||
| Without Baseline history of CVD | 2.0723 | 4.9807 | 0.17 | 0.6774 |
Indicates that data represent participants who reported ≥1 bout during the observation period that met the criteria of ≥3 METs per minute and ≥10 minutes for that bout.
Results of the multivariate models using the criteria of ≥10 minutes in duration and ≥6 METs to examine components of physical activity are shown in Table 6. Bouts per day was positively associated with age (p=0.0099) and fitness (p<0.0001), and was influenced by race/ethnicity with African-American/Black and Other/Mixed/Missing having lower values that Whites. Minutes per bout were significantly higher with increasing levels of fitness (p≤0.0001). METs per minute was negatively associated with BMI (p=0.0327), was lower in women than men (p=0.006) and was positively associated with fitness (p<0.0001), with a trend observed for increasing METs per minute with BMI (p<0.0982). However, total MET-minutes for bouts meeting the criteria of ≥10 minutes in duration and ≥3 METs was positively associated with fitness (p<0.0001).
Table 6.
Multivariate model based on accelerometry data for bouts defined as ≥6 METs per minute for a duration of ≥10 minutes.
| Model | Estimate | Standard Error | F-Value | P-value | R-Square for Model |
|---|---|---|---|---|---|
| Dependent Variable: Bouts per Day | 0.0807 | ||||
| Age | 0.0029 | 0.0011 | 6.67 | 0.0099 | |
| BMI | 0.0009 | 0.0013 | 0.48 | 0.4881 | |
| Sex (Women versus Men) | −0.0090 | 0.0151 | 0.36 | 0.5501 | |
| Race/Ethnicity (White is the reference group) | 3.27 | 0.0204 | |||
| African-American/Black | −0.0399 | 0.0174 | |||
| Hispanic | 0.0562 | 0.0307 | |||
| Other/Mixed/Missing | −0.0138 | 0.0365 | |||
| Baseline Fitness (maximal METs) | 0.0455 | 0.0045 | 100.85 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.72 | 0.6062 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | −0.0030 | 0.0210 | |||
| Thiazolidinedione | −0.0254 | 0.0233 | |||
| Insulin Alone | 0.0247 | 0.0378 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | −0.0266 | 0.0310 | |||
| Insulin + Thiazolidinedione | −0.0148 | 0.0309 | |||
| Without Baseline history of CVD | 0.0074 | 0.0191 | 0.15 | 0.6993 | |
| Dependent Variable: Minutes per Bout * | 0.0985 | ||||
| Age | −0.0751 | 0.0626 | 1.44 | 0.2306 | |
| BMI | −0.0223 | 0.0801 | 0.08 | 0.7805 | |
| Sex (Women versus Men) | 0.8540 | 0.8304 | 1.06 | 0.3042 | |
| Race/Ethnicity (White is the reference group) | 1.54 | 0.2038 | |||
| African-American/Black | 2.1024 | 1.0996 | |||
| Hispanic | 1.8014 | 1.5373 | |||
| Other/Mixed/Missing | −0.0441 | 2.1904 | |||
| Baseline Fitness (maximal METs) | 1.2454 | 0.2310 | 29.06 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.33 | 0.8929 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 1.3583 | 1.1174 | |||
| Thiazolidinedione | 1.3329 | 1.2465 | |||
| Insulin Alone | 1.6337 | 2.1046 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | 1.1841 | 1.8220 | |||
| Insulin + Thiazolidinedione | 1.3074 | 1.6948 | |||
| Without Baseline history of CVD | 0.3069 | 1.1297 | 0.07 | 0.7860 | |
| Dependent Variable: METs per Minute * | 0.2538 | ||||
| Age | −0.0093 | 0.0073 | 1.62 | 0.2093 | |
| BMI | −0.0201 | 0.0094 | 4.58 | 0.0327 | |
| Sex (Women versus Men) | −0.2684 | 0.0972 | 7.62 | 0.0060 | |
| Race/Ethnicity (White is the reference group) | 0.82 | 0.4853 | |||
| African-American/Black | −0.1302 | 0.1287 | |||
| Hispanic | 0.0929 | 0.1800 | |||
| Other/Mixed/Missing | 0.2488 | 0.2565 | |||
| Baseline Fitness (maximal METs) | 0.2319 | 0.0270 | 73.48 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.23 | 0.9498 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 0.0993 | 0.1308 | |||
| Thiazolidinedione | 0.0542 | 0.1459 | |||
| Insulin Alone | 0.1068 | 0.2464 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | 0.1143 | 0.2133 | |||
| Insulin + Thiazolidinedione | 0.1854 | 0.1984 | |||
| Without Baseline history of CVD | 0.0726 | 0.1323 | 0.30 | 0.5832 | |
| Dependent Variable: MET-minutes * | 0.1462 | ||||
| Age | −0.7787 | 0.5823 | 1.79 | 0.1817 | |
| BMI | −0.4582 | 0.7447 | 0.38 | 0.5386 | |
| Sex (Women versus Men) | 3.1983 | 7.246 | 0.17 | 0.6790 | |
| Race/Ethnicity (White is the reference group) | 0.94 | 0.4233 | |||
| African-American/Black | 12.5487 | 10.2294 | |||
| Hispanic | 18.1756 | 14.3007 | |||
| Other/Mixed/Missing | 1.7140 | 20.3772 | |||
| Baseline Fitness (maximal METs) | 14.8832 | 2.1492 | 47.95 | <0.0001 | |
| Diabetes Medication (No Glucose Lowering Medication is the Reference Group) | 0.45 | 0.8144 | |||
| Glucose Lowering Medication (Not including insulin or thiazolidinedione) | 14.3984 | 10.3947 | |||
| Thiazolidinedione | 14.3224 | 11.5961 | |||
| Insulin Alone | 16.3091 | 19.5786 | |||
| Insulin + Glucose Lowering Medication (Not including thiazolidinedione) | 10.5168 | 16.9496 | |||
| Insulin + Thiazolidinedione | 16.4032 | 15.7665 | |||
| Without Baseline history of CVD | 1.9710 | 10.5095 | 0.04 | 0.8513 |
Indicates that data represent participants who reported ≥1 bout during the observation period that met the criteria of ≥6 METs per minute and ≥10 minutes for that bout.
DISCUSSION
The most recent physical activity guidelines for Americans has recommended at least 150 minutes per week of moderate intensity activity that is spread throughout the week (20). Adults with type 2 diabetes in the Look AHEAD Study are participating in <1 bout per day of physical activity that meet the criteria of ≥3 METs and ≥10 minutes in duration based on accelerometry data (see Table 2), <0.20 bouts per day of vigorous activity (≥6 METs) (see Table 3), and approximately ≤2 sweat episodes per week based on self-reported LTPA (see Table 4). Based on accelerometry, results showed that 71% of subjects had at least 1 activity bout that met the ≥3 METs and ≥10 minutes in duration criteria, with 26% meeting the ≥6 METs and ≥10 minutes in duration For those engaged in at least one activity bout per week that meet either the moderate-to-vigorous or vigorous intensity criteria for at least 10 consecutive minutes, the duration of these bouts of activity was approximately 15 to 20 minutes (see Tables 2 and 3), suggesting that few individuals were achieving the recommended level of physical activity. Moreover, 51% of subjects reported at least 1 sweat episode per week based on self-report in this study. Nwasuruba et al. (11) reported that between 23% and 37% of adults with type 2 diabetes were meeting the recommended level of physical activity based on 2003 Behavioral Risk Factor Surveillance Survey (BRFSS) data. Thus, there appears to be a need for interventions to increase the frequency and duration of sufficient doses of physical activity in individuals with type 2 diabetes to meet the recommended physical activity guidelines for adults, and this may improve diabetes control and minimize the risk of health complications or mortality related to this condition.
The data presented in this manuscript include objectively measured physical activity using accelerometry, which also provides information of the patterns of physical activity in individuals with type 2 diabetes enrolled in the Look AHEAD Study. We conducted extensive electronic library searches to identify other studies of individuals with type 2 diabetes that have used objective measures of physical activity and found few such studies. Samuel-Hodge et al. (15) used a uniaxial accelerometer to assess baseline levels of physical activity in an intervention study and reported on the minutes per day of light, moderate, and vigorous activity. However, this provides limited information on the pattern of activity that is moderate-to-vigorous in intensity that also meets the minimum recommended duration of 10 minutes as recommended by Haskell et al. (6) and the recent Physical Activity Guidelines for Americans (20). Thus, baseline data presented here from the Look AHEAD Study define activity based on the ability of a bout to meet the ≥10 minute duration while also meeting moderate-to-vigorous or vigorous intensity criteria. This may provide a clearer perspective of the patterns of physical activity in individuals with type 2 diabetes that meet the criteria for physical activity bouts that are recommended by leading health organizations compared with other studies that have examined physical activity in individuals with type 2 diabetes.
Despite the advantages of using objective monitoring, the use of accelerometry is not without limitations. For example, studies have regularly demonstrated that accelerometry appears to be best suited to provide valid and reliable data for activities that have a movement pattern similar to level walking and jogging (7). Moreover, while the use of activity counts have been used to define moderate and vigorous levels of physical activity, the activity counts vary by type of accelerometer and mode of activity. For example, the activity count thresholds for moderate and vigorous physical activity differ for the RT3 accelerometer (13) compared to other accelerometers (4, 17). Rowlands et al. (13) also reported that activity count thresholds for men when treadmill walking were 400 counts less than the activity count thresholds representing a variety of moderate-to-vigorous activities. Moreover, there are no published activity count thresholds for the RT3 accelerometer to define moderate or vigorous activity in overweight and obese older adults with type 2 diabetes, which is the population group examined in this study. The activity count thresholds to define moderate and vigorous physical activity reported by Rowlands et al. (13) were developed based on 19 boys with a mean age of 9.5±0.8 years and 15 men with a mean age of 20.7±1.4 years. Therefore, we computed METs from the total energy expenditure and resting energy expenditure data as defined earlier to identify periods which met ≥3 or ≥6 METs, which are the criteria for moderate and vigorous levels of physical activity.
Based on data from the 2003 BRFSS, African-American/Black adults with type 2 diabetes were less likely than White adults to engage in sufficient physical activity to meet the recommendation of at least 30 minutes per day of moderate intensity activity on 5 or more days per week or 20 minutes per day of vigorous activity on 3 or more days per week (11). Based on bivariate analyses presented for moderate-to-vigorous intensity physical activity, defined as ≥3 METs and ≥10 minutes in duration, it appears that African-Americans/Blacks participate in fewer bouts per day and fewer minutes per bout than Whites with type 2 diabetes, and this may contribute to lower total MET-minutes of physical activity (see Table 2). For vigorous physical activity (≥3 METs and ≥10 minutes in duration), this study showed that African-Americans/Blacks participants engaged in the fewest bouts of this level of physical activity (see Table 3). The multivariate model appears to confirm a race/ethnicity effect for bouts per day of either moderate-to-vigorous (≥3 METs) or vigorous (≥6 METs) intensity physical activity, with African-Americans/Blacks participating in fewer bouts per day of activity when compared with Whites (see Tables 5 and 6). A similar pattern was observed when examining self-reported LTPA (see Table 4). Thus, while all individuals with type 2 diabetes should be encouraged to participate in physical activity as part of their comprehensive treatment plan, particular attention may need to be given to interventions that target African-American/Black and other racial/ethnic groups that appear to have lower levels of physical activity.
The importance of understanding patterns of physical activity in this population is highlighted by the growing evidence that physical activity may be important for reducing mortality due to cardiovascular disease or all-causes in persons with type 2 diabetes. The review by Caspersen and Fulton (2) of studies examining the effect of walking on all-cause and cardiovascular disease mortality concluded that the reduction in risk ranged from 40% to 55%. Specifically, Gregg et al. (5) reported that the relative risk of all-cause mortality was 0.61 and 0.46 with 2.0–2.9 hrs/wk and 3.0–3.9 hrs/wk of walking compared to 0 hrs/wk, respectively. The risk of cardiovascular disease was reduced by 53% with 3.0–3.9 hrs/wk of walking. Tanasescu et al. (18) also reported a significant reduction in the risk of all-cause mortality of 40% with >5.3 hrs/wk of walking in adults with type 2 diabetes. Smith et al. (16) also reported hazard ratios of 0.54 and 0.19 for all-cause and cardiovascular disease mortality, respectively, for adults with diabetes who walked ≥1 mile per day compared with those who did not walk. While these data consistently show the beneficial effect of physical activity on reduction in mortality in individuals with type 2 diabetes, these data are based on self-report and provide little information on the patterns of physical activity. Understanding the patterns of physical activity may inform interventions that target increases in physical activity in patients with type 2 diabetes.
Church et al. (3) reported on the importance of fitness to reduce cardiovascular disease mortality in adults with type 2 diabetes. There was 1.2 hazard ratio for cardiovascular mortality for each 1 MET difference in fitness based on a multivariate analysis. The data presented in this current analysis from the Look AHEAD study provides information on the pattern of physical activity that may enhance fitness in individuals with type 2 diabetes. The data presented in Tables 2 and 3 show greater frequency (bouts per day), duration (minutes per bout), and intensity (METs per minute) of both moderate-to-vigorous (≥3 METs) and vigorous activity (≥6 METs) with greater levels of fitness, and this was confirmed by the multivariate analyses (see Tables 5 and 6). Moreover, a similar pattern was shown with self-reported LTPA with energy expenditure and sweat episodes per week were positively associated with fitness (see Table 4). Thus, while cross-sectional, these data suggest that individuals with type 2 diabetes can improve their level of fitness through participation in sufficient doses of physical activity, and according to Church et al. (3) this may reduce the risk of mortality. The data presented in this current study provide insight into the dose and pattern of physical activity that will elicit improvements in fitness in overweight and obese adults with type 2 diabetes.
It is recognized that the R2 for the multivariate models are relatively low (see Tables 5 and 6). This would suggest that the demographic factors considered in this study are collectively having modest effects on the observed patterns of physical activity in this study. Therefore, there may be additional demographic, behavioral, or physiological factors that are influencing physical activity behaviors in this group of individuals with diabetes, and this will require further examination. Moreover, the Look AHEAD Study provides a unique opportunity to examine changes in physical activity patterns prospectively and to examine factors that influence observed changes in physical activity in adults with diabetes as they age. An interesting finding is that higher levels of physical activity were consistently associated with higher levels of fitness in multivariate models after controlling for other demographic characteristics. These data may suggest that while patterns of physical activity may vary by demographic characteristics, it is important to engage in physical activity to improve fitness in patients with type 2 diabetes, and this may significantly influence the risk of mortality in this population(3).
In summary, these findings represent one of the few studies that have used objective measurement to examine the patterns of physical activity in individuals with type 2 diabetes. In this sample of over 2,000 participants in the Look AHEAD Study with diabetes, it does not appear that the vast majority of individuals meet the current recommended levels of physical activity (6, 20). However, the patterns of activity vary consistently by level of fitness, with higher levels of fitness characterized by a higher frequency, duration, and intensity of activity bouts that are moderate-to-vigorous or vigorous in intensity. In multivariate analyses there was little influence of age, BMI, type of diabetes medication, or history of cardiovascular disease on the patterns of physical activity. However, sex and race/ethnicity may influence the pattern in individuals with type 2 diabetes, and this should be considered when developing physical activity interventions in this population. The Look AHEAD Study provides an opportunity to examine changes in physical activity measured objectively using accelerometry resulting from a lifestyle intervention, which can provide valuable information on the effect of activity patterns on weight loss and other health-related outcomes in individuals with type 2 diabetes.
Supplementary Material
Acknowledgments
The results of the present study do not constitute endorsement by ACSM.
Funding and Support This study is supported by the Department of Health and Human Services through the following cooperative agreements from the National Institutes of Health: DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57154, DK57178, DK57219, DK57008, DK57135, and DK56992. The following federal agencies have contributed support: National Institute of Diabetes and Digestive and Kidney Diseases; National Heart, Lung, and Blood Institute; National Institute of Nursing Research; National Center on Minority Health and Health Disparities; Office of Research on Women's Health; and the Centers for Disease Control and Prevention. This research was supported in part by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases.
Additional support was received from The Johns Hopkins Medical Institutions Bayview General Clinical Research Center (M01RR02719); the Massachusetts General Hospital Mallinckrodt General Clinical Research Center (M01RR01066); the University of Colorado Health Sciences Center General Clinical Research Center (M01RR00051) and Clinical Nutrition Research Unit (P30 DK48520); the University of Tennessee at Memphis General Clinical Research Center (M01RR0021140); the University of Pittsburgh General Clinical Research Center (M01RR000056 44) and NIH grant (DK 046204); and the University of Washington / VA Puget Sound Health Care System Medical Research Service, Department of Veterans Affairs; Frederic C. Bartter General Clinical Research Center (M01RR01346)
Footnotes
Clinical Trial Registration Number: NCT00017953, clinicaltrials.gov
The following organizations have committed to make major contributions to Look AHEAD: FedEx Corporation; Health Management Resources; LifeScan, Inc., a Johnson & Johnson Company; Optifast ® of Nestle HealthCare Nutrition, Inc.; Hoffmann-La Roche Inc.; Abbott Nutrition; and Slim-Fast Brand of Unilever North America.
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