Highlights
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Light physical activity increased during a 6-week cardiac rehabilitation program.
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Sitting time and moderate physical activity did not improve until after 6 weeks.
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We found no further change in sitting time and moderate physical activity from 6 to 12 months.
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Sitting time was high and physical activity levels were low over 12 months.
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An increased focus on sitting time is indicated in cardiac rehabilitation.
Abstract
Background
International cardiac rehabilitation guidelines recommend that participants meet public health physical activity guidelines. Few studies have objectively measured how much time cardiac rehabilitation participants spend in physical activity and sedentary behaviour, particularly over the long term.
Objective
The aim of this study was to objectively assess physical activity and sedentary behaviour of cardiac rehabilitation participants over 12 months and determine whether they met the public health physical activity and sedentary behaviour guidelines.
Methods
Cardiac rehabilitation participants with coronary heart disease were recruited in a prospective cohort study ( n = 72). Participants wore an ActiGraph ActiSleep accelerometer for 7 consecutive days at baseline, 6 weeks, and 6 and 12 months to assess daily minutes of moderate-to-vigorous physical activity and sedentary behaviour (< 100 counts/min). Other outcomes collected were self-reported physical activity and sedentary behaviour, body mass index, waist-to-hip ratio, lipid profile, blood glucose level, quality of life, exercise capacity, anxiety and depression.
Results
By intent-to-treat analysis, during the 6-week cardiac rehabilitation program, participants increased their light physical activity ( P < 0.01), which was maintained up to 12 months. Moderate-to-vigorous physical activity and sedentary behaviour did not change during the 6-week cardiac rehabilitation program but did improve over 6 months (sedentary behaviour decreased [ P < 0.001], moderate-to-vigorous physical activity increased [ P < 0.05]), which was maintained up to 1 year. Completion of moderate-to-vigorous physical activity in 10-min bouts did not change over 12 months, nor did the proportion of participants meeting physical activity guidelines (15–21%). Sedentary behaviour remained high throughout (11 hr/day).
Conclusion
Most cardiac rehabilitation participants did not meet the physical activity guidelines during and after a 6-week program up to 12 months. Reducing sedentary behaviour may be a more achievable first-line strategy for cardiac patients, moving participants along the energy expenditure continuum, aiming to increase their physical activity levels over the medium to long term.
Trial registration
Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12615000995572, http://www.ANZCTR.org.au/ACTRN12615000995572.aspx.
1
Introduction
Physical activity and sedentary behaviour are independent risk factors for cardiovascular disease (CVD) and all-cause mortality . This association appears to be the same in healthy and CVD populations . Cardiac rehabilitation is the coordinated system of care necessary to help people with coronary heart disease (CHD) return to an active and satisfying life and helps to prevent the recurrence of cardiac events or new cardiovascular conditions . International cardiac rehabilitation guidelines recommend that participants aim to achieve the public health physical activity guidelines . However, none of the guidelines provide recommendations on reducing sedentary behaviour.
There is strong evidence that the more time people are sedentary, the more likely they are to develop or die from CVD or any cause ; however, this association appears to be altered with increasing amounts of moderate-intensity physical activity and potentially eliminated by completing high levels of moderate-intensity physical activity daily (> 60 min/day) . The evidence regarding how one accumulates sedentary time and its effects on health is less clear. Currently, we have insufficient evidence to determine whether bouts or breaks in sedentary behaviour are important factors in the association between sedentary behaviour and CVD incidence as well as CVD and all-cause mortality . There is some evidence that increasing the interruptions to sedentary time decreases waist circumference, and brief interruptions to sitting time (2 min of physical activity) every 20 min leads to significant reductions in post-prandial glucose and insulin levels, but this research is still emerging .
A recent meta-analysis of 1 million participants suggested that a threshold > 7 hr (self-reported) and 9 hr (objective measures) of sedentary time was associated with poor health . Rogerson et al. examined the association between sedentary behaviour and all-cause mortality in people with CVD ( n = 609), with television viewing time used as a marker of sedentary behaviour : as compared with watching < 2 hr/day, watching ≥ 4 hr/day of television increased all-cause mortality 52%. Therefore, physical activity and also sedentary time must be considered in the secondary prevention of CVD.
Few studies have objectively measured the physical activity and sedentary behaviour of cardiac rehabilitation patients, particularly over the long term. Physical activity levels have been reported as low (approximately 11 min/day moderate-intensity physical activity ) and sedentary behaviour high (approximately 8–10 hr/day ).
The aim of this study was to objectively assess the physical activity levels and sedentary behaviour of cardiac rehabilitation participants over 12 months to determine whether participants were meeting the Australian physical activity and sedentary behaviour guidelines .
2
Methods
Using a prospective cohort study design, 72 participants aged ≥ 18 years and enrolled in the 6-week Australian hospital-based phase II cardiac rehabilitation program were recruited to the 12-month observational study between November 2015 and August 2016. Participants were included if they had stable CHD and were receiving optimal medical treatment with or without revascularisation . All participants provided written consent. The study protocol and 6-week results have been described elsewhere . During the 6-week cardiac rehabilitation program, participants attended approximately 12 exercise and 12 education sessions, with 1 education session on exercise and physical activity. Sedentary behaviour was not discussed in this session. Ethics approval was received from the ACT Health Human Research Ethics Committee in August 2015 (Project reference: ETH.5.15.076).
2.1
Outcome measures
A triaxial commercial accelerometer (ActiGraph ActiSleep, Fort Walton Beach, FL) was used to objectively assess sedentary behaviour and physical activity . Participants were asked to wear the monitor on their right hip for 24 hr/day for 7 consecutive days. All data were downloaded and screened; we excluded data with < 10 hr/day wear time (non-wear defined as > 60 consecutive minutes of zero activity, allowing for 2 min of counts between 0-100) and < 4 days of valid data. The raw data (counts) collected by the accelerometer were then used to obtain the time spent in different physical activity intensities. The Freedson Combination energy expenditure algorithm was used to determine physical activity and sedentary behaviour (< 100 counts/min) intensity cut-points . Moderate-to-vigorous physical activity bout data used a minimum bout length of 10 min, with a tolerance of 2 min. Sedentary behaviour bout data used a minimum length of 10 min, with no drop time . Estimating time spent in physical activity and sedentary behaviour was calculated by dividing the total time spent (minutes) in each threshold by the number of valid days . A break is an interruption in sedentary time (> 100 counts/min). Sleep time was eliminated by using a time filter applied from 0700 to 2230 hr, the average wake and sleep time reported by participants. Adherence to the physical activity recommendations, 150 min of moderate-to-vigorous physical activity per week (sufficient time), was calculated for 1-sec epoch and 10-min bout data . To determine whether participants met the World Health Organisation physical activity guidelines, sufficient time in 10-min bouts was used . Calculations were based on estimates of daily minutes in moderate-to-vigorous physical activity and multiplied by 7 to estimate a week.
Secondary outcomes included subjective reporting of sedentary behaviour (Past-Day Adults’ Sedentary Time questionnaire [PAST] ) and physical activity (Active Australia Survey [AAS] ); body mass index (BMI, kg/m 2 ); waist and hip circumference; resting blood pressure; fasting blood lipid and glucose levels; exercise capacity (6-min walk test [6MWT] ); health-related quality of life (MacNew Heart Disease Health-related Quality of Life Questionnaire [HRQoL] ), with scores from 1, low HRQoL, to 7, high HRQoL; and anxiety and depression (Hospital Anxiety and Depression Scale [HADS], with maximal score 21 for either, high scores indicating high anxiety and depression ). Adherence to physical activity guidelines, 150 min of moderate-to-vigorous physical activity per week (sufficient time), was also calculated by using the AAS (self-report) data. Sociodemographic and other clinical information were collected. Outcome measures were assessed at baseline, 6 weeks, and 6 and 12 months.
3
Statistical analysis
Intent-to-treat analysis was used. For missing data at follow-up, the last value was brought forward. Additionally, for accelerometer data, a less conservative approach (per-protocol analysis) involved only participants who had valid accelerometer results. Descriptive analyses were completed. Normality of the data was assessed by the Kolmogorov–Smirnov test. For data that were normally distributed, repeated-measures ANOVA was used to test for differences within the cohort. If variables were not normally distributed, the Friedman test was used. The significance level was set at P < 0.05. All data were analysed with SPSS v23 (Chicago, IL).
4
Results
At 6 weeks and 6 and 12 months, 85% (61/72), 78% (56/72) and 69% (50/72) of participants, respectively, completed assessments ( Fig. 1 ). The main reason for non-attendance at follow-up assessments was work, travel or health problems. Overall, 63 participants provided valid accelerometer results at baseline, 54 at 6 weeks, 40 at 6 months and 33 at 12 months. Participants were mostly male (79%), born in Australia (66%), obese (BMI ≥ 30 kg/m 2 ), post-secondary school educated (72%) and in a relationship (70%) . The mean (SD) age was 64.2 (9.6) years. Half of the participants (52%) were working at the start of the program. Most (81%) were admitted for percutaneous coronary intervention, most were taking blood pressure medications (86%) and cholesterol-lowering medications (90%), and they reported high HRQoL and low levels of anxiety and depression ( Table 1 ). Participants’ blood pressure and lipid levels were normal, but their blood glucose level was elevated: mean 6.1 (1.7) mmol/L (normally 3.5 to 5.5).
| Baseline | 6 weeks | 6 months | 12 months | |
|---|---|---|---|---|
| Waist circumference (cm) | 106.8 (13.6) | 106 (13.8) | 105.7 (14.5) | 106 (14.7) |
| Waist-to-hip ratio | 0.97 (0.07) | 0.97 (0.06) | 0.97 (0.07) | 0.97 (0.07) |
| Body mass index (kg/m 2 ) | 30.1 (5.0) | 29.7 (5.9) | 29.9 (5.3) | 29.7 (6.2) |
| Systolic blood pressure (mmHg) | 126 (13) | 123 (14) | 126 (13) | 126 (12) |
| Diastolic blood pressure (mmHg) | 71 (8) | 68 (7) b | 72 (7) c | 74 (7) d |
| MacNew Global (/7) | 5.6 (0.8) | 6 (0.7) e | 6 (0.7) | 6 (0.7) d |
| MacNew Physical (/7) | 5.2 (0.9) | 5.9 (0.7) e | 6 (0.8) | 5.9 (1.1) d |
| MacNew Social (/7) | 5.5 (1.0) | 6.2 (0.8) e | 6.4 (0.7) c | 6.3 (1.1) d |
| MacNew Emotional (/7) | 5.8 (0.9) | 6.1 (0.7) e | 6 (0.7) | 6 (0.8) d |
| HADS-Anxiety (/21) | 3.8 (3.4) | 3.3 (2.9) | 3.6 (3.2) | 3.5 (3) |
| HADS-Depression (/21) | 3.0 (2.7) | 2.2 (2.4) b | 2.4 (2.7) | 2.4 (2.5) f |
| HADS-total (/42) | 7.0 (5.5) | 5.4 (4.8) e | 5.9 (5.2) | 6 (4.9) g |
| Total cholesterol (mmol/L) | 3.8 (1.1) | 3.6 (0.9) | 3.7 (1.2) | 3.8 (1.2) |
| Triglycerides (mmol/L) | 1.4 (0.8) | 1.3 (0.6) | 1.3 (0.7) | 1.3 (0.7) |
| Low-density lipoprotein (mmol/L) | 1.9 (0.8) | 1.8 (0.6) | 1.9 (0.9) | 1.9 (1) |
| High-density lipoprotein (mmol/L) | 1.1 (0.2) | 1.1 (0.2) | 1.2 (0.3) c | 1.2 (0.2) d |
| Blood glucose level (mmol/L) | 6.1 (1.7) | 5.9 (1.4) | 6.1 (1.4) | 6.4 (2.1) |
| 6-min walk test distance (m) | 487.0 (85.6) | 531.6 (94.9) h | 546 (104.7) | 550.6 (110) i |
a All comparisons were not significant unless otherwise indicated.
b P < 0.01 comparing baseline to 6 weeks, paired comparison Wilcoxon Signed Rank test.
c P < 0.001 comparing 6 weeks to 6 months, paired comparison Wilcoxon Signed Rank test.
d P < 0.001 comparing baseline to 12 months, paired comparison Friedman test.
e P < 0.001 comparing baseline to 6 weeks, paired comparison Wilcoxon Signed Rank Test.
f P < 0.01 comparing baseline to 12 months, paired comparison Friedman test.
g P < 0.05 comparing baseline to 12 months, paired comparison Friedman test.
h P < 0.001 comparing baseline to 6 weeks, paired t test.
i P < 0.001 comparing baseline to 12 months, paired comparison repeated measures ANOVA.
Diastolic blood pressure, high-density lipoprotein level and 6MWT distance increased over 12 months, with improvement in HRQoL (MacNew) and depression (HADS) ( Table 1 ). Diastolic blood pressure decreased during the 6-week cardiac rehabilitation program, then increased to 6 months with no further significant changes. High-density lipoprotein level did not change during the cardiac rehabilitation program but increased from 6 weeks to 6 months and was maintained to 12 months. HRQoL (MacNew, all domains), HADS depression and total scores, and 6MWT distance improved during the 6-week cardiac rehabilitation program, with no further improvement to 12 months except for the MacNew social domain, which continued to improve by 6 months ( Table 1 ).
Accelerometry measures of minutes per day spent in moderate-to-vigorous physical activity and light physical activity significantly increased over 12 months, and time spent in sedentary behaviour significantly decreased ( Table 2 ). During the 6-week program, only light physical activity significantly increased, with no changes in moderate-to-vigorous physical activity or sedentary behaviour. After the 6-week program, light physical activity was maintained to 12 months. Moderate-to-vigorous physical activity increased and sedentary behaviour decreased by 6 months, with no further changes at 12 months. Accelerometer wear-time decreased from 6 weeks to 6 months (832 vs. 780 min/day, P < 0.001). Fig. 2 graphically depicts the changes in physical activity and sedentary behaviour over time as a percentage of wear-time.
| ActiGraph 1 sec | ActiGraph 10-min bout | Self-report | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Baseline | 6 weeks | 6 months | 12 months | Baseline | 6 weeks | 6 months | 12 months | Baseline | 6 weeks | 6 months | 12 months | |
| MVPA (min/day) | 39 (23) | 40 (24) | 44 (24) b | 45 (25) c | 10 (14) | 10 (15) | 10 (13) | 10 (15) | 43 (32) | 58 (46) d | 71 (61) b | 82 (70) c |
| LPA (min/day) | 73 (22) | 82 (30) e | 85 (26) | 84 (26) f | ||||||||
| Sufficient PA (time) ( n , %) | 49 (78) | 52 (79) | 53 (79) | 54 (81) | 10 (16) | 10 (15) | 12 (18) | 14 (21) | 40 (73) j | 50 (81) d,j | 49 (78) j | 51 (81) g,j |
| SB (min/day) | 723 (58) | 711 (66) | 651 (81) h | 648 (79) c | 259 (93) | 229 (89) i | 154 (106) h | 144 (103) c | 586 (190) | 610 (219) | 623 (219) | 623 (217) |
| SB bouts/day | 13.1 (4) | 11.7 (4.1) i | 8.4 (4.9) h | 8 (4.8) c | ||||||||
| SB breaks/day | 13 (4) | 11.6 (4.1) i | 8.2 (4.9) h | 7.8 (4.8) c | ||||||||
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