Sedentary behaviour may cause differences in physical outcomes and activities of daily living in older cardiovascular disease patients participating in phase I cardiac rehabilitation

This study aimed to investigate the rate of sedentary behaviour and differences in physical outcomes and activities of daily living (ADL) based on sedentary behaviour time of hospitalized older cardiovascular disease patients undergoing phase I cardiac rehabilitation. Older cardiovascular disease patients were enrolled from October 2020 to September 2023 and were divided into the high sedentary behaviour group (≥ 480 min/day) and low sedentary behaviour group (< 480 min/day). Patients’ clinical characteristics, usual gait speed, and Five Times Sit to Stand Test time were compared as indices of physical outcomes. Motor, cognitive, and total Functional Independence Measure (FIM) scores were used as indices of ADL and compared between groups using analysis of covariance. Final analysis included 402 patients (mean age: 76.7 years, female: 35.3%). The high sedentary behaviour group included 48.5% of the study patients. After adjustment for baseline characteristics, gait speed (0.80 ± 0.27 vs. 0.96 ± 0.23 m/s, p < 0.001) was lower and FTSST time (11.31 ± 4.19 vs. 9.39 ± 3.11 s, p < 0.001) was higher in the high sedentary behaviour group versus low sedentary behaviour group. Motor (85.82 ± 8.82 vs. 88.09 ± 5.04 points, p < 0.001), cognitive (33.32 ± 2.93 vs. 34.04 ± 2.24 points, p < 0.001), and total FIM scores (119.13 ± 10.66 vs. 122.02 ± 6.30 points, p < 0.001) were significantly lower in the high sedentary behaviour group versus low sedentary behaviour group after adjustment. In older cardiovascular disease patients in phase I cardiac rehabilitation, sedentary behaviour time might influence physical outcomes and ADL at discharge. It is thus important to consider the amount of sedentary behaviour time spent by these patients during daily life while hospitalized.

The patients were also asked to answer a cognitive function questionnaire (Mini Mental State Examination) at discharge.

Sedentary behaviour time
We used the Workforce Sitting Questionnaire 30 to evaluate SB time.This questionnaire, whose reliability and validity have already been confirmed in Japan 31 , includes six items related to SB time over 1 week that assess driving, transportation, work, television viewing, personal computer/smartphone use, and other leisure time activity 28,31 .As the older CVD patients were hospitalized, 0 min were assigned to the items of driving and transportation times 28,31 .Each item was answered for workdays and non-workdays over a 7-day period.After the questionnaires were collected by a researcher, total SB time in min/day as it related to the six items over the 7-day period was calculated as total SB time in minutes ÷ 7 days 28,31 .Therefore, SB time measured for the entire day was considered to indicate SB.We then divided the patients into two groups according to a cutoff value for SB time of 480 min/day (low SB group: < 480 min/day and high SB group: ≥ 480 min/day) as described in a previous study 28,32 .

Gait speed and Five Times Sit to Stand Test to assess physical outcome
GS and the FTSST were used as indices of physical outcome in the present study.Usual GS was measured over a 4-m distance on a flat floor with a total pathway length of 6 m 28 .We instructed each participant to walk the 6-m distance as fast as possible without falling.The time taken to walk the 4-m distance in the middle of the 6-m-long walking path was measured using a stopwatch.The measurement was conducted twice and the shorter time was used [21][22][23]28 . TheFTSST requires the patients to cross their arms across their chest, stand up from a chair, and return to a seated position five times as quickly as possible.AWGS 2019 considers GS < 1.0 m/s and FTSST ≥ 12 s as criteria for low physical performance indicative of sarcopenia 23 .

Motor, cognitive, and total FIM for ADL
The primary outcome measure for ADL was the FIM score 33,34 .The FIM comprises 18 items, each scored on a scale of one to seven points.The total FIM score ranges from 18 to 126 points and reflects the level of dependence in actual ADL.The FIM is divided into the motor domain, which includes 13 items related to physical movements, such as self-care, sphincter control, transfers, and locomotion, and the cognitive domain, consisting of five items for assessment of communication and social cognition.A higher FIM score indicates greater independence in ADL.At discharge, one or three CR staff members assessed each patient's GS, FTSST, and FIM results.

Statistical analysis
Results are expressed as the mean ± standard deviation (SD).We used parametric and chi-square tests to analyse differences between the high SB and low SB groups.Additionally, we used an unpaired t-test to assess differences in clinical characteristics between the two patient groups.To compare GS, FTSST, and motor, cognitive, and total FIM values between the groups, we performed a one-way analysis of covariance (ANCOVA) with relevant variables as covariates.These covariates were selected based on significant differences observed in clinical characteristics between the two groups using chi-square analyses and t-tests.A p-value < 0.05 was considered statistically significant.For our analyses, we used IBM SPSS 29.0 statistical software 35 , which was developed by IBM SPSS Japan, Inc.

Ethical approval
This study was approved by the Institutional Review Board for Ethics at the Graduate School of Health Sciences, Kobe University (Approval No. 951-2), and each affiliated hospital received approval from its local ethics committee.

Informed consent
Informed consent was obtained from each patient.

Flow chart of study participants
Among 11,504 CVD patients admitted to the affiliated hospitals during the study period, 3606 patients met the inclusion criteria, including being hospitalized for more than 5 days and undergoing phase I CR.After excluding 3204 patients who met the exclusion criteria, 402 patients (mean age: 76.7 years, female: 35.3%) were finally included.A flow chart of the study participants is shown in Fig. 1.

Patient characteristics between the high SB and low SB groups
Clinical characteristics of the patients between the high SB group and low SB group can be compared in Table 1, which shows that the high SB group comprised 48.5% (195 of 402) of the older CVD patients.There were significant differences in age, employment, main diagnosis, and SB time between the two groups.

Assessments of physical outcome between the high SB and low SB groups
The results showed that GS (0.80 ± 0.27 vs. 0.96 ± 0.23 m/s, p < 0.001) was significantly lower and FTSST time (11.31 ± 4.19 vs. 9.39 ± 3.11 s, p < 0.001) was significantly higher in the high SB group versus low SB group after adjusting for clinical characteristics (Table 2, Fig. 2).   3 and 4).

Discussion
This study examined the differences in physical outcomes and ADL among older CVD patients based on their SB time.Although several previous studies have investigated the impact of SB time and/or physical activity in hospitalized patients 9,15,16 , the present study specifically focused on older CVD patients.We investigated the cutoff values of SB time based on methods used in previous studies 28,32 .In a recent study in Japan, Kono et al. reported that non-lying time could be one of the associated factors of HAFD in older patients undergoing TAVI 17 .They suggested that non-lying time of about 480 min (8 h) per day during hospitalization may be an initial target for preventing HAFD.Therefore, on the basis of this previous study, we considered this cutoff value used for SB time to be appropriate.Cattanach et al. previously reported that patients were observed to be in bed 51% of the time and sitting out of bed 43%, standing 1%, and walking 5% of the time.The response to a questionnaire they used indicated that one third of the participants were not observed to walk during the observation period, and, moreover, 38% of the participants had expected to remain in bed while in hospital 15 .Even though the assessment methods between   their study and ours were different, the present study showed a high rate of SB of 48.5%.Our previous study 28 , which included both middle-aged and older patients, showed a high rate of SB of 47.6%.However, the rate of SB was higher in the present study as it was limited only to older patients.In other previous studies, although diseases and ages of the study patients were different, the older patients tended to engage in more sitting SB time and spend more time in bed 13,14 .In their systematic review, Harvey et al. 36 suggested that older adults (age ≥ 60 years) are one of the most sedentary groups in society, spending on average 80% of their time in a seated posture with 67% being sedentary for more than 8.5 h per day.In the present study, the total sitting SB time in the high SB group was 718.42 min/day, i.e., approximately 11.97 h/day.Because SB occurred primarily during leisure time, outside of phase I CR, the greatest reduction in total SB time of older CVD patients with high SB can likely be achieved by targeting their leisure time sedentary activities during hospitalization.We consider it important to address this problem beginning in phase I CR because as Chastain et al. 37 reported, the effectiveness of interventions to reduce SB in community-dwelling older adults remains unclear.There were significant differences in the characteristics of age, employment, and main diagnosis between the patients in the two study groups.Notably, these factors largely align with predictors of high SB levels in the general population and of several diseases 9,20,26,27,38,39 .Our findings suggest that these factors may also impact high SB levels in older CVD patients.
With regard to physical outcomes, GS was lower and FTSST time was higher (Table 2, Fig. 2) in the high SB versus low SB group after adjusting for baseline characteristics.Individuals with a GS below 1.0 m/s are at high risk for leg injury, hospitalization, and death 22,40 .In the programming of pedestrian traffic signals in Japan, a GS of 1.0 m/s or faster is required to cross the street within the programmed period 22 .Thus, having a GS of 1.0 m/s or faster is an important ability needed for various public activities such as shopping, hobbies, and work after discharge from hospital.The value was close to 1.0 m/s for the low SB group but was much lower than 1.0 m/s for the high SB group.
The FTSST time in the high SB group was 11.31 s, similar to the low physical performance value indicated in AWGS 2019 (≥ 12 s) 23 .In addition, Camarzana et al. recently suggested that the FTSST was an independent predictor of 1-year mortality in patients with severe aortic stenosis who did not undergo valve replacement (59 patients; age, 86.1 years) 41 .Therefore, the reserve capacity for GS in the high SB group is low, and FTSST time is high, indicating that special attention should be paid to older CVD patients.
Motor, cognitive, and total FIM scores were significantly lower in the high SB group compared to the low SB group (Table 2, Figs. 3 and 4).A previous study aimed to identify predictive factors for ADL as assessed by FIM at discharge in older heart failure patients with preserved ejection fraction.The receiver operating characteristic curves yielded cutoff values for predicting ADL at discharge of 34.5 points for the motor FIM score and 28.5 points for the cognitive FIM score.Notably, the motor and cognitive FIM scores in the high SB group of the present study included patients with scores above these reported thresholds, potentially minimizing the impact of SB on discharge results.However, other previous studies have suggested that FIM scores at discharge serve as independent predictors of re-admission and mortality at 90 and 180 days in CVD patients 25,42 .Kitamura et al. further classified older heart failure patients into four groups based on a previous study's cutoff values for the Geriatric Nutritional Risk Index (GNRI), an index of nutrition, and motor FIM.They reported that the rate of readmission avoidance was significantly lower in the group with GNRI < 92 and motor FIM < 75 within 90 days of discharge 25 .
Iwata et al. also investigated the prognostic impact of the FIM score on clinical outcomes in hospitalized patients with acute decompensated heart failure.They retrospectively analysed 473 patients with available predischarge FIM scores admitted to their institution.The primary outcome measures, defined as a composite of 180-day all-cause deaths and readmissions, were compared among three tertiles 42 .The median total FIM score was 102 (interquartile range: 85-115).Tertile 1 corresponded to an FIM score > 111, Tertile 2 to that of 90-111, and Tertile 3 to that of < 90.Even after multivariable adjustment, the results remained significant [Tertile 1 vs. 3: adjusted hazard ratio, 3.28; Tertile 2 vs. 3: 2.32].FIM scores were significantly associated with readmission or death within 180 days of discharge in these hospitalized heart failure patients 42 .www.nature.com/scientificreports/Evaluation of FIM scores at the time of discharge, especially in relation to high SB, is crucial.Additionally, prognosis after discharge must be considered and measures implemented with a view to continuing phase II CR.Although our study focused on phase I CR, it is worth noting that in a different context (long-term acute care hospitals for patients after stroke), changes in FIM scores associated with the minimal clinically important difference were 22 points for total FIM, 17 points for motor FIM, and 3 points for cognitive FIM scores 43 .Although we did not specifically examine improvement in pre-versus post-FIM scores during phase I CR, ADL of the high SB group were significantly lower at discharge.Thus, older CVD patients with high SB are likely to experience not only loss of motor function but also a decline in cognitive function related to ADL in the future.It may be necessary for staff in charge of phase I CR to intervene for patients with SB during hospitalization to improve their ADL.
Our study also showed that high age, heart failure, and unemployment tended to be associated with high SB.As mentioned earlier, even though hospitalized patients with acute heart failure infrequently experience hospital-associated disability, only 44% of these patients were accepted into phase I CR 8 .Therefore, greater attention should be paid to these factors during phase I CR.Early mobilization to reduce SB, early screening for sarcopenia, and implementing aerobic exercise and resistance training during hospitalization are essential components of phase I CR.
The recent systematic review by Chastin et al. suggested that it remains unclear whether interventions to reduce SB are effective in decreasing sedentary time in community-dwelling older adults 37 .Furthermore, the impact of these interventions on the physical and mental health of community-dwelling older adults remains uncertain.Thus, further research is necessary to explore interventions aimed at reducing high SB and improving both physical outcomes and ADL of older CVD patients during phase I CR.

Limitations
The present study has several limitations.First, the study is constrained by its small sample size and the limited number of female patients, which hindered the assessment of sex-related differences.Second, many of the older CVD patients were hospitalized solely for therapeutic interventions, such as pacemaker battery replacement, and were therefore excluded from this study, which may have introduced selection bias.Third, the study included various CVDs as the primary diagnosis, along with comorbidities requiring different treatments.Fourth, a selfreported subjective questionnaire was used to assess SB time, and the study lacked objective measurements made by a versatile device with various features and tools.Fifth, we could not investigate the relationship between SB time and prognosis, including re-admission rates and mortality.Notably, SB has been linked to acute detrimental effects on vascular function, blood pressure, and lipid levels, which may contribute to the risk of cardiovascular events and mortality 26,27,44 .Finally, it might be more insightful to report a comparison between values at baseline and the end of phase I CR to investigate effects of the multidisciplinary intervention on SB and how SB could be affected in both groups (e.g., would most inactive patients benefit from the intervention, or would they be more reluctant to participate in such a program in the first place?).In future trials, we will need to investigate differences in disease severity as they relate to SB to determine whether specific forms of intervention should be applied based on this analysis.

Conclusions
This study investigated the impact of SB on physical outcomes and ADL of hospitalized older CVD patients undergoing phase I CR.We found that the high SB group had lower GS and longer FTSST times compared to the low SB group.Additionally, motor, cognitive, and total FIM scores for ADL were significantly lower in the high SB group, even after adjusting for other associated factors.These findings suggest that SB time may influence physical outcomes and ADL at discharge of older CVD patients participating in phase I CR.Therefore, it is essential to consider levels of SB during CR and encourage older CVD patients to engage in more physical activity while in hospital (Supplementary Fig. 1).

Figure 1 .
Figure 1.Flow chart of the study participants.CVD cardiovascular disease, PCI percutaneous coronary intervention.

Figure 2 .
Figure 2. Comparison of the physical outcomes of GS and FITTS between the high SB group and low SB group.FITTS Five Times Sit to Stand Test, GS gait speed, SB sedentary behaviour.

Figure 3 .
Figure 3.Comparison of motor and cognitive FIM scores for activities of daily living between the high SB group and low SB group.FIM Functional Independence Measure, SB sedentary behaviour.

Figure
Figure Comparison of total FIM scores for activities of daily living between the high SB group and low SB group.FIM Functional Independence Measure, SB sedentary behaviour.

Table 1 .
Clinical characteristics of the patients in the high SB and low SB groups.SB sedentary behaviour, ACE-I angiotensin-converting enzyme inhibitor, ARB angiotensin II receptor blocker.

Table 2 .
Physiological outcomes and ADL in the high SB and low SB groups.SB sedentary behaviour time, GS gait speed, FTSST Five-Times-Sit-To-Stand Test, ADL activities of daily living, FIM Functional Independence Measure.*Mean ± standard deviation.Adjusted for baseline characteristics.