Abstract
BACKGROUND
The duration of rehabilitation therapy is one of the key elements for promoting post-stroke functional recovery. However, whether an individual’s age affects the effectiveness of the duration of rehabilitation therapy on post-stroke functional recovery remains unclear.
AIM
This study aimed to investigate whether age has an influence on the relationship between the duration of rehabilitation therapy and post-stroke functional recovery.
DESIGN
This is a retrospective observational study.
SETTING
Six convalescent inpatient rehabilitation hospitals in Japan.
POPULATION
The population of the study was represented by a total of 1186 participants with subacute stroke.
METHODS
Participants were stratified into four groups according to their age (≤59, 60-69, 70-79, and ≥80 years). The data of minutes involved in performing rehabilitation therapy for participants during hospitalization per day (extracted from the medical records of each hospital). The outcome measurement was the absolute change in the functional independence measure (FIM) score during hospitalization.
RESULTS
The mean FIM gains in the ≤59 years, 60-69 years, 70-79 years, and the ≥80 years groups were 38.7 (18.8), 32.8 (18.0), 29.7 (16.6), and 25.4 (17.2), respectively. The results of the multivariate regression analyses showed that there was a significant association between the duration of daily rehabilitation therapy and the FIM gain in the 70-79 years and the ≥80 years groups (-70–79 years group: B=1.289, β=0.290, 95% confidence intervals (CIs): 0.718-1.859, P<0.001; the ≥80 years group: B=2.375, β=0.371, 95% CIs: 1.644-3.107, P<0.001), but not in the other groups.
CONCLUSIONS
For patients with subacute stroke in rehabilitation hospitals, a higher duration of daily rehabilitation therapy was associated with better functional recovery in the 70-79 years group and ≥80 years groups. Understanding the responsiveness of patients with stroke to rehabilitation therapy by age group helps to better allocate medical resources and develop more effective approaches.
CLINICAL REHABILITATION IMPACT
An increased duration of daily rehabilitation therapy may be helpful in older adults with stroke selected for intensive rehabilitation for improvement of basic daily functioning.
Key words: Stroke, Rehabilitation, Activities of daily living, Aging
Stroke is one of the major causes of death and disability worldwide, and its incidence increases with age.1, 2 When the aging of the global population is combined with better acute management, the number of older stroke survivors is expected to increase.3 Upon surviving a stroke, more than half of the stroke survivors require a little assistance or are fully dependent on caregivers to perform activities of daily living (ADL) due to residual impairments.2 The limitation of daily functioning in individuals leads to decreased quality of life,4 increased caregiver burden,5 and an even worse prognosis of survival.6 Therefore, maximizing functional recovery is an important goal in stroke rehabilitation. Evidence from clinical studies supports that an increased duration of rehabilitation therapy contributes to improved functional recovery after stroke.7-10 We have also previously shown in a single-center study that patients with subacute stroke who received additional physical and occupational therapy on weekends during the rehabilitation hospital stay had better functional recovery than those who received these therapies only on weekdays.11 However, due to the limited sample size in our previous study11 and other studies, it was unclear which patients would benefit from an increased duration of rehabilitation therapy to promote functional recovery. Age may be an effect modifier for the duration of rehabilitation therapy on post-stroke functional recovery. Numerous studies have indicated that age is a robust, unmodifiable predictor of functional recovery in patients with stroke.12-15 Moreover, the stroke rehabilitation process in the older population may be modified by age-related features such as neuronal vulnerability to ischemic damage, incidence of medical complications and comorbidities, and reduced functional reserve. Indeed, factors associated with post-stroke functional recovery vary according to age demographics.15, 16 Thus, the effect of increasing the duration of rehabilitation therapy on post-stroke functional recovery may also vary based on the individual’s age. Therefore, we conducted a retrospective multicenter observational study to investigate whether age has an influence on the relationship between the duration of daily rehabilitation therapy and functional recovery in patients with subacute stroke. Clarifying the effect of increased rehabilitation time on functional recovery in each age group would help improve the management of rehabilitation systems.
Materials and methods
Participants
This study has a multicenter retrospective observational design and was conducted on patients with stroke admitted to six convalescent inpatient rehabilitation wards in three prefectures (Tokyo, Kanagawa, and Chiba) in Japan from April 2017 to December 2020. All participants met the following inclusion criteria: diagnosis of cerebral hemorrhage or cerebral infarction and independence in performing basic ADL before stroke (modified Rankin Scale score 0-2).17 Additionally, participants with any of the following were excluded from this study: death or worsening medical conditions during hospitalization (such as a recurrence of stroke or severe infection that would contraindicate rehabilitation) and the Functional Independence Measure (FIM) score on admission >108.18 The reason for excluding patients with an FIM score >108 is considered almost independent in basic ADL,18 and there is limited room for functional recovery. This study was conducted in accordance with the Declaration of Helsinki and was approved by the ethics committee of each hospital. Because this was a retrospective study, the requirement for informed consent was waived. Instead, we provided an opt-out option. Information on the study was published on the bulletin board or webpage according to the discretion of each hospital, allowing patients the opportunity to withdraw participation in the study anytime. To protect the privacy of the participants, all clinical data were anonymized. Moreover, a physical or occupational therapist at each facility was responsible for data extraction.
Rehabilitation program
All participants in this study underwent daily rehabilitation programs during hospitalization under the Japanese medical insurance system. In this system, participants are typically referred from acute care hospitals within approximately 30 days of stroke onset and receive hospital care in convalescent rehabilitation wards for up to 180 days, with a maximum of three hours of rehabilitation therapy per day.19 People who still need assistance in performing ADL after treatment in acute care hospitals and have the potential to live independently or with their families’ support by receiving intensive rehabilitation can be transferred to convalescent rehabilitation hospitals.19, 20 The timing for discharge was commonly set when patients reached a plateau in performing ADL.19, 20 Approximately 40% of all patients with stroke admitted to acute care hospitals are transferred to convalescent rehabilitation hospitals in Japan.21 All participating facilities employ a multidisciplinary team approach, following the Japanese Guidelines for the Management of Stroke.22 Rehabilitation programs were based on a comprehensive approach, which was individually designed depending on the individual’s health condition, impairment, activity limitations, and environmental and personal factors under the supervision of a rehabilitation doctor and experienced therapists. All participants in this study received physical and occupational therapies. Physical therapy focused on gait and exercise related to ADL, including gait training, balance exercise, and muscle strength exercise. Occupational therapy included upper limb exercise, cognitive training, and self-care skills training to maximize the ability to perform ADL. When necessary, participants also underwent speech language therapy and swallowing training by speech language pathologists.
Measurements
Outcome
The FIM scores23 upon admission to and upon discharge from convalescent inpatient rehabilitation wards were extracted from the medical record database of each hospital. The FIM is one of the most common measurement tools for basic ADL performance, which consists of a physical/motor domain with 13 items of evaluation and a cognitive domain with 5 items of evaluation. Tasks are rated on an ordinal scale ranging from 1 (total assistance) to 7 (complete independence), with total scores ranging from 18 to 126. We used the FIM gain, which was obtained by subtracting the admission scores from the discharge scores as the outcome measurement.24 Although the FIM is essentially an ordinal scale, the validity of using the FIM as an interval scale has been reported.25 In addition, we checked the normality and distribution of the data and determined that it was reasonable to perform arithmetic calculations. The FIM scores were recorded by expert physical or occupational therapists and nurses who were familiar with this scoring system and were recorded in the files of all participants. All medical staff who administered the FIM scores at each facility received suitable training in standardized procedures.
Other variables
Data on the demographic and clinical characteristics including age, sex, stroke type (cerebral infarction or cerebral hemorrhage), number of days from stroke onset to admission intervals (OAI), length of hospital stay (LOS), prestroke functional status, comorbidity, and the provision time of daily rehabilitation therapy were also extracted. Comorbidity was assessed using the Charlson Comorbidity Index (CCI).26 The prestroke functional status was evaluated using the modified Rankin Scale score.17 These assessments were already carried out and data were recorded in the files of all participants. We defined the duration of rehabilitation therapy as the average duration spent in daily rehabilitation sessions during hospitalization. The average duration of daily rehabilitation therapy was measured by dividing the total minutes (physical, occupational, and speech therapy) by LOS. The Japanese insurance medical system defines 20 minutes of rehabilitation therapy as one unit, with a maximum of 9 units (180 minutes) provided per day as necessary. All therapists are required to verify the start and end times of each session, and document them in the electronic medical record system.
Statistical analysis
The participants were stratified into four groups according to their age (≤59, 60-69, 70-79, ≥80 years). The normality and data distribution of variables were assessed using the Shapiro-Wilk Test and histograms. Descriptive statistics were used to assess the participants’ characteristics and outcome measures. To assess the association between the duration of rehabilitation therapy and the gain in FIM in each group, Pearson’s correlations were performed. Additionally, to investigate the impact of the duration of rehabilitation therapy on FIM gain, multivariate regression analysis was performed for each group. In multivariate analysis, age, sex, stroke type, prestroke functional status, comorbidity, OAI, LOS, and the motor and cognitive subscales of FIM on admission were used as covariates. All statistical analyses were performed using IBM SPSS (version 24.0; IBM, Armonk, NY, USA). Statistical significance was set at P<0.05.
Results
Of the 1536 enrolled patients with stroke, 350 fulfilled the exclusion criteria. Thus, a total of 1186 participants were analyzed in this study (Figure 1). The clinical and demographic characteristics of the participants are shown in Table I.
Figure 1.
—Diagram of the participants’ selection process.
Table I. —Characteristics of the four age groups of study participants.
| Parameters | Overall (N.=1186) |
≤59 years (N.=297) |
60-69 years (N.=273) |
70-79 years (N.=343) |
≥80 years (N.=273) |
|---|---|---|---|---|---|
| Age | 68.4 (13.6) | 49.5 (7.8) | 65.3 (2.9) | 74.7 (2.8) | 84.4 (3.5) |
| Sex (male) | 784 (66%) | 231 (78%) | 198 (73%) | 217 (63%) | 138 (51%) |
| Stroke type (cerebral infarction) | 760 (64%) | 133 (45%) | 165 (60%) | 244 (71%) | 218 (80%) |
| Onset to admission intervals (days) | 30.4 (15.1) | 32.1 (17.0) | 31.7 (15.7) | 29.0 (13.5) | 29.4 (13.8) |
| Length of stay (days) | 92 (55; 139) | 100 (61; 147) | 96 (59; 134) | 85 (46; 137) | 92 (56; 134) |
| Prestroke mRS (≥2) | 94 (8%) | 6 (2%) | 10 (4%) | 33 (10%) | 45 (17%) |
| Charlson Comorbidity Index (≥2) | 288 (24%) | 34 (11%) | 61 (22%) | 103 (30%) | 90 (33%) |
| FIM on admission | 67.9 (25.5) | 72.3 (24.8) | 68.1 (25.2) | 69.1 (25.0) | 61.4 (25.7) |
| Motor subscales | 45.3 (19.8) | 49.3 (19.8) | 45.4 (19.7) | 45.7 (19.3) | 40.4 (19.5) |
| Cognitive subscales | 23 (17; 30) | 23 (17; 30) | 23 (17; 30) | 25 (18; 30) | 21 (15; 28) |
| FIM at discharge | 110 (87; 119) | 116 (107; 123) | 111 (90; 119) | 107 (83; 118) | 95 (63; 113) |
| Amount of rehabilitation (min/day) | 138.2 (26.4) | 143.1 (22.3) | 135.6 (26.0) | 135.5 (28.4) | 138.7 (27.6) |
| PT (min/day) | 58.4 (17.2) | 56.4 (14.7) | 55.9 (16.7) | 58.9 (18.2) | 62.5 (18.2) |
| OT (min/day) | 54.9 (14.6) | 56.0 (12.7) | 53.0 (13.6) | 54.8 (15.6) | 55.9 (16.1) |
| ST (min/day) | 24.8 (19.0) | 30.7 (18.1) | 26.8 (19.2) | 21.8 (18.7) | 20.3 (18.7) |
| FIM gain | 31.7 (18.2) | 38.6 (18.7) | 32.8 (18.0) | 29.7 (16.6) | 25.4 (17.2) |
Values are mean (SD), median (Q1; Q2) or numbers of participants (%). FIM: functional independence measure; mRS: modified Rankin Scale; OT: occupational therapy; PT: physical therapy; ST: speech-language therapy.
The mean age and proportion of men among the study participants were 68.4 (13.6) years and 784 (66%), respectively. There were 297 participants (25%) in the ≤59 years group, 273 (23%) in the 60-69 years group, 343 (29%) in the 70-79 years group, and 273 (23%) in the ≥80 years group. Participants in all groups received an average of approximately 140 min of daily rehabilitation therapy during hospitalization. The mean FIM gains in the ≤59 years, 60-69 years, 70-79 years, and ≥80 years groups were 38.6 (18.7), 32.8 (18.0), 29.7 (16.6), and 25.4 (17.2), respectively. The number of participants who reached the maximum score of the FIM at discharge were 26 (8.8%) in the ≤59 years groups, eight (2.9%) in the 60-69 years group, nine (2.6%) in the 70-79 years group, and one (0.4%) in the ≥80 years group, respectively. Figure 2 shows the correlation between the FIM gain and the duration of daily rehabilitation therapy for each group.
Figure 2.
—The relationship between the duration of rehabilitation therapy and FIM gain: A) ≤59 years; B) 60-69 years; C) 70-79 years; and D) ≥80 years. Values are Pearson’s correlation coefficient and 95% confidence intervals.
There was a very weak to weak correlation between the FIM gain and the duration of daily rehabilitation therapy time in each group (≤59 years group: r=0.188, P=0.001; 60-69 years groups: r=0.233, P<0.001; 70-79 years group: r=0.316, P<0.001; and ≥80 years group: r=0.381, P<0.001). The results of the multivariate regression analyses for the impact of the duration of daily rehabilitation therapy on FIM gain in each age group are described in Table II.
Table II. —The results of multivariate regression analysis of the amount of rehabilitation therapy (per 10 minutes) on FIM gain.
| Parameters | B | SE B | β | 95% CI | P |
|---|---|---|---|---|---|
| ≤59 years group | 0.297 | 0.360 | 0.035 | [-0.413; 1.006] | 0.411 |
| 60-69 years group | 0.677 | 0.381 | 0.098 | [-0.072; 1.426] | 0.076 |
| 70-79 years group | 1.289 | 0.290 | 0.221 | [0.718; 1.859] | <0.001 |
| ≥80 years group | 2.375 | 0.371 | 0.381 | [1.644; 3.107] | <0.001 |
Adjusted for age, sex, stroke type, Charlson Comorbidity Index, prestroke modified Rankin Scale, onset to admission intervals, length of stay, motor subscales of the FIM on admission, and cognitive subscales of the FIM on admission. CI: confidence intervals; FIM: functional independence measure; SE: standard error.
In the ≤59 years and the 60-69 years groups, there was no significant association between the daily rehabilitation therapy time and the FIM gain (≤59 years group: β=0.035, 95% confidence intervals [CIs]: -0.413–1.006, P=0.411; 60-69 years group: β=0.098, 95% CIs: -0.072–1.426, P=0.076). On the other hand, the 70-79 years group and the ≥80 years group had a significant association between the duration of daily rehabilitation therapy and the FIM gain (70-79 years group: β=0.221, 95% CIs: 0.718-1.859, P<0.001; ≥80 years group: β=0.381, 95% CIs: 1.644-3.107, P<0.001).
Discussion
In this multicenter observational study, we investigated the effects of the duration of daily rehabilitation therapy on functional recovery in patients with subacute stroke stratified by individual’s age. We found that there were different trends among the four groups. In the 70-79 years group and ≥80 years groups, a greater number of minutes of rehabilitation therapy was significantly associated with better functional recovery. In contrast, this relationship was not observed in the ≤59 years and the 60-69 years groups. Some previous studies examined the impact of age on FIM gain as an outcome of inpatient rehabilitation among patients with acute or subacute stroke.27-29 Although there have been variations in the baseline FIM scores, OAI, and rehabilitation provision times, the results of these studies have consistently demonstrated that advanced age negatively affects the FIM gain27-29, which was also observed in this study. The FIM gain progressively decreased with advancing age, and there was a relatively large difference of approximately 12 points between the average score for the ≤59 years group and the ≥80 years group. This result may be because functional recovery in older adults with stroke can be restricted by various age-related clinical factors, such as increased comorbidity, medical complications, malnutrition, and neuropsychological impairment appropriate to the aging brain.30 It is well established that increasing the duration of rehabilitation therapy has a small but favorable effect on functional improvement in patients with stroke.7, 31 Total duration of daily therapy,9, 10 daily treatment duration of physical therapy,10, 32 occupational therapy,8, 10 and speech and language therapy10 were reportedly associated with FIM gains in patients with subacute stroke. However, little is known about which individual’s characteristics are associated with a greater benefit of augmented rehabilitation therapy time. In the present study, the positive effect of increasing the duration of rehabilitation therapy on the FIM gain was observed in the 70-79 years and the ≥80 years groups, while it was not found in the ≤59 years and–60-69 years groups. This effect is worth noting because a higher duration of daily rehabilitation therapy may be helpful for successful inpatient stroke rehabilitation for improvement of basic daily functioning in older adults who are commonly assumed to have poorer outcomes. Meanwhile, the duration of daily rehabilitation correlated with a limited percentage of the FIM gain variation even in the 70-79 years and the ≥80 years groups, which is consistent with previous studies.7, 31 These results suggest that increasing the duration of daily rehabilitation therapy can promote the improvement of basic daily functioning in patients with subacute stroke; however, it alone is not sufficient to maximize functional recovery. The relationship between the duration of rehabilitation therapy and functional recovery by age group may can be explained by changes in individual’s characteristics associated with age, such as decreased physiologic reserves, malnutrition, low physical activity level, cognitive decline, and decreased neuroplasticity. An age-related decline in physiological reserves and malnutrition accelerates various physical regressive changes associated with inactivity, such as muscle weakness and loss of muscle mass.33 In addition, older patients may require more exercise to restore motor function and relearn motor skills for performing daily activities due to limited neuroplasticity, decreased physical activity level,34 and cognitive decline.35 Therefore, more rehabilitation therapies may be needed to promote functional recovery in older patients with stroke. Meanwhile, there was no statistically significant impact of the duration of rehabilitation therapy on functional recovery in the ≤59 years group and–60-69 years group. One possible explanation is that patients with stroke in these subgroups have relatively better spontaneous recovery due to the preservation of physiological reserve and neuroplasticity than older adults.36 Additionally, patients received an average of more than two hours of rehabilitation therapy per day for about 3 months, which may have been too sufficient for younger patients to achieve maximum improvement of basic function for the individuals. In other words, there could have been a ceiling effect on the duration of rehabilitation therapy for younger patients as far as basic functional recovery is concerned. An additional battery with a more advanced functional performance or motor function can detect the effect of increasing the duration of daily rehabilitation therapy for these subgroups. In fact, some previous studies on relatively young patients with subacute stroke have shown that adding extra physical therapy or arm training had a significant effect on physical function such as walking speed37 and upper limb motor function.38, 39 Another possible reason is that there may have been a ceiling effect on the FIM score at discharge in these populations. The percentage of participants who had reached the maximum FIM score at discharge was higher among younger participants. However, the absolute number of participants who reached the maximum score was not so large. Thus, it may be limited that the ceiling effect on the FIM interfered with the significant association between basic functional recovery and duration of daily rehabilitation therapy.
Limitations of the study
This study has some limitations. First, this study was retrospective in nature; hence, we could not evaluate several important covariates such as the National Institutes of Health Stroke Scale,40 the Fugl-Meyer Motor Scale, the patient’s level of fatigability, and the detailed contents of rehabilitation therapy in convalescent rehabilitation hospitals and acute care hospitals. For example, the duration of daily rehabilitation therapy could be impacted by the severity of stroke or the fatigability of the patients. People with severe condition or low endurance may not be able to tolerate intensive rehabilitation; thus, the rehabilitation team might oblige to adjust the duration of daily rehabilitation therapy. Furthermore, the timing of the assessment was not according to the timing of the post-stroke symptom onset. The ideal would have been to investigate the functional progress over the same period in terms of functional delay post-stroke. These limitations related to the retrospective design potentially influenced the current results. Future studies should examine the effects of the duration of rehabilitation in clinical trials using standardized exercise types and intensities. Second, the severity of disability of the participants was moderate, and this study was conducted in a Japanese convalescent rehabilitation setting. Extrapolation of the present findings to these participants may be limited because patients with milder disease severity or those more severely affected and who were not fitted for convalescent rehabilitation in the Japanese medical insurance system were not included in this study. The strength of this study is that this was a multicenter study on a large number of participants, and the number of missing participants was relatively small. We consider that the merit of the large sample size and exhaustive nature of the collection of the main variables of the current study may partly compensate for the aforementioned limitations.
Conclusions
In conclusion, for patients with subacute stroke in rehabilitation hospitals, a higher duration (in minutes) of daily rehabilitation therapy was associated with better functional recovery in the 70-79 years group and ≥80 years groups. In contrast, this relationship was not observed in the ≤59 years group and–60-69 years group. These results indicate that an increased duration of daily rehabilitation therapy may be helpful in older adults with stroke selected for intensive rehabilitation for promoting basic functional recovery. The findings of this study have significant implications for the development of stroke rehabilitation services in an aging society to achieve better functional outcomes among older adults with stroke.
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