Characteristics of Early Postoperative Sedentary Time in Patients with Hip Fractures

ABSTRACT

Objectives: This study aimed to investigate the sedentary time of patients with hip fractures, including those with cognitive decline, in the early postoperative period.

Methods: Participants were patients with hip fractures treated at our hospital. A triaxial accelerometer was attached to the contralateral hip, and activity was recorded for three postoperative days (4320 min).

Results: Thirty patients (mean age: 86.5 years; female, n=23) were included in the analysis. The mean activity times were: sedentary time, 1364.0 ± 59.9 min/day (mean ± standard deviation); light-intensity physical activity time, 71.9 ± 57.8 min/day; and moderate-to-vigorous-intensity physical activity time, 4.1 ± 3.2 min/day. Sedentary time was linked to the scores on the Mini-Mental State Examination-Japan.

Conclusions : Early postoperative patients with hip fractures have long sedentary times and less time for moderate-to-vigorous-intensity physical activity. Patients with hip fractures with cognitive decline have significantly longer sedentary time than those without cognitive decline.

INTRODUCTION

Numerous studies have examined physical activity in patients with hip fractures.¹⁾ However, patients with cognitive decline have frequently been excluded from such studies.^2,3,4,5,6,7) Because many patients with hip fractures have cognitive decline (41.8%),⁸⁾ the physical activity reported in previous studies may differ from the actual physical activity in patients with hip fractures. For example, given that patients with cognitive decline lack spontaneity, it is assumed that patients with hip fractures with cognitive decline will have longer sedentary time than those without cognitive decline. This study aimed to investigate early postoperative sedentary time in patients with hip fractures, including those with cognitive decline.

MATERIALS AND METHODS

Study Design

This single-institution, prospective observational study was conducted at a secondary emergency hospital and did not use a comparative group. Eligible patients were treated in the orthopedic surgery ward (46 beds, 7:1 nursing ratio). Eight physical therapists and seven occupational therapists were assigned to the unit.

Rehabilitation Interventions

The hospital provides rehabilitation throughout the year, with physical and occupational therapy starting on the day of admission or the day after. Postoperative bed rest was maintained until rehabilitation intervention. Post-surgical therapy was determined based on surgical and radiographic findings after a discussion between the doctor and physical or occupational therapist. Following assessment of the wound and the patient’s general condition by a doctor, the physical or occupational therapist commenced the standing and walking exercises the day after surgery.

Participants

Patients admitted to our hospital for hip fractures were included in this study. The following exclusion criteria were used: age less than 65 years, conservative treatment, lack of independence in indoor ambulation before injury, admission from outside the home (including facilities treated as home in the healthcare system), high-energy trauma fractures, fractures at other sites, motor paralysis caused by pre-existing central nervous system disease, difficulty with our standard postoperative rehabilitation interventions (<80 min and weight restrictions), and transfer to another ward. The target number of cases was set at 30 to ensure a larger sample size than that in previous studies^2,4) (20 and 13 cases, respectively) and to account for dropouts.

The purpose and content of the study were fully explained to the participants, family members, or other proxies orally and in writing, and their written consent to participate in the study was obtained. The Ethical Review Committee for Clinical Research at Aizawa Hospital approved this study (approval number: 2021–056; October 21, 2021).

Primary Endpoint: Sedentary Time and Physical Activity

A triaxial accelerometer (Active style Pro HJA-750C; Omron Healthcare, Kyoto, Japan) was used to measure physical activity. Triaxial accelerometers have been shown to accurately estimate even low-intensity physical activity⁹⁾ and have been used to study physical activity in older adults.¹⁰⁾ The epoch length used for the measurements was 10 s. Metabolic equivalent of task (MET) was used as the measurement index. The waist portion of the pants on the contralateral side was used as the accelerometer wear site. The device was secured with an attached wear holder and a clip with a strap. Measurements were obtained throughout the hospital stay, excluding bathing.

Many patients with hip fractures have cognitive decline and may not properly handle the triaxial accelerometer themselves (e.g., touching or vibrating the device may cause overestimation of physical activity). Therefore, physical therapists, occupational therapists, and nurses in charge of the patients observed them throughout the day to ensure that the triaxial accelerometer was worn correctly during the measurement period. Therefore, there was no blinding of participants or raters.

As reported previously,^5,6,7) we considered that early postoperative sedentary time influences functional prognosis. Therefore, postoperative sedentary time had to be included in the study. The time required for triaxial accelerometer monitoring is 3–5 days.¹¹⁾ The study period was 72 h from postoperative day 1 to 4 (from the time of the first rehabilitation intervention on postoperative day 1 to the same time on postoperative day 4). This period included at least six sessions of total physical or occupational therapy intervention (generally one session each morning and afternoon for 3 days, for at least 80 min/day) while wearing the triaxial accelerometer.

Physical and occupational therapy intervention times were increased or decreased depending on general conditions, postoperative complications, and medical tests and procedures. The participants were patients in the early postoperative period, many of whom were supervised or assisted when moving (all movements assisted by caregivers were also recorded as physical activity by the participants). Postoperative 3-day medication management for pain was based on regular use of acetaminophen (four times per day) after each meal and before bedtime.

Physical activity in this study was categorized as sedentary time (≤1.5 METs), light-intensity physical activity (1.6–2.9 METs), and moderate-to-vigorous-intensity physical activity (≥3 METs).^10,12) Physical activity was categorized into the following periods: total time, defined as hours per day; awake time, defined as the 15-h period between hospital-determined wake-up (6:00 am) time and lights-out time (9:00 pm) (this was performed to exclude sleeping time); non-therapeutic periods, defined as time awake minus therapy sessions per day; and therapy sessions, defined as the total hours of physical and occupational therapy per day.

Secondary Endpoint

The Mini-Mental State Examination (MMSE)-Japanese scores were obtained from medical records and patients were divided into two groups: cognitive decline (MMSE ≤ 23); no cognitive decline (MMSE ≥ 24).¹³⁾ Surgery type was classified into osteosynthesis and other types (bipolar hip arthroplasty and total hip arthroplasty).

Statistical Analysis

The mean ± standard deviation (SD) and median [interquartile range] were calculated for total time, awake time, non-therapeutic periods, and therapy session physical activity from 4320 min (3 days) of data collected. Subsequently, the percentages of physical activity were calculated relative to the respective postoperative time periods. For physical activity relative to total time, the mean ± SD was divided by 1440 min (total time); for physical activity relative to awake time, the mean ± SD was divided by 900 min (awake time); for physical activity relative to non-therapeutic periods, the mean ± SD was divided by total non-therapeutic periods; and for physical activity relative to therapy sessions, the mean ± SD was divided by total therapy session time. The maximum and minimum values of physical activity were also evaluated. The daily physical activity, classified by each definition (sedentary time, light-intensity physical activity, and moderate-to-vigorous-intensity physical activity), was divided into 60-min segments and then tabulated to analyze daily physical activity patterns.

After performing a Shapiro–Wilk test, the Mann–Whitney U test and chi-square test were used for group comparisons of MMSE score and surgery type. The Mann–Whitney U test was used to compare sedentary time, MMSE scores, and surgery type during the first three postoperative days. Sedentary time in non-therapeutic periods and therapy sessions depended on the total duration of the therapy sessions. Therefore, the total time of non-therapeutic periods and therapy sessions are reported in the results. Sedentary time as a percentage of total time in each period was used for between-group comparisons.

Analyses were performed using SPSS Statistics for Windows, version 25 (IBM, Armonk, NY, USA). The statistical significance level was set at 5%.

No statistical sample size calculations were performed in this study. Therefore, an a posteriori test was conducted using G* power 3.1.9.7 (Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany).^14,15) The sample size was 30, including 23 patients with cognitive decline and 7 patients without cognitive decline. The effect size (d) based on the sedentary time (83.5 ± 9.0% and 70.9 ± 12.4%) during therapy sessions was 1.16. At a two-sided significance level of 5%, the post-hoc power was 0.73.

RESULTS

Participants

This study assessed 107 cases of hip fracture treated at our hospital. Of these, 68 cases were excluded based on the exclusion criteria: 3 patients were aged less than 65 years, 4 were treated conservatively, 29 could not walk independently indoors before the injury, 6 were admitted from outside the home, 6 had high-energy trauma fractures, 1 had a fracture in another part of the body, 2 had motor paralysis caused by pre-existing central nervous system disease, 3 had difficulty with our standard postoperative rehabilitation intervention because of weight-bearing restrictions, and 14 were transferred to another ward. Thirty-nine patients were included in the study, but a further 9 patients were excluded because their triaxial accelerometers were dislodged during the study, leading to incomplete datasets.

Enrollment of new patients was stopped after 30 patients completed 72 h of measurements (Fig. 1). Thirty patients (23 women and 7 men) were included in the analysis, and their mean age was 86.5 years (Table 1).

Fig. 1.

Flowchart of patient participation.

Table 1. Participant characteristics and group comparisons

Characteristic	Total (n=30)	MMSE-based groups			Surgery type-based groups
		MMSE ≤23 (n=23)	MMSE ≥24 (n=7)	P value	Osteosynthesis (n=15)	Other types (n=15)	P value
Age (years)	86.5 ± 5.5	88.0 [85.5–90.5]	84.0 [79.5–84.5]	0.029	89.0 [85.5–92.0]	85.0 [80.5–87.0]	0.029
Sex				0.154			1.000
Female	23 (76.7)	16 (53.3)	7 (23.3)		12 (40.0)	11 (36.7)
Male	7 (23.3)	7 (23.3)	-		3 (10.0)	4 (13.3)
BMI (kg/m2)	20.5 ± 3.0	20.7 [17.6–22.2]	20.0 [19.8–24.5]	0.292	20.6 [19.1–22.2]	21.0 [16.6–23.5]	0.604
Fracture type				0.427			<0.001
Femoral neck	17 (56.7)	12 (40.0)	5 (16.7)		2 (6.7)	15 (50.0)
Trochanteric	13 (43.3)	11 (36.7)	2 (6.7)		13 (43.3)	-
Surgery type				0.182			-
Osteosynthesis	15 (50.0)	12 (40.0)	3 (10.0)		15 (50.0)	-
Bipolar hip arthroplasty	14 (46.7)	11 (36.7)	3 (10.0.)		-	14 (46.7)
Total hip arthroplasty	1 (3.3)	-	1 (3.3)		-	1 (3.3)
Days to surgery (days)	1.5 ± 0.9	2.0 [1.0–2.0]	1.0 [1.0–1.0]	0.013	1.0 [1.0–2.0]	2.0 [1.0–3.0]	0.133
MMSE score	17.8 ± 8.2	18.0 [11.5–20.0]	28.0 [26.0–29.0]	<0.001	19.0 [15.5–21.5]	19.0 [14.0–23.5]	0.934
Therapy time (min/day)	116.0 ± 6.9	116.4 [110.7–121.2]	116.3 [115.3–122.2]	0.523	115.7 [113.0–121.2]	117.0 [107.8–121.8]	0.693

Data are provided as mean ± SD, median [interquartile range] or number (percentage).

BMI, body mass index.

MMSE Score and Surgery Type-based Group Comparisons

MMSE score-based group comparisons showed significant differences in age (P=0.029), days to surgery (P=0.013), and MMSE score (P<0.001). The surgery type-based group comparisons showed significant differences in age (P=0.029) and fracture type (P<0.001) (Table 1).

Sedentary Time and Physical Activity

The mean sedentary time per day was 1364.0 ± 59.9 min/day (94.7% of the day). Light-intensity physical activity had a mean duration of 71.9 ± 57.8 min/day (5.0% of the day), whereas moderate-to-vigorous-intensity physical activity had a mean duration of 4.1 ± 3.2 min/day (0.3% of the day) (Table 2). Sedentary time decreased between 9:00 and 11:00 am and between 2:00 and 4:00 pm. (Fig. 2).

Table 2. Daily time data for sedentary time and physical activity

Activity	Daily time (min/day) a	Mean ± SD (%)	Median [interquartile range]	Range
ST	Total time	1364.0 ± 59.9 (94.7 ± 4.2)	1375.8 [1340.6–1406.6]	1180.1–1425.8
	Awake time	838.6 ± 47.7 (93.2 ± 5.3)	852.7 [824.8–870.1]	680.7–886.8
	Non-therapeutic periods	745.5 ± 38.2 (95.1 ± 4.6)	757.6 [736.3–769.3]	620.1–782.3
	Therapy sessions	93.1 ± 12.1 (80.3 ± 11.1)	96.5 [85.6–101.4]	60.6–108.9
LPA	Total time	71.9 ± 57.8 (5.0 ± 4.0)	57.3 [30.4–93.5]	12.5–244.0
	Awake time	58.2 ± 46.0 (6.5 ± 5.1)	44.1 [28.2–69.8]	11.6–206.4
	Non-therapeutic periods	36.1 ± 34.9 (4.6 ± 4.5)	25.1 [11.7–40.1]	5.7–147.7
	Therapy sessions	22.1 ± 13.0 (19.1 ± 10.8)	21.6 [10.1–28.5]	5.3–58.8
MVPA	Total time	4.1 ± 3.2 (0.3 ± 0.2)	3.1 [2.1–4.8]	0.8–15.9
	Awake time	3.2 ± 2.2 (0.4 ± 0.2)	2.9 [1.9–3.9]	0.8–12.9
	Non-therapeutic periods	2.5 ± 1.7 (0.3 ± 0.2)	2.1 [1.4–3.0]	0.6–9.9
	Therapy sessions	0.8 ± 0.6 (0.7 ± 0.5)	0.7 [0.3–1.1]	0.0–2.9

ST, sedentary time (≤1.5 METs); LPA, light-intensity physical activity (1.6–2.9 METs); MVPA, moderate-to-vigorous-intensity physical activity (≥3.0 METs).

^a Total time, 1440 min; Awake time, 900 min; Non-therapeutic periods, 784.1 ± 6.9 min; Therapy sessions, 115.9 ± 6.9 min; Awake time includes Non-therapeutic periods and Therapy sessions.

Fig. 2.

Daily patterns of physical activity and sedentary time. The sedentary time (ST) was lower during the day from 9:00 to 11:00 am and from 2:00 to 4:00 pm. LPA, light-intensity physical activity; MVPA, moderate-to-vigorous-intensity physical activity.

Association between Cognitive Decline and Sedentary Time

The percentages of sedentary time during total time, awake time, non-therapeutic periods, and during therapy were compared between the cognitive decline group (MMSE ≤ 23) points and the non-cognitve decline group (MMSE ≥ 24). The results for both groups were based on a total daily time of 1440 min and an awake time of 900 min. However, individuals with MMSE score of 23 or lower had a non-therapeutic period of 784.6±7.4 min and therapy sessions of 115.4±7.4 min, whereas individuals with MMSE score of 24 or greater had a non-therapeutic period of 782.5±5.1 min and therapy sessions of 117.5±5.1 min. Comparison of sedentary times showed that patients with cognitive decline had significantly longer sedentary times than those without cognitive decline during total time (MMSE ≤ 23, 96.4%; MMSE ≥ 24, 93.8%; P=0.029), awake time (MMSE ≤ 23, 95.8%; MMSE ≥ 24, 91.8%; P=0.033), non-therapeutic periods (MMSE ≤ 23, 96.9%; MMSE ≥ 24, 94.7%; P=0.042), and therapy sessions (MMSE ≤ 23, 84.5%; MMSE ≥ 24, 72.3%; P=0.015) (Fig. 3).

Fig. 3.

Relationship between sedentary time and MMSE score for total time (1440 min), awake time (900 min), non-therapeutic period (MMSE ≤ 23, 784.6±7.4 min; MMSE ≥ 24, 782.5±5.1 min), and therapy sessions (MMSE ≤ 23, 115.4±7.4 min; MMSE ≥ 24, 117.5±5.1 min).

Association between Surgery Type and Sedentary Time

A comparison of sedentary times between groups based on surgery type revealed no significant differences in sedentary time (Fig. 4).

Fig. 4.

Relationship between sedentary time and surgery type (osteosynthesis or other types) for total time (1440 min), awake time (900 min), non-therapeutic period (osteosynthesis, 782.9±6.2 min; other types, 785.3±7.6 min), and therapy sessions (osteosynthesis, 117.1±6.2 min; other types, 114.7±7.6 min. Other surgery types includes bipolar and total hip arthroplasty.

DISCUSSION

Actuality for Sedentary Time

This study investigated the duration of sedentary time in patients with hip fractures, including those with cognitive decline. Our results showed that the daily sedentary time of patients with hip fractures during the first three postoperative days was 94.7% and sedentary time during awake hours was 93.2%. These results confirmed that patients with hip fractures were mostly sedentary throughout the first three postoperative days. In addition, patterns of physical activity were found to vary by time of day. Cognitive decline affected sedentary time; however, the type of surgery did not affect sedentary time. Further studies should examine the confounding factors for sedentary time.

Relationship between Sedentary Time and Cognitive Decline

Our participants with cognitive decline had longer periods of sedentary time than those without cognitive decline. Many patients with hip fracture are considered to have cognitive decline,⁸⁾ and previous reports that excluded patients with cognitive decline did not reflect the reality of physical activity in this patient population. Therefore, interventions to reduce sedentary time should be reconsidered to account for cognitive decline.

Relationship between Sedentary Time and Surgery Type

There was no difference in sedentary time by surgery type because there was no difference in the content of rehabilitation interventions regardless of the type of surgery. However, the type of fracture and the degree of surgical invasion may have been confounding factors.

Relationship between Sedentary Time and Therapy Sessions

Sedentary time decreased during the morning and afternoon therapy sessions. However, although therapy sessions lasted an average of 115.9 min, sedentary time during therapy sessions still averaged 93.1 min. In other words, sedentary time during a 2-h therapy session decreased by an average of approximately 20 min, which was attributed to the low intensity of the activities performed during the therapy sessions. The patients included in the present study were in the immediate postoperative period, and their activities were limited because of pain, fever, and surgical invasion. Therefore, the sedentary time spent on bedside vital checks, range of motion exercise, and massage may have been prolonged. In addition, time spent on muscle-strengthening exercises of the lower extremities performed while lying down or sitting could have been recorded as sedentary time. Furthermore, immediately after surgery, patients with hip fractures move at a slow speed that could have been construed as low-intensity activity. Of note, this study did not consider behavioral observations, therefore making it impossible to match the exercise intensity of each therapy session with the METs measured by the activity meter. Consequently, it is unclear whether sedentary time in patients with hip fractures reflected actual energy expenditure. We believe that this is a limitation of the methods and measurement equipment used in this study and requires further investigation. However, when compared with the non-therapeutic periods, the duration of sedentary time during therapy was reduced by approximately 12% among patients with cognitive decline and by approximately 22% among patients without cognitive decline. Although rehabilitation by physical and occupational therapists immediately after surgery contributes to a reduction in sedentary time, the amount of medical resources that can be invested is limited. Therefore, we believe that effective measures need to be devised to reduce sedentary time during non-therapeutic periods.

Comparison of Sedentary Times: Present Study and Older Adults Living in the Community

According to a survey of older Japanese adults living in the community, women aged 85 years or older spent approximately 60% of their day in sedentary time.¹⁰⁾ In contrast, the sedentary time in the present study was longer, averaging 93.2%. Given that individuals with a long sedentary times are reported to have an elevated risk of hip fracture,¹⁶⁾ patients with hip fracture possibly had longer sedentary times before injury. In addition, the time of investigation in the present study was immediately after surgery, and activity was limited. However, activity immediately after surgery affects functional prognosis, and we believe that a low target value for sedentary time should be set for the early postoperative period in patients with hip fractures.

Limitations of the Study

In the current study, only 30 patients were included in the analysis, out of 107 eligible patients. Therefore, the study may not have captured the full picture of patients with hip fractures admitted to the hospital. In addition to the small sample size, the comparison groups were not matched for background characteristics, and the examination of associated factors was limited to univariate analysis, meaning that confounding effects may not have been excluded. Finally, the sedentary time measured in this study may have included sleeping time during the day. Therefore, future research should combine behavioral observations with physical activity surveys.

CONCLUSION

This study investigated the duration of sedentary time in the early postoperative period in patients with hip fractures, including those with cognitive decline. The results showed that sedentary time averaged 1364.0 min/day or 94.7% of the day. Cognitive function should be considered when investigating physical activity in patients with hip fractures.

ACKNOWLEDGMENTS

The authors thank the physical and occupational therapists and nurses at Aizawa Hospital for their support in conducting the study.

CONFLICTS OF INTEREST

The authors declare no conflict of interest.

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