1. Introduction
As of 2020, the average life expectancy at birth in South Korea was 83.5 years, which is the second highest among all Organization for Economic Co-operation and Development countries [
1]. Continued increases in life expectancy are likely, given the improvements in living environments and advancements in medical technology. However, the disability-free life expectancy, which excludes periods of inactivity owing to disease or injury, is only 66.3 years among South Korean citizens [
1]. The rapid aging of the population and this gap of approximately 17 years may contribute to exponential increases in medical expenses, resulting in a substantial economic burden [
2].
Age-related musculoskeletal physical changes can increase the risk of physical impairment and may lead to poor posture in older adults. Among these changes, decreased range of motion in the knee and hip joints can lead to stiffened movements and altered gait patterns, thereby contributing to balance impairments. Such impairments in balance increase the risk of falling, which is associated with various adverse outcomes, including increased mortality [
3]. In addition to limitations on physical activity, falls contribute to the maintenance of a vicious cycle of progressive instability, further increasing the risk of fall recurrence [
3]. As such, the risk of falling is an important consideration in the management of older adult patients.
Physical fitness parameters such as balance, mobility, and gait pattern are known predictors of fall risk. The Berg Balance Scale (BBS) is an efficient, low-cost, and easily interpreted tool for the functional assessment of fall risk and daily living activities impairment [
4]. As such, numerous studies have utilized the BBS to examine the relationships between fall risk and patient outcomes [
5,
6,
7].
Many instruments have been developed to assess balance and predict falls in older adults. One of the most reliable and valid outcome measures developed today that has been tested in a variety of settings with different populations and diagnoses is BBS [
8]. The BBS has been well established as a valid measure for predicting falls in a variety of patient populations. It has been validated as a predictor of length of hospital stay and discharge destination in stroke rehabilitation [
9,
10] and as a predictor of length of hospital stay and outcomes in acute inpatient rehabilitation when used in conjunction with the functional independence measure [
11]. According to the Park SH study that assessed which tools best predict the risk of falls in the older adults, the BBS showed both pooled sensitivity and a pooled specificity of >0.7. Thus, the BBS was found to be the most useful tool for identifying the older adults with low fall risk [
12]. Given that physical fitness facilitates regular physical activity, adequate functioning in activities of daily living, and healthy aging, such assessments are particularly relevant for older adults.
Age-related changes in cardiorespiratory fitness lead to the structural and functional deterioration of the cardiovascular and respiratory systems, negatively affecting the interactions among various organs and tissues while contributing to physical disability and cognitive impairment [
13,
14]. Progressive decreases in skeletal muscle mass, strength, and physical function caused by aging may lead to sarcopenia, loss of independence, and balance and mobility issues. Furthermore, age-related changes in the collagen structure of connective tissue, increased stiffness in the joints, loss of tissue elasticity, and thickening of the joint tissues significantly reduce the range of motion, thereby leading to decreased flexibility [
15]. These physical fitness deficits also increase the risk of falls, highlighting the need for a thorough investigation of the precise physical fitness parameters associated with fall risk.
In addition to physical fitness parameters, gait patterns, including gait speed under various environmental conditions, may also act as fall risk predictors. Yu et al. [
16] reported that dorsiflexion of the foot when crossing an obstacle could reduce fall risk. An 8-year prospective cohort study investigating whether changes in cognitive performance can predict falls noted that cognitive performance was associated with falling in adults aged >65 years; thus, cognitive performance should be assessed in clinical practice when evaluating fall risk [
17]. In previous studies, various predictors were suggested as potential indicators of fall risk, such as female sex, past falling event, balance impairment, muscle weakness, visual impairment, gait disturbance, depression, and dizziness [
18]. Despite an increased focus on factors that may predict fall risk and aid fall prevention, the evidence to date is insufficient. Therefore, to provide further evidence-based data for the development of safe and effective exercise programs for reducing fall risk, the present study aimed to investigate the associations between fall risk and previous fall events, physical fitness, and gait speeds on flat ground and during obstacle avoidance in older adult women in Korea. In addition, we aimed to analyze the odds ratios for upper and lower physical fitness associated with fall risk in different gait speed groups.
4. Discussion
Agility and dynamic balance issues are the main causes of falls among older adults. Rikli and Jones [
26] reported that agility and dynamic equilibrium are related to gait speed, in turn affecting activities of daily living. Decreases in gait speed and mobility have also been reported as risk factors associated with falls [
5]. Approximately 50% of fall accidents have been reported to occur during tasks that require static and dynamic balance, such as the start and end of gait and rotation in front of a wall [
27]. Neuls et al. [
8] said that it was recommended to check the score of a subject who needs to use a mobile device because of an increased risk of falling.
In this study, the average age of the participants in the lower BBS group was 74.2 ± 5.8 years, that of the participants in the upper BBS group was 71.2 ± 4.9 years, and the participants in the upper BBS group were relatively younger than those in the lower BBS group (
Table 1). Over one-third of adults aged 65 or older and half of those aged 80 years or older commonly experience falls [
3,
28]. The frequency of falls increases with age, and women are at greater risk than men [
29]. De Rekeneire et al. [
30] reported that, among adults aged 70 to 80, 24.1% of women and 18.3% of men experienced a fall within the past year. Liang et al. [
31] reported that 60 (26.1%) of 230 men aged 80 years and older in Taiwan had experienced a fall, while Bath et al. reported a fall rate of 26.4% [
32]. Ribom et al. [
33] reported that, among 3014 Swedish men aged 69–80 years, 16.5% had at least one fall in the previous year, while 7.4% had at least two. The authors further reported that those who had experienced a fall had lower scores for all physical fitness parameters than those who had not. In the current study of older women in Korea, the fall rate was 14.9%, which is slightly lower than the rates reported by Rekeneire et al. [
30], Liang et al. [
31], and Bath et al. [
32] but similar to that reported by Ribom et al. [
33]. These discrepancies may be due to differences in study designs. The relatively low rate reported by Ribom et al. [
33] may be related to the need to obtain measurements over several hours; one-year recall studies may better reflect actual falls than long-term recall studies. Differences in the ages of the included participants may also have contributed to these discrepancies.
Muscle weakness, which leads to decreased physical function and mobility, can lead to falls and fall-related injuries, which can, in turn, increase the risk of mortality. Previous studies have emphasized the importance of fall-related physical fitness in preventing falls [
18]. Lower body muscular fitness is an essential component of physical functioning when standing up from a chair, going up and down stairs, shopping, and traveling in daily life [
34]. Studies have reported that chair-stand test performance is associated with normal age-related functional decline [
35] and fall risk [
36] and can predict fallers and nonfallers [
37]. In this study, lower body muscle strength determined based on the chair stand and timed up-and-go tests was significantly lower in the lower BBS group than in the higher BBS group (
Table 3). Given the rapid aging of the general population and increases in fall incidence, these findings highlight the need for interventions that promote regular physical activity and lower body strength to improve functioning in daily activities and lower the risk of falls among older adults [
38].
Flexibility is an indicator of the ability to perform various activities, such as maintaining correct posture, changing clothes, and walking with a normal gait. In this study, the lower BBS group had significantly lower scores in the chair sit-and-reach test, which measures lower body flexibility (
Table 3). Flexibility refers to the maximal joint range of motion that body tissues can intrinsically achieve without injury [
39]. With age, changes in the musculoskeletal system reduce the joints’ range of motion, resulting in reduced mobility and stride length, which may increase the risk of falls during gait activities. Medical conditions associated with dizziness, such as hypertension, hypotension, or diabetes, have been associated with an increased risk of falls, and this risk can be nine times higher than that in the general older adult population with joint problems or arthritis [
40]. Therefore, activities that improve flexibility, such as stretching exercises and yoga, should be included when designing interventions to mitigate fall risk in older adults.
Degeneration of the musculoskeletal system adversely affects not only the range of motion in the joints but also balance, owing to progressive decreases in physical ability [
41]. In this study, we utilize the timed up-and-go test to assess the speed, agility, and dynamic balance in older adult women. Agility and dynamic balance are essential for safe, smooth movements in daily life, such as getting off the bus, going to the bathroom, answering a phone call, and opening the door. Research has indicated that the fall risk increases as the time required for the timed up-and-go test increases [
42]. As in previous studies, the times in the timed up-and-go test and single-leg stance test for static balance were significantly shorter in the upper BBS group than in the lower BBS group (
Table 3).
A previous study conducted among community-dwelling older adults at high risk for falls reported that a 6-month therapeutically designed Tai Ji Quan balance training intervention was more effective in reducing the incidence of falls than stretching exercise or multicomponent exercise [
43]. Balance can be defined as the ability to control posture. As such, Tai Chi exercises may aid in increasing dynamic balance and muscle strength in the lower body. Indeed, previous studies have reported that various Tai Chi movements can prevent falls in older adults by enhancing not only balance but also proprioception and gait ability [
44]. Chan et al. further reported that men with greater leg and grip strength had a significantly lower risk of falling than those with a relatively lower strength (ORs for highest quartile vs. lowest quartile for relative risk: leg strength, 0.82; grip strength, 0.76) [
45].
In a study that performed logistic regression analysis to confirm the main factors associated with fall risk, participants with times of less than 8.14 s in the 8-foot up-and-go test, an indicator of agility and balance, had ORs for maximum BBS scores that were 11 times higher than those in the reference group. Toraman et al. [
46] reported an average BBS value as high as 54 out of 56 points because they excluded participants who had experienced a fall in an effort to target older adults with good physical functioning. Park et al. analyzed factors that can positively affect functional fitness and mood in independent older adults living in Korea [
47]. The high-risk threshold for the chair stand test for women aged 70–75 was 11 each/30 s. This was lower than the overall average of 14.58 ± 5.04 each/30 s for women in the current study and lower than the average in the lower BBS group (12.75 ± 4.25 s). When the chair stand result is 11 each/30 s or less, independent living can be considered difficult. Further, when the result was 14.58 ± 5.04 each/30 s or more, the OR for the lower BBS group decreased to 0.368, suggesting a relationship between lower extremity muscular fitness and falls. Kang and Lee [
3] reported that the OR for fall events in the low (<30%) vs. medium gait speed (>30%) group was 2.844 (
p < 0.05) on flat ground, indicating an increased risk of falls in the low gait speed group. ORs for the 5 cm obstacle and 30 cm obstacle conditions were 3.585 (
p < 0.05) and 4.877 (
p < 0.01). Thus, as the height of the obstacle increased, the OR for falls in the low gait speed group tended to increase. Kang and Lee also reported that when the analyses for flat ground and obstacle conditions were adjusted for age and body mass index, fall risk rapidly increased as the height of the obstacle increased among individuals with low gait speed [
3].
Ribom et al. [
33] reported that 9.3% of fallers were in the low physical fitness group, defined based on a result ≤3 standard deviations below the mean in the timed chair-stand test, while only 0.3% of nonfallers were in the low physical fitness group (
p < 0.001). The OR for falling in the low physical fitness group was 3.41 (
p < 0.001). In the 20 cm narrow walk test, 13.1% of fallers were in the low physical fitness group versus only 0.1% of nonfallers (
p < 0.001). The OR for falling among those with low physical strength was 2.46 (
p < 0.001). In this study, the ORs for fall risk (BBS) among those with low physical fitness in each test (chair stand, chair sit-and-reach, timed up-and-go, and single-leg stance) ranged from 0.227 to 0.447, with those in the lower gait speed group ranging from 0.327 to 0.605. Thus, the current results support a meaningful relationship between BBS and these fitness indicators (
Table 5 and
Table 6). Nonetheless, further studies are required, given that falls may represent both a cause and consequence of altered physical fitness. Our results suggest that BBS scores above the mean can decrease the ORs for poor balance and flexibility from 0.227 to 0.605, suggesting that the BBS can be used to guide fall prevention strategies.
This study has several limitations, as we only included 148 women aged 65 years or older; thus, first, considering that there are approximately 8.12 million older adults in Korea, the sample size was relatively small. Second, this study was restricted to older adults visiting a senior welfare center located in Asan-si, which limits the generalizability of the results. Third, only the BBS was used to discriminate fall risk levels in the current study, which may have introduced bias. Finally, this study only included women; therefore, future research should include men in a well-designed study on this subject.