Introduction

Forty percent of older adults, approximately 17.6 million people in the U.S., are unable to walk ¼ mile (0.4 km) or climb stairs independently [1]. Mobility limitations progress over time, and with increasing age, leading to functional decline and disability in activities of daily living (ADLs) and instrumental activities of daily living (IADLs) [2,3,4]. This number is expected to rise as the aging population increases in the near term [5]. Known risk factors for the development of mobility limitations include underlying strength and balance impairments, previous hospitalizations, chronic disease, obesity, and decreased physical activity [2,3,4, 6,7,8,9,10]. Widespread pain, depression, and cognitive impairment are also associated with onset or worsening of mobility limitations in this age group [3, 7, 11, 12].

Alterations in mobility patterns result in adverse outcomes that affect the physical, psychological, and social domains of life for older adults [13]. Those with mobility limitations are at risk for social isolation [14], increased healthcare utilization, increased occurrence of falls, and decreased quality of life [1, 11, 15]. Fear of falling is a common outcome of mobility limitations in older adults and results in activity avoidance, further interfering with mobility [16]. Fear of falling increases with age and is more prevalent in women than men [17]. When mobility limitations are present along with fear of falling, the risk for a future fall increases substantially [18]. Among community-dwelling older adults who report fear of falling, health-related quality of life also deteriorates [19, 20]. A better understanding of the symptoms responsible for the mobility difficulties may provide an area for clinical management that could improve mobility.

Symptoms, or the subjective multidimensional experience of a physical disturbance [21], are frequently reported by older adults as burdensome and are a primary reason for seeking healthcare [22,23,24,25]. Symptoms rather than a particular chronic disease have been more readily identified by older adults as causing mobility difficulty [23]. In a large, nationally representative sample of community-dwelling older adults in the United States (U.S.), almost half reported two or more symptoms that were difficult to manage [26]. Among disabled older women, unsteadiness, hip pain, knee pain, and weakness were symptoms frequently reported as directly responsible for their difficulty walking and climbing stairs [23].

Although older adults often experience multiple symptoms that contribute to changes in mobility patterns, interfere with daily activities, and are an underlying cause of disability [23, 27], the focus of research to date has not identified the relationship between self-reported symptoms specifically responsible for mobility difficulties and the resulting adverse outcomes such as fear of falling. Symptoms may be treatable; a focus on self-reported symptoms related to mobility difficulties versus disease pathology that is less modifiable may be a more manageable task and more likely to lead to improved functioning in older adults [23, 28]. The aims of the current study were to identify the prevalence of the most commonly reported symptoms that are the main causes of mobility difficulties and to determine which types of self-reported disabling symptoms (i.e., pain, balance, weakness, endurance, other) are associated with the greatest fear of falling. We hypothesized that pain would be the most prevalent symptom category identified as the primary cause of mobility difficulty. We also hypothesized that balance symptoms causing mobility difficulty would be most strongly associated with fear of falling, compared to other types of symptoms.

Methods

A secondary data analysis was performed using cross-sectional baseline data from the population-based cohort study of community-dwelling older adults, the “Maintenance of Balance, Independent Living, Intellect and Zest in the Elderly of Boston,” known as the MOBILIZE Boston Study (MBS). MBS examined novel risk factors for falls in cognitively intact older adults living in Boston and surrounding suburbs, enrolling participants between 2005 and 2008 [29]. Details regarding the study design and baseline measures have been published previously [29]. Participants were recruited door-to-door in a random sample of older adults living in a defined geographic area within 5 miles (8 km) of the study clinic in Boston. Participants who met the following criteria were enrolled in the MBS study: (1) aged ≥ 70 years, (2) communicates in English, (3) plans to stay in the Boston area for 2 years, and (3) able to walk 20 feet (6 m) without personal assistance [29]. Otherwise, eligible domestic partners aged 65 and older of enrolled participants were also allowed to join the study. Screenees were excluded for: history of terminal disease, severe hearing or vision deficits, or moderate or severe cognitive impairment (Mini-Mental State Examination score < 18). A total of 1616 adults met eligibility. After further screening in the study clinic, 765 older adults with a mean age of 77.9 (± 5.5) years were enrolled into the baseline MBS study with a response rate of 53% among the eligible sample [29, 30]. Informed consent was received from each participant after confirmation of eligibility. Data collection occurred during a two-part assessment, which included a home interview followed within 4 weeks by a clinic examination [29]. Human subjects approval for this study was obtained from the Institutional Review Board of the home institution of the primary author (MAM).

Subjects

Of the 765 older adults enrolled in the MBS at baseline, 242 participants reported difficulty walking ¼ mile (0.4 km), climbing a flight of stairs, or both and were included in the analysis. As a subset of the MBS cohort, our study sample is representative of the older adult population with mobility difficulty living in the community. It is estimated that 40% of older adults living in the community are unable to walk a ¼ mile (0.4 km) or climb stairs independently [1].

Instruments

Mobility was measured via a health interview initially using two questions [29]. The first question asked whether the participant had difficulty walking ¼ mile (0.4 km); the second question asked about any difficulty climbing a flight of ten stairs [31]. Participants who reported difficulty for either item were asked to report how difficult it was to perform the activity with response options of, ‘a little difficulty’, ‘some difficulty’, ‘a lot of difficulty’, or ‘unable to do’ [2]. In addition, they were asked about the main symptom responsible for each reported mobility difficulty. The participant was asked to identify the main symptom causing their walking or stair-climbing difficulty, referring to a list of 32 common symptoms that contribute to mobility difficulty based on our work and the work of others, grouped according to five categories: pain, weakness, balance, endurance, and other symptoms (Table 1) [2, 23, 27]. In a previous report, the self-reported symptom causes of disability were associated with objective measures of mobility performance including leg strength, standing balance, and gait [27].

Table 1 Symptoms list
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The pain category included any reports of pain or stiffness in a joint, general body pain, chest pain or other arthritis problems. Weakness included numbness, weakness, decreased sensation, tremors, or paralysis in extremities. Fatigue and shortness of breath are categorized as endurance. Fear of falling, unsteadiness, or dizziness are included under the umbrella of balance. Participants who reported fear of falling as a symptom were removed from the analysis for the second hypothesis. Symptoms listed as other include incontinence, confusion, obesity, anxiety, or any other problem that did not fit into a specific category.

The Tinetti Falls Efficacy Scale (FES) is a valid and reliable tool used to measure fear of falling, defined as low perceived self-efficacy while completing activities of daily living [32]. The 10-item instrument assesses the confidence the participant has in completing everyday activities without falling on a scale from 1 to 10 with 1 denoting ‘not confident at all’ and 10 representing ‘extreme confidence’. Activities included are bathing, reaching into cabinets, preparing meals, getting in and out of bed and in and out of a chair, answering the door or telephone, walking around the house, getting dressed, performing light housekeeping, and simple shopping tasks. Scores are reported as a total summed score from 10 to 100 with higher scores indicating higher confidence and lower fear of falling.

Data analysis

Data were analyzed with SPSS (Version 25.0, Armonk, NY: IBM Corp.). Descriptive statistics were used to characterize the study sample. Means with standard deviations were used to describe continuous data; categorical data were described using frequencies and proportions. The sample includes those who identify having any difficulty with walking, stair climbing, or both activities. The final sample for analysis included 242 participants. ANCOVA was used to determine differences in associations between symptom categories and fear of falling adjusting for gender, race, education, vision, BMI, and mobility difficulty (a binary variable denoting whether the participant had problems with both walking and stair climbing or just one of the measures). After checking interaction effects between symptom categories and factor variables, such as gender (none of which were statistically significant), it was decided to use a model with only main effects due to the limited sample size and to maintain parsimony.

Results

The sample consisted of 242 older adults with a mean age of 79.35 (± 5.65) years who reported difficulty walking ¼ mile (0.4 km) and/or climbing one flight of stairs (Table 2). Those reporting balance symptoms were the oldest participants (mean age = 83.7 ± 5.04) and significantly older than participants in all categories except the weakness category. Although there were only minor differences in prevalence of symptoms according to gender, white participants had lower prevalence of endurance symptoms and higher prevalence of weakness symptoms compared to Black participants. There were no statistical differences between groups on race, gender, or education. The most common self-reported symptom category among participants was pain, affecting 38% (n = 93) of participants, followed by endurance (n = 51; 21%), weakness (n = 32, 13.2%), and balance (n = 21; 8.6%) (Fig. 1). There were 38 (15.6%) participants who reported discordant symptoms, or a different symptom category for walking as compared to stair climbing and seven (3%) whose symptoms were included in the “other” category. Among the small group of participants with discordant symptoms, pain was the primary cause of difficulty walking (n = 15; 38%) and weakness, the primary symptom category for difficulty climbing stairs (n = 11; 29%).

Table 2 Prevalence of reported symptoms causes of mobility difficulty, according to characteristics of study population, 242 adults aged 70 and older with mobility difficulty, MOBILIZE Boston Study, 2005–2008
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Fig. 1
figure 1

Prevalence of types of main symptom causes of mobility difficulty

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For participants who reported difficulty walking ¼ mile (0.4 km), 16% (n = 30) had a little difficulty, over 50% reported some difficulty (37%, n = 70) or a lot of difficulty (32.3%, n = 61) while 14.8% (n = 28) were unable to complete the activity at all. Sixteen (10.1%) participants were unable to climb stairs; 21.4% (n = 34) had a little difficulty while 44% (n = 70) had some difficulty and 24.5% (n = 39) reported a lot of difficulty with stair climbing.

Fear of falling was reported by 30% (n = 73) of participants (Fig. 2). According to symptom categories, the highest percentage experiencing fear of falling were participants who reported balance-related symptoms (55%; n = 12). In the other symptom categories, approximately 26% of those reporting pain (n = 24), one-third of participants reporting endurance (n = 16), and 22% (n = 10) with discordant or other symptoms had fear of falling (Fig. 2). In pairwise comparisons for symptom category, those who identified balance as their primary symptom had higher fear of falling than those identifying endurance (p = 0.005), pain (p = 0.001), or discordant (p = 0.001) symptoms. There were no differences in fear of falling for older adults identifying balance compared to weakness as the primary symptom causing mobility difficulty (p = 0.106).

Fig. 2
figure 2

Prevalence of fear of falling according to symptom category

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Discussion

As hypothesized, our findings showed that pain was the most prevalent reported symptom cause of mobility difficulty in community-dwelling older adults. These findings build on a previous study of disabled older women who reported hip and knee pain as primary symptoms responsible for difficulty walking and climbing stairs [23]. In a study of 4661 older adults, pain interference was one of the strongest predictors of moderate and severe mobility limitations [11].

Although pain affects over 50% of older adults in the United States, pain management is often less than optimal in this population [33]. Biases from healthcare providers, concern for medication overdose or misuse, and the presence of co-occurring comorbid conditions can make it challenging to implement effective pain treatment plans [34]. Lack of a clear diagnosis for the underlying causes of pain can also contribute to undertreatment. Nonetheless, our findings show that pain as a symptom, regardless of the cause, is the leading contributor to mobility difficulty in older adults. When pain is undertreated, older adults are at increased risk for disability, social isolation, and greater healthcare costs [12, 34, 35], while appropriate pain management improves quality of life, and decreases risk for the associated adverse outcomes [36, 37].

Endurance-related symptoms, including fatigue and shortness of breath are the second most reported symptom category contributing to difficulty walking or climbing stairs. In the Baltimore Longitudinal Study of Aging (BLSA), older adults with fatigue experienced a significant decline in functional performance including gait speed and walkability over a 2-year period [38]. Data from the Women’s Health and Aging Study showed that fatigue and shortness of breath were reported by one in four disabled older women as the primary reasons for difficulty walking a ¼ mile (0.4 km) [23].

Among the discordant subgroup in our study, although pain was the primary symptom associated with difficulty walking, weakness was the symptom most often reported as the main cause of difficulty climbing stairs. Older adults may have multiple symptoms that affect functioning and limit the ability to move about effectively [23, 27]. Based on our results, pain and weakness symptoms may be related, and further research should be conducted to evaluate this possible relationship. Depending on the task, the main symptoms reported by the older adult may vary in the same person, but we did not evaluate relationships between the symptoms. Therefore, a better understanding of the impact of multiple disabling symptoms is key for developing effective disability prevention strategies for aging adults.

As hypothesized, balance was significantly associated with fear of falling compared to most other types of symptoms. Others have shown that difficulty with balance is associated with the fear of falling in older adults and that fear of falling is a major risk factor for falls and disability [39, 40]. Therefore, it is no surprise that those who self-report balance symptoms as the main cause of their mobility difficulty experience more fear of falling than others. However, the relationship between self-reported pain causes of mobility difficulty and fear of falling cannot be discounted. Compared to balance symptoms, pain was reported by more older adults as causing mobility difficulty and thus was associated with a higher population burden of fear of falling. These results are consistent with a previous systematic review reporting that older adults with pain have increased concerns or fear related to falling [41].

The importance of self-report for this research cannot be understated. Self-reported symptoms are key to understanding mobility problems that an older adult may be experiencing [27]. This study included symptoms that older adults deem responsible for their mobility difficulty. Symptom burden is common in the older adult population and not always directly associated with a comorbid condition [23]. When symptoms are the result of a comorbid condition, treatment may focus on the disease process versus targeted symptom management. When symptoms are not linked to a diagnosed disease, the symptoms may be discounted by the older adult, caregivers, and healthcare providers as a consequence of aging and the true risk for daily functioning may not be recognized. A number of studies have found that symptom burden is associated with decreased physical performance, increased health care utilization, and decreased quality of life in older adults [17, 25, 26, 41,42,43]. Further research is necessary to determine if using a symptom-based treatment approach regardless of comorbidity status can improve quality of life and reduce the risk for adverse outcomes like fear of falling, the progression of mobility decline, and falls.

This study lends a novel approach to investigating mobility issues and fear of falling among older adults but is not without limitations. Participants were required to select the main symptom cause for their difficulty walking or climbing stairs. It is possible there were multiple symptoms present; therefore, further research on the associated burden of symptoms is necessary. Fear of falling was included on the list of symptoms and was reported by 20 (10%) participants, and subsequently, they were removed from the analysis for the second aim. Overall, our study had a modest sample size; future studies with larger samples are warranted to further define the role of symptoms as contributors to disability and fear of falling.

Despite these limitations, the results of this study underscore the importance of patient self-report and the recognition of the symptoms as causes of mobility problems including an associated fear of falling. The current study was conducted with a population-based cohort of older adults; therefore, the results are generalizable to other community-living older populations. Future studies focused on the self-reported symptoms associated with disability and other common adverse outcomes including quality of life and falls are needed. The development of a symptom profile or clusters of symptoms may assist in understanding who is at highest risk for mobility difficulty and associated adverse outcomes. A symptom profile could guide the development of tailored interventions for symptom management, mobility improvement and disability prevention. It is possible that interventions solely focused on functional loss may be less effective when symptom burden is not addressed. Further research on the symptom burden experience and the relationship with function and disability is warranted.