A Scoping Review of the Factor Associated with Older Adults’ Mobility Barriers

The phenomenon of ageing may contribute to the rise of the dependent population. Due to the obstacles and difficulties they confront, the elderly’s mobility decreases significantly. The aim of this article is to identify factors associated with mobility barriers in older adults. The method employed is an examination of articles published between 2011 and 2022 to identify common themes in previous studies. Four search engines were being used, and 32 articles have been included. This study demonstrated that health is a major factor associated with decreased mobility. This review identified four types of barriers which are health, built environment, socio-economic background and social relation change. This review could help policy makers and gerontologist in identifying solutions to resolve the mobility issues in older people.


Introduction
The steady increase in older individuals has caused much global concern. Malaysia is projected to encounter the ageing phenomenon by 2030 with an elderly population of 15.3% [1]. Mobility significantly influences older adults' well-being and independence [2] as part of the fundamental needs of ageing [3]. Regardless, the elderly experience a decline in physical and psychological abilities during the ageing process [4]. As such, ageing is associated with low mobility levels, which worsens with disability [5]. Older adults reflect fewer trip frequencies [6,7], reduced travel time [8] and minimal diverse and outdoor activities [9].
Mobility denotes the ability to move across places and outside the home in daily life [10], and select (i) where and when to travel and (ii) which activities to engage in [11]. Older individuals require mobility to fulfil their basic needs. Carp's conceptual model indicates food, clothes, medical services and money as living needs, while socializing, leisure, religious activities and recreation as older adults' additional needs [12]. In this model, mobility is fundamental in determining life-sustaining and additional needs [3]. Both requirements deliver a significant contribution to well-being in later life. Stanley and Lucas indicated mobility as a tool to attain Maslow's hierarchy of needs [13]. In this manner, mobility determines the maintenance needs in life [14] for optimal well-being. The desire for independence, control, status retention, integration, 'normalcy', and travel for its own sake, underpin older people's intention to travel. The relevance of mobility goes beyond accessibility. All these factors influence people's impression of their quality of life [15].
Studies show that, a decrease in outdoor participation among the elderly contributes to loneliness [16]. Loneliness has been identified as a major mental health problem among the elderly, and it can occur when social networks deteriorate [17] due to loss and life changes [18]. Almost half of the elderly in Peninsular Malaysia, specifically urban-area residents, are at risk of isolation [19]. Such loneliness could be exacerbated by low social support, physical disability, and chronic ailments [18]. Older adults must be assisted in coping with loneliness for a high quality of life. Overall, mobility is an effective intervention against isolation and loneliness [15,20], which lowers depression-related risks [21].
The barriers that the elderly face in implementing mobility contribute to their decline in outdoor mobility. Following past works, considerable disparities were identified in outdoor mobility due to the following factors: retirement [22], the ability to drive [23][24][25], having a companion [24], household income [23], and health conditions [23,25]. In line with specific studies, mobility differences were evident between urban and rural areas [26,27], with an emphasis on infrastructure and facilities [28], specifically public transportation [29,30]. Haustein and Siren's literature review from 2000 to 2010, which encompassed the European region, identified the factors differentiating older adults' mobility: health, gender, socio-economic background, car availability, environment, and social networks [31]. Notwithstanding, the distinguishing elements of mobility patterns and behaviours could not be classified under factors associated with mobility barriers. This mobility barrier implies the factors preventing older individuals from achieving the desired mobility and frequency [32].

Research Question
This article focuses on older adults' mobility-oriented barriers and challenges. It is deemed crucial to identify such barriers to resolve these mobility issues. The research question of this review is presented as follows: "What are the factors associated with mobility barriers among older adults?".

Search Strategy and Inclusion Criteria
This scoping review was conducted by screening four electronic databases between 2011 and 2021 through Scopus, Web of Science (WoS), Taylor & France Journal and SAGE, to identify a substantial number of published works. The study was confined to the 2011-2022 range for a broad spectrum of recent research on significant topics. A keyword combination (elder OR older adult AND travel OR mobility AND barrier OR difficulty OR challenges) was sought in titles, abstracts and keywords, to ensure that the article search results fulfil the study purpose based on the screening process criteria. The search was refined in relevant English-language journal categories, such as gerontology, social science, psychology, art and humanity, social work, or transportation. Notably, the records were screened with titles and abstracts to identify relevant articles following the keywords.

Screening
Full-text journals were retrieved and screened to determine the inclusion eligibility. The Preferred Reporting Items for Systematic Reviews (PRISMA) protocol was used to screen these articles [33,34]. The use of PRISMA has several advantages, including the ability to plan in advance, regarding the purpose and form (such as criteria), avoiding duplication, allowing articles to be systematically filtered through predetermined criteria, and enabling other parties or researchers to review, copy, or compare the results protocol [35].
The search strategy generated 6084 searches. A total of 5960 irrelevant articles were removed, while 124 were eligible for full-text reading based on the title or abstract. The eligibility criteria for mobility barriers are presented as follows: (i) research participants must include older adults (>60 years old); (ii) participants' mobility-oriented barriers must be discussed; (iii) research rather than a review study must be conducted. Such criteria were established to ensure that the elicited results significantly demonstrated the key determinants of older adults' mobility barriers. Summarily, 26 articles were selected for data extraction upon being skimmed. Figure 1 depicts the PRISMA process. must include older adults (>60 years old); (ii) participants' mobility-oriented barriers must be discussed; (iii) research rather than a review study must be conducted. Such criteria were established to ensure that the elicited results significantly demonstrated the key determinants of older adults' mobility barriers. Summarily, 26 articles were selected for data extraction upon being skimmed. Figure 1 depicts the PRISMA process.

Data Analysis
Thematic analysis (TA), which enables the systematic evaluation of big data [36,37], was used in this study by generating specific theme patterns, following the researchers' aims. Essentially, TA could clearly depict the similarities and differences between all the study datasets [38]. This analysis also indicates the frequency with which a pattern occurs [38], thus increasing the research accuracy, complexity, and significance. The current study articles were systematically read, with all the statements on older adults' mobility barriers duly coded. Subsequently, the results were analysed by categorising them into multiple sub-themes. Pertinent sub-themes were then merged into specific themes [36].

Results
Eighteen out of the 32 studies were performed in Europe, six in North America, six in Asia, and two in Australia. Various mobility barriers among older adults were identified based on the data extraction outcomes. Two article types were identified: (i) quantitative and (ii) qualitative research. Twenty studies utilised the quantitative method, while 12 employed the qualitative approach. Table 1 depicts the themes derived from TA-based studies. The emergent themes from this review include: (i) health and disability; (ii) build environment; (iii) socio-economic background; (iv) social-relation changes; (v) weather. Table 2 summarises the articles containing the study purpose and their primary outcome.

Data Analysis
Thematic analysis (TA), which enables the systematic evaluation of big data [36,37], was used in this study by generating specific theme patterns, following the researchers' aims. Essentially, TA could clearly depict the similarities and differences between all the study datasets [38]. This analysis also indicates the frequency with which a pattern occurs [38], thus increasing the research accuracy, complexity, and significance. The current study articles were systematically read, with all the statements on older adults' mobility barriers duly coded. Subsequently, the results were analysed by categorising them into multiple sub-themes. Pertinent sub-themes were then merged into specific themes [36].

Results
Eighteen out of the 32 studies were performed in Europe, six in North America, six in Asia, and two in Australia. Various mobility barriers among older adults were identified based on the data extraction outcomes. Two article types were identified: (i) quantitative and (ii) qualitative research. Twenty studies utilised the quantitative method, while 12 employed the qualitative approach. Table 1 depicts the themes derived from TA-based studies. The emergent themes from this review include: (i) health and disability; (ii) build environment; (iii) socio-economic background; (iv) social-relation changes; (v) weather. Table 2 summarises the articles containing the study purpose and their primary outcome.

Build Environment
Housing location is a key determinant of the current state of facilities. Long distances from one's home to the nearest public transportation [46,51,56] and environmental factors (hills, stairs, and parking availability) could discourage elderly people [16,51,52,56,57]. These barriers denote the built environment quality [49]. The availability of local amenities (food stores, newsagents, and post offices) influenced their motivation to venture out. Elderly drivers also complained about poor road structures and were confused about road signs, thus increasing their driving difficulties [58]. Land development might also adversely impact older individuals' mobility. The urbanisation process could alter the original environment [49] and cause elderly individuals to feel less connected to the place.
Seven articles addressed the inconvenience of public transportation for older adults. Most older adults discovered that public transportation is unsuitable for them due to health issues and disabilities. For example, elderly people struggle to board and disembark from public transportation [50] and walk a long distance to the bus stop or train station [42,50,52], following limited access to public transportation [11,52]. Such distances also consume much travelling time [59]. Inconvenient schedules, unsuitable routes, and low frequency discouraged these individuals from using public transportation [50,59,60]. Older users also complained about the discomfort of public transportation shelters, drivers' and other people's behaviour [58], lack of assistance, and unsafe environments [61].

Socio-Economic Background
Wealth, education, and retirement were among the socio-economic aspects highlighted. Older adults with better socio-economic [23,51,62] and educational backgrounds [46] demonstrated high mobility. Retired seniors depicted low mobility [63], as they had fewer reasons to leave the house [41]. This pattern inevitably impacted their spouse [39]. Meanwhile, elderly individuals who lived in affluent neighbourhoods reflected a very high frequency of leisure trips [46]. Thus, income played a pivotal role in perceived health conditions, where higher-income earners observed greater transportation alternatives [47].
Affluence similarly influenced the possession of a vehicle and driver's license. Five articles addressed the impact of owning a car and a driver's license on older adults' mobility. Being a driver and owning a car increased the availability of convenient, comfortable, and optimal [60] elderly transportation resources [42]. In this sense, vehicle ownership significantly affected elderly trip-planning [42,64]. Seniors who could drive themselves reflected a much higher frequency of leisure trips [46], while those who could not depended on family members or friends [56]. The level of unmet needs for out-of-home activities was shaped by transportation-related factors, such as having a driver's license and subjective evaluations of public transportation supply. Actual participation in out-of-home activities, self-perceived health, and walking problems, outlook on life, residential location, and indicators of social support and networks, also explained differences in the extent of unmet activity needs.

Rantakokko et al. 2017 [16] Finland
To perceive the relationship between perceived environmental barriers to outdoor mobility and loneliness among a community-dwelling older people. Linear regression models and logistic regression models Older adults over the age of 75 made fewer total trips, had lesser variety in travel purposes, and travelled shorter distances. Female elderly with medical conditions, who did not drive and had a lower household income tended to make fewer total trips, reflected a lower diversity of trips and travelled a shorter distance.  Physical health issues were the primary reason for quitting driving, which also rendered it impossible to walk or use public transportation. When receiving lifts from family, friends, and neighbours: cars, the element of personal assistance and the accommodation of retired drivers' physical mobility needs were recognised as important factors. Elderly perceived barriers to using active modes, such as walking, cycling, and public transportation, due to mobility limitations or fear of an accident.  Public transportation was an option for the elderly who could not or did not intend to drive, but several barriers or problems discouraged their use.

Social Relation Change
The death of a spouse, relative, or acquaintance might induce loss of companionship and dependability. Eleven articles explored how the loss or absence of a loved one could instigate mobility isolation. The presence of another elderly companion at home demonstrated a significant and positive impact on individual mobility [43,54]. Parallel to past studies, losing a spouse or companion [39,49], or living alone, causes mobility impairment [46,55] and transport deficiency [39]. The absence of an acquaintance may also be caused by the relocation of homes [39]. Being in one place for an extended period strengthens elderly people's social network and support (companion, spouse, family, and friends) and reduces mobility deficiency risks [65]. Older people, particularly women, who generally refrain from travelling alone [66], could seek assistance from their social network or the larger community to travel and participate in outdoor activities [11].

Weather
Only two articles highlighted older adults' difficulties in terms of weather conditions [16,52]. Following Rantakokko, the elderly would limit their outdoor mobility in extreme weather conditions, such as heavy snow [16].

Discussion
Luiu et al. investigated the factors associated with unmet travel needs, which were divided into three categories: health, transportation, and non-transportation [32]. Transportation issues were extensively discussed. Mollenkopf et al., who examined the factors influencing rural and urban elderly mobility behaviours, created a mobility model that identifies personnel resources, socio-economic resources, and structural or regional resources as contributors to outdoor mobility [67]. Regardless, this study classified personnel and socio-economic resources under the same group following their depiction of both individual resources and limitations. From a social ecology perspective, Yeom et al. addressed the intrapersonal, interpersonal, environmental, and organisational risk factors associated with mobility limitations [68]. Based on Yeom et al., interpersonal elements include gender and education level. These factors did not hamper elderly mobility unless they influenced other factors, such as socio-economic status. Thus, the TA outcomes could be divided into two-factor categories: personal (health, social change, and socio-economic background) and environmental (built environment and weather) factors.

Personal Factors
Low elderly mobility primarily results from health issues. Following Alavi, ageing caused physical and emotional changes that are inextricably linked to diseases [69]. An older adult's quality of life is frequently related to health problems, movement difficulties, physical abilities, and sudden emotional shifts. Ageing potentially causes various physical and mental changes and the ability to act and move. These changes could reduce older individuals' well-being. The ageing process constitutes optimal, normal, and pathological ageing [4]. The elderly would inevitably face minimal loss of physical function and health, even in optimal ageing, which worsens with pathological ageing [4]. Ageing, injury, and illness eventually lead to the reduction of or inability to perform specific activities [70].
Low mobility is also caused by poor mental health. Personality changes, mental functioning, and individual sanity indicate psychological ageing [4]. The decline in mental abilities is more complicated than their physical counterparts. Dementia, Alzheimer's disease, and depression are frequently associated with reduced psychological ability. For example, dementia patients often experience depression, anxiety, and confusion, which hampers the performance of daily activities [71].
Older adults grow dependent on their social network owing to poor health and low capacity. Spouses, family members, and friends constitute an elderly person's social network and support. Such networks encourage older adults with limited mobility to engage in activities [72]. Based on the statistics disclosed by the United Nations in 2019, the number of elderly people living alone or with only one partner proved insignificant. In 2010, 27% of the senior population in Asia resided alone or with a spouse [73]. Hamid et al. added that 10% of the 2322 elderly respondents in Peninsular Malaysia lived on their own [74]. These individuals required assistance from the surrounding community or appropriate facilities and services.
In line with Kim et al., education level correlated to income and vehicle ownership, which increased non-home activities [65]. Numerous studies correlated wealth to health status. Highly educated older adults demonstrated better knowledge and cognition, which led to optimal health behaviour and usage of medical services [75]. As such, higher-income earners tended to enjoy better health, independence, a longer lifespan [75], and various transportation options that mitigate outdoor mobility barriers.

Environment Factors
The environment, which significantly affects elderly mobility, could be divided into natural barriers and facilities or structures. Bad weather and hills could be a natural environmental challenge for the elderly to perform outdoor mobility. Facilities and structures involving stairs, poor road lighting, long distance to transportation services [16], and public transportation (buses and trains) are also deemed inconducive for older adults.
Elderly drivers worried about road conditions, insufficient rest areas, curb height, and inadequate lighting [16]. These individuals become confused following the urbanisation process, which inevitably altered the physical environment. Traffic congestion and noise pollution could also make them feel uncomfortable, unsafe, and uneasy. The urbanisation process has caused older people to lose place attachments, such as the emotional bond with the environment that fulfils essential human needs (comfort, happiness, safety, and security) [80] or the emotional man-landscape connection [81].

Recommended Strategies
The aforementioned issues must be resolved, as older adults should not be homebound, regardless of the reasons underlying their low mobility. Changes in their social environment, including family functions [82], social support, social networks, mortality, financial concerns, and chronic diseases, would induce depression [83,84]. The elderly should devise a strategy and expand their resources for mobility task performance. Following Nordbakke's research, individual resources, contextual conditions, and strategies were interconnected in terms of how they expanded mobility capabilities with more development opportunities [56].
The WHO engaged older adults in focus groups to highlight advantages and barriers in eight urban areas worldwide, to create a guideline that encourages age-friendly cities [85]. An age-friendly city alters its structures and services to accommodate older people's needs and abilities and promote active ageing. Thus, the neighbourhood should promote an active lifestyle for elderly adults. Basic mobility facilities, involving pedestrian walkways, elderly-friendly public transportation, proper road lighting, proximity to basic facilities and other associated factors, must also be considered.
Age-friendly cities should include silver industries. Usui explained how Japan encourages senior citizens to live independently. In Japan, the dependent age ratio approach determines older adults' dependence level. The high number, which burdened the Japanese economy, motivated policymakers to address this social complexity. One alternative is the silver industry, which strives to create independent senior persons [83,86]. Such industries create older consumer-based products and services: care centres, activity centres, and private companion services.
Sustainable development goals (SDGs) aim to increase the quality of urban living and age-friendly cities that recommend a safe transportation system for older adults to remain independent and age in place. An intervention through collaborations between public and private transportation companies could establish a new partnership for older adults to enjoy safe mobility for subjective well-being [87]. Simple mobility activities involving shopping, visiting friends, recreation, and eating, also require secure companion services to improve elderly well-being. Although online shopping and food delivery can be directly impactful as an intervention for older people, tech-savvy assistants must be verified to protect elderly individuals from online scammers.
As one of the expanding services in the silver industry, companion services notably improve elderly mobility. A companion provides companionship, practical and emotional support, and improved social networks, confidence, and independence. Resultantly, older adults are encouraged to engage in their local community [88,89]. Transportation becomes easier with the presence of companions, who offer transportation services [90] and introduce the use of public transportation to older adults who are unfamiliar with them [89]. Companionship is also a solution for elderly people without a license or vehicle, or those who have given up driving, live alone, or want to depend less on children or friends. Most elderly people do not prefer to rely on family members or friends [91]. In this sense, companionship presents various beneficial implications and advantages in terms of psychology and lifestyle [88]. This phenomenon implicitly motivates and catalyses elderly mobility. A positive relationship was identified between older people's engagement in physical activities and their overall well-being [15].

Limitation of the Study
This study encountered several limitations. Although the researchers identified some articles on how urbanisation affects low elderly mobility, the topic was not extensively covered. Only several stories emphasised the extent to which well-planned development could facilitate elderly mobility. Future works could extensively discuss these subject areas. Based on the search strategy involving four search engines, none of the studies examined the COVID-19 impact on elderly mobility. Most of the works were also conducted statistically, with the results focusing on mobility patterns and comparison studies, rather than elderly experiences, feelings, and thoughts. Hence, further research should investigate the impacts of urbanisation and the COVID-19 pandemic on elderly mobility.

Conclusions
In line with this scoping review, health issues primarily instigated low mobility and other associated barriers, such as fear of falling, the inability to use public transportation, and the need to be accompanied. Furthermore, the key factors influencing elderly mobility barriers could be divided into two categories: personal (health conditions, social relationships, and socio-economic background) and environment (built environment involving (i) facilities and structures and natural barriers, such as (ii) hills and weather factors). Older adults must undertake relevant measures, such as elderly companion services, to preserve their mobility and well-being. Meanwhile, policymakers should consider the WHO guidelines to develop age-friendly cities and silver industries. The rising number of elderly people must be seriously regarded to prevent negligence or discrimination. Overall, this study supports the SDGs for older adults in the following areas: (i) SDG3: Enable healthy ageing, well-being, and access to health and care services; (ii) SDG11: Build inclusive and accessible cities and communities.

Conflicts of Interest:
The authors declare no conflict of interest.