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T. Doi1, K. Tsutsumimoto1, K. Makino1, S. Nakakubo1, F. Sakimoto1, S. Matsuda1, H. Shimada1


1. Department of Preventive Gerontology, Center for Gerontology and Social Science, Research Institute, National Center for Geriatrics and Gerontology, Japan

Corresponding Author: Takehiko Doi, Department of Preventive Gerontology, Center for Gerontology and Social Science, Research Institute, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan, TEL & FAX: +81-562-44-5651, E-mail: take-d@ncgg.go.jp

J Frailty Aging 2024;13(2)184-188
Published online February 21, 2024, http://dx.doi.org/10.14283/jfa.2024.17



OBJECTIVES: To examine the association between social frailty and life-space activities, and determine whether a combined status of life-space activities and social frailty is associated with risk of disability among older adults.
DESIGN: A prospective cohort study.
SETTING AND PARTICIPANTS: The participants were 8,301 older adults (mean age 72.9 ± 5.6 years, women [53.3%]) from a community setting.
METHODS: Life-space activities were evaluated using the Active Mobility Index (AMI) to assess activities in each life-space (distance from the respondent’s home: up to 1 km, 1–10 km, or greater than 10 km) during the past 1 month. Activities were also assessed according to physical or social activity. Social frailty and characteristics were measured at the baseline. Incident disability was assessed according to long term care insurance.
RESULTS: The lowest scoring group was based on the quartile in each of the AMI scores (Q1), with reference to the highest scoring group, which had a higher odds ratios for social frailty (AMI total score Q1: OR 4.32, 95% CI 3.43–5.45, AMI physical score Q1: 2.19, 95% CI 1.79–2.69, AMI social score Q1: 5.04, 95% CI 3.94–6.44). During the follow-up (mean 23.5 months), 330 participants had incident disability. Incident disability was associated with social frailty. Combined status of social frailty and low AMI increased the risk of disability (HR 2.15, 95% CI 1.52-3.03), with reference to non-frailty and higher AMI scores.
CONCLUSIONS AND IMPLICATIONS: Social frailty or reduced activity in life-space assessment were identified as risk factors for incident disability. To decrease the risk of disability, the development of an intervention program to enhance activities and cope with social frailty is required.

Key words: Disability, frailty, social interaction, health promotion.



Frailty is a major health problem among older adults that increases the risk of several adverse health outcomes, such as mortality, disability, and hospitalization, owing to a decline in reserve across multiple physiological systems (1, 2). The concept of frailty was developed by recognizing its multidimensional nature, encompassing both physical and psychosocial factors (1, 2). Social frailty is associated with adverse health outcomes, including disability (3-5), mortality (6), and physical frailty (7, 8). According to available guidelines, the management of physical frailty has been demonstrated (9, 10). However, the frailty phenotype focused on social factors is a relatively new concept and requires evidence to understand the best practices to manage social frailty (11). Social frailty was thought to comprise various types of social resources, social behaviors and activities, and self-management abilities, all with the function of adding to the fulfillment of social needs (12).
Whether activity engagement is related to social frailty remains a major concern. Physical activity has been recognized as an appropriate intervention for managing physical frailty. However, there is no consensus regarding the association between physical activity and social frailty. In fact, maintaining or increasing physical activity is related to a decreased risk of social frailty (13), whereas physical inactivity as a component of physical frailty is not associated with social frailty (14). Furthermore, life-space mobility and activity measurements based on lifestyle are not associated with social frailty (8). The discrepancy among these studies is partly due to the disconnection between life-space mobility and physical activity. Life-space mobility and physical activity are inseparable, and there is a need to view both comprehensively and examine their association with social frailty and incident disabilities among older adults. However, whether activity enhancement contributes to a decreased risk of disability based on social frailty remains unclear. Understanding the association between social frailty and engagement in activities and the role of the association in the risk of disability can help in the development of preventive strategies for disability through the management of social frailty. This study investigated the association between social frailty and physical and social activities according to life-space using the Active Mobility Index (AMI) (15, 16). We also examined whether the combined status of increased life-space activities and social frailty is associated with incident disabilities.




The eligible participants were 8924 older adults aged 65 years and above from the National Center for Geriatrics and Gerontology—Study of Geriatric Syndromes (NCGG-SGS),, whose detailed information has been described elsewhere (17). We then used the following exclusion criteria to further filter out participants: 1) being certified by long term care insurance (LTCI), 2) history of dementia or Parkinson’s disease, 3) severe cognitive impairment (Mini-Mental State Examination < 20) (18), and 4) missing values in our assessment. Disability incidence, as certified by LTCI, was regarded as the main outcome. Thus, participants who were certified by LTCI at the baseline were excluded. In addition, those with factors having direct effects on incident disability, such as severe cognitive impairment and neurological disorders, were also excluded. Finally, 8,301 people (mean age 72.9 ± 5.6 years, women [53.3%]) were analyzed. Among the participants, 15 used a cane as a walking aid. Informed consent was obtained from all participants before their inclusion in the study, and the study protocol was approved by the relevant institutional ethics board of the National Center for Geriatrics and Gerontology.


Active Mobility Index

The AMI assessed life-space activities within the physical and social domains using detailed protocols outlined in previous studies; with its predictivity for disability and concurrent validity that has been validated by previous studies (15, 16). The AMI was also validated using objectively measured physical activity (19). The AMI evaluated activities within the past month across three distinct life-space levels: up to 1 km from the participant’s residence, 1–10 km, and >10 km. Participants were also asked about their activity frequency, purpose, type of transportation, and the extent of interaction with others and their physical activity. Life-space scores were calculated for each level by multiplying the life-space level score (up to 1 km: = 1 point; 1–10 km = 2 points; >10 km = 3 points) with the frequency score (< once = 1 point; 1-3 days = 2 points; 4-6 days = 3 points; everyday = 4 points). In addition, physical and social scores were computed by multiplying the life-space scores with the sum of the scores of the outdoor activities (purpose, transportation, extent of physical activity, and extent of interaction with others). After calculating the life-space, physical, and social scores, the scores for each level were aggregated. The total score ranged from 0 to 216, with higher scores representing increased mobility during activities.

Social frailty

Social frailty was evaluated according to an established definition elaborated upon in previous studies (5, 20). The definition included daily social activity, social role, and social relationships, and it was validated in a previous study (5, 20). The evaluation encompassed five distinct elements: going out less frequently compared to the preceding year (applicable response: yes), visiting friends occasionally (applicable response: no), perceiving oneself to be helpful to friends or family (applicable response: no), living alone (applicable response: yes), and talking with someone every day (applicable response: no). Social frailty status was defined according to the number of applicable responses: no social frailty (0–1) and social frailty (≥ 2).

Other measurements

Data regarding medical conditions, chronic diseases (hypertension, hyperlipidemia, and diabetes), and number of medications were obtained through interviews. The demographic data collected include age, gender, and educational history. Physical activity habits, depressive symptoms, and cognitive functioning were also assessed. Depressive symptoms were measured using the 15-item Geriatric Depression Scale (GDS) and scored (0 to 15) (21). Cognitive functioning was assessed using the Mini-Mental State Examination (MMSE) (18).


Incident disability was ascertained through recorded data from the LTCI and was characterized by any level of required care or support certification (support level 1 or 2: a need for assistance to support activities of daily living; care levels 1 through 5: a need for continuous care (22). LTCI was designed as a national insurance system in Japan, and the process of certification in LTCI has been described in detail elsewhere (22). In summary, a trained local government official performed home visits to evaluate support and care needs using a questionnaire on current physical and mental status (73 items) and use of medical procedures (12 items). Based on the results, standardized scores were calculated for seven dimensions of physical and mental status, and the time required for the categories of care (grooming/bathing, eating, toileting, transferring, assistance with instrumental activities of daily living, behavioral problems, rehabilitation, and medical services) was determined. The assigned care-needs level was based on the total estimated care minutes. A Nursing Care Needs Certification Board, which comprises experts in health and social services appointed by a mayor, determines whether the initial assessment is appropriate, based on the applicant’s primary care, physician’s statement, and assessor’s notes collected during the home visit. The board then makes a final decision on certification in LTCI. In this study, disability was defined as a new certification of LTCI service at any level. Recorded data of LTCI were updated monthly during the follow-up (mean ± SD: 23.5 ± 2.7 months). In case of death or relocation, the event was censored.

Statistical analyses

Baseline data, including AMI scores, were summarized based on social frailty status. To test the cross-sectional association between social frailty and AMI, logistic regression analysis was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs). Social frailty (no social frailty versus social frailty) was set as an objective variable. Each AMI score (total score, physical score, and social score) was set as an explanatory variable and was categorized based on quartiles (Q1: lowest, Q4: highest). The logistic analyses were adjusted for confounders, including age, sex, chronic diseases, medication use, educational history, depressive symptoms (GDS > 5 or others), and cognitive impairment (MMSE < 24 or others). The confounders were selected based on prior research and domain knowledge.
Next, Cox proportional hazard regression models were used to calculate the hazard ratios (HRs) with 95% CIs for incident disability. To test whether social frailty and AMI were independently associated with disability, AMI scores based on both quartiles (Q1: lowest, Q4: highest) and social frailty were set as explanatory variables, and we adjusted for confounders used in the logistic analyses (age, gender, chronic diseases, medication use, educational history, depressive symptoms, and cognitive impairment). In addition, to determine whether a combined status of AMI (high or low) and social frailty (no frailty or frailty) is associated with disability, the combined status was set as the explanatory variable. These analyses were also adjusted for confounders used in the logistic analyses. Statistical analyses were conducted using SPSS version 28.0 (IBM Corp., NY, USA), with statistical significance set at P < .05.



The participants’ characteristics are summarized in Table 1. Overall, the mean age was 72.9 ± 5.6 years and the proportion of female participants was 53.3% (n = 4426). The proportion of participants with social frailty was 15.1% (n = 1092). The participants’ mean AMI score was 72.1 ± 29.2, the mean AMI physical score was 31.8 ± 17.1, and the mean AMI social score was 40.3 ± 18.6. To examine the association between AMI and social frailty, the quartile of each AMI score was used (AMI total score Q1: ≤ 52, Q2: 53 to 70, Q3: 71 to 90 Q4: ≥ 91; AMI physical score Q1: ≤ 20, Q2: 21 to 30, Q3: 31 to 42 Q4: ≥ 43; AMI social score Q1: ≤ 27, Q2: 28 to 38, Q3: 39 to 52 Q4: ≥ 53). A logistic regression indicated an association between AMI and social frailty, as shown in Figure 1 (all p-values for trends were < .001). The lowest scoring group in each of the AMI scores (Q1) had higher odds ratios for social frailty (AMI total score Q1: OR 4.32, 95% CI 3.43–5.45, AMI physical score Q1: 2.19, 95% CI 1.79–2.69, AMI social score Q1: 5.04, 95% CI 3.94–6.44).

Table 1. Participants’ characteristics

Note: AMI, Active Mobility Index; GDS, Geriatric Depression Scale; MMSE, Mini-Mental State Examination.

Figure 1. Results of logistic regression analysis to examine the association between social frailty and AMI

The odds ratios for each AMI quartile were estimated with 95% confidence intervals (CIs). AMI, Active mobility index; OR, odds ratio; CI, confidence interval.


During the follow-up period (mean 23.5 months), participants with incident disability were 330, and those with censoring data were 130 (death: 81; relocation: 49). To examine the association between social frailty, AMI, and incident disability, HRs were calculated using a Cox proportional hazards model (Table 2). Social frailty and AMI were associated with incident disability (Model 1: social frailty; HR 1.48, 95% CI 1.14-1.92; Model 2: AMI total score Q1; HR 1.61, 95% CI 1.15-2.26, p value for trend = < .001). Model 3, including social frailty and AMI simultaneously, showed similar results (social frailty: HR 1.37, 95% CI 1.05-1.78; AMI total score Q1: HR 1.52, 95% CI 1.08-2.14, p value for trend = .018). The association between disability and the combined status based on social frailty and AMI (high or low) was also examined (Table 3).

Table 2. Association between social frailty, active mobility index, and incident disability using Cox proportional hazard model

Note: To examine the association of social frailty and Active Mobility Index with incident disability, Cox proportional hazard ratios were calculated. Model 1 set social frailty and covariates as explanatory variables, and Model 2 set Active Mobility Index total score based on quartile (Q1: ≤ 52, Q2: 53 to 70, Q3: 71 to 90 Q4: ≥ 91). Model 3 included both social frailty and the Active Mobility Index quartile with covariates. HR, hazard ratio

Table 3. Hazard ratios for incident disability among combined status based on status of social frailty and active mobility index

Note: Groups were defined by combined status based on the relationship between social frailty and Active Mobility Index. High AMI was defined as more than the median value of the AMI total score, and low AMI was defined as other values. The HRs of the groups were calculated and referred to as groups (no frailty and high AMI). HR, hazard ratio; AMI, Active Mobility Index



Our study revealed an association between social frailty and fewer life-space activities, as demonstrated by a low AMI score. Both social frailty and decreased AMI were independently associated with a risk of incident disability during the 2-year follow-up period. The combined status of social frailty and low AMI was associated with a higher hazard ratio for disability. These results remained in the models adjusted for confounders.
Social frailty was associated with fewer life-space activities, represented by a decrease not only in the total score of AMI but also in the sub scores of AMI (physical and social scores). The AMI assesses life-space-related activities, including physical and social activities (15, 16). The finding that low engagement in social activity is related to social frailty is reasonable owing to the origin of social frailty (23), and the physical score of the AMI was also associated with social frailty, thereby adding to our knowledge regarding social frailty. Pek et al. indicated that social frailty is associated with decreased physical activity but not life-space mobility, as represented by life-space assessment 8. Owing to the different definitions of social frailty and the characteristics of participants across studies, the results may differ. Our study defined social frailty based on five components, whereas Pek et al.’s study defined social frailty based on nine components 8. In addition, our study had a larger sample size with a higher age, proportion of men, and educational history compared to Pek et al.’s study (8). Our study adds to the literature regarding the association between social frailty and life-space-related activities.
Social frailty and AMI were independently associated with disability, even when these variables were set in the same model. In turn, the pathway through which disability develops from social frailty does not necessarily coincide with that of reduced life-space mobility or activities. Several cohort studies have revealed that social frailty is associated with an increased risk of disability according to the status of social frailty (3-5), although the definition of social frailty varied among the studies. In contrast, a previous study with different samples and follow-up durations showed that a low AMI was associated with disability (15). Although the follow-up duration in this study was relatively short, similar results were obtained. Our findings are in line with these studies on social frailty and AMI.
In addition, the maintenance of AMI moderated the role of social frailty in the risk of disability. Engagement in activities could be useful as a preventive approach to disability through social frailty. AMI scores are associated with objectively measured physical activity, and high AMI scores are related to more daily steps and longer periods of moderate-to-vigorously intense physical activity (19). Maintaining or increasing the frequency of physical activity improves overall physical, psychological, and social frailty (13). On the contrary, social isolation and loneliness was related to the progression of frailty (24, 25), and social frailty preceded the development of physical frailty (7). Thus, early approaches for the prevention of social frailty may play a key role in modifying the course of physical frailty to disability. The development of interventions for social frailty, e.g., enhancing social interaction to use information and communication technology, is also required.
Our study has several strengths and limitations. A prospective study design with a large sample is a major strength. Incident disabilities during the follow-up period were covered by the national insurance system. However, a detailed cause of disability could not be determined (e.g., physical disability or cognitive disability). In addition, the participants in our study responded to information on the invitation to participate in the survey. The participants’ potential interest in health may have resulted in selection bias. Thus, the results of this study cannot be generalizable to all older adults. Furthermore, this study’s exclusion criteria potentially limit the applicability of the findings to a broader population. Additionally, the current results do not indicate a causal association with disability. Functional decline due to disabilities affecting AMI or social frailty is a possible reverse causation. However, further studies are required to address these limitations.


Conclusion and Implications

This study showed that social frailty or low activity according to life-space is a risk factor for incident disabilities. Further studies are required to develop an intervention for preventing disability, focused on enhancing activity, and to validate its effects among older adults with social frailty.


Funding: This work was supported by the Research Project on Health and Welfare Promotion for the Elderly from the Japan Agency for Medical Research and Development (grant numbers: 15dk0107003h0003, 15dk0207004h0203, 18dk0110021h0003), JSPS KAKENHI Grant Number 22H03462 and by Research Funding for Longevity Sciences (grant numbers 26-33) from the National Center for Geriatrics.

Conflict of Interest: None.

Ethical standards: The ethics committee of the National Center for Geriatrics and Gerontology approved the study.



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