Abstract
Objective
To study the extent to which fear of falling (FOF) is associated with the onset of functional disability over a 2-year period in older adults using self-reported and performance-based measures.
Methods
In 2012, 1,601 participants (aged 65–74 years) were recruited from four sites: Kingston and Saint-Hyacinthe, Canada; Manizales, Colombia; and Natal, Brazil. They were re-assessed in 2014. We quantified FOF using the Fall Efficacy Scale-International (FES-I; range: 16–64). Functional disability measures were (i) self-reported incident mobility disability, defined as difficulty climbing a flight of stairs or walking 400 m and (ii) incident poor physical performance, defined as a score <9 on the Short Physical Performance Battery. In the Poisson regression analysis, we included only those participants without functional disability at baseline to calculate incident risk ratios in 2014.
Results
1,355 participants completed the 2014 assessment, of which 917 and 1,078 had no mobility disability and poor physical performance at baseline, respectively. In 2014, 131 (14.3%), and 166 (15.4%) participants reported incident mobility disability and poor physical performance, respectively. After adjusting for age, sex, socioeconomic, and health covariates, a one-point increase in FES-I at baseline was significantly associated with a 4% increase in the risk of reporting incident mobility disability (95% CI: 1.02–1.05) and a 3% increase in the risk of developing poor physical performance at follow up in the overall sample (95%CI: 1.01–1.05).
Conclusions
FOF is associated with a higher risk of incident mobility disability and poor physical performance in a cohort of older adults. It is increasingly important to study FOF’s effect on functional disability and to take necessary measures to prevent the transition to end-stage disability.
Keywords: Longitudinal, Functional decline, Falls-efficacy, Functional limitation
Fear of falling (FOF) is an important psychological factor that has been associated with an array of adverse outcomes in older adults including decreased muscle strength and physical capacity, social isolation, falls, greater frailty, decline in mobility, higher risk of disability in daily living activities, and increased mortality (1–4). While it is commonly a result of a previous fall, FOF is also common in older adults who never experienced a fall. Among those who never experienced a previous fall, FOF was shown to be the most important factor in predicting future falls (5).
Several cross-sectional studies have identified a relationship between FOF and functional decline, but these studies were limited by their inability to demonstrate that FOF precedes this decline (2). Additionally, few longitudinal studies found a relationship between FOF and functional decline (6–9). These studies in general focused on testing the relationship between FOF and decline in self-reported instrumental and basic activities of daily living (IADL and ADL). Previous research showed that the association with FOF was stronger for self-reported than performance-based outcome measures of functioning (10); thus, it is important to include both types of measures in such studies as the association with them might be different. To our knowledge, no previous studies investigated the relationship between FOF and incident functional disability over time using both self-reported and performance-based measures. Moreover, available studies focused on one geographic location, which prevented researchers from examining the full range of their variables of interest.
The objective of this study was to examine the extent to which FOF is associated with incident functional disability over a 2-year period in older adults using self-reported and performance-based measures. We hypothesized that FOF is positively associated with the risk of mobility disability and poor physical performance over time. Ultimately, the findings in this study improves our understanding of the factors that could lead to functional disability of older adults living in diverse communities and will help design tailored prevention programs.
Methods
This study was part of the International Mobility in Aging Study (IMIAS), a longitudinal multi-site research project examining the various factors related to mobility among community-dwelling older adults at international sites that are different in the culture and the environment. More information on IMIAS methods can be found in a previous publication (11).
As part of IMAIS, in 2012, 1,601 participants (aged 65–74 years) were recruited from Kingston and Saint-Hyacinthe, Canada; Manizales, Colombia; and Natal, Brazil and re-assessed in 2014. At the 2014 assessment, the overall follow-up rate was 85%. FOF was quantified using the Fall Efficacy Scale-International (FES-I) (12). Functional disability measures were (i) self-reported mobility disability, defined as difficulty to climb a flight of stairs or walk 400 m without assistance, and (ii) poor physical performance, defined as a score less than 9 on the Short Physical Performance Battery (SPPB) (13). Since we were studying the incidence of functional disabilities, only participants with no disability at baseline (ie, no reported mobility disability or SPPB score ≥9) were included in the independent analysis of each outcome measure. Ethics approval was obtained from each site and all participants signed an informed consent form.
Statistical Analysis
Distributions of baseline characteristics were described using means (SD), median (interquartile range) for the overall sample and for each site, as suitable. We used Poisson regression models with robust variance to estimate the incidence risk ratios (IRR) and 95% confidence intervals (CI) of functional disability in 2014 among participants without disability in 2012. In order to facilitate results interpretation for clinical practice, FES-I was also tested in separate models as a categorical variable in order to compare those with high FOF against those with low or no FOF. Participants were considered to have no or low FOF if they had a FES-I score of 19 or less, and high FOF if they had a score above 27 (4). Participants with missing values were excluded. A p value of less than .05 was considered statistically significant.
Potential confounding variables were identified using bivariate analyses to test for any association with the outcome variable. Confounders identified from previous literature and with p values less than .1 were included in the multivariate regression models (a separate model was constructed for each outcome). Confounders included in the models were sociodemographic variables (age, sex, site, and education) and clinical variables (visual acuity, depressive symptoms, chronic conditions, cognitive function, grip strength, and physical performance), all measured at baseline. Education was recorded as years of formal education. Habitual binocular visual acuity was tested using the Tumbling E chart placed at two meters; the number of correctly identified “Es” was recorded. Depressive symptoms were assessed using the Center for Epidemiological Studies Depression scale (score: 0–60) (14). Comorbidity was recorded as a total number of chronic conditions (0–8), and global cognition was evaluated using Leganes Cognitive Test score (score: 0–32) (15). Grip strength was measured three times on the dominant side using a Jamar handgrip dynamometer held in sitting position and the maximum value in kilograms was used. The physical performance was evaluated using SPPB (score: 0–12).
Although the tested interaction terms by site were not significant (in the models for the two outcome variables), we decided to stratify the regression analyses by site for descriptive purposes. In order to increase the statistical power after stratification, the four sites were grouped into Canadian (Kingston and Saint-Hyacinthe) or Latin American (Manizales, Colombia; and Natal, Brazil). In the stratified models, we adjusted for the same confounders we used in the original analyses except study site. Statistical analyses were carried out using SAS Enterprise Guide version 6.1 (SAS Institute Inc., Cary, NC).
Results
A total of 1,355 participants completed the 2014 assessment; 917 did not have mobility disability at baseline and entered the analysis for incident mobility disability, and 1,078 had SPBB score ≥9 and entered the analysis for incident poor physical performance. In 2014, 131 (14.3%) and 166 (15.4%) participants reported incident mobility disability and poor physical performance, respectively. Table 1 presents the baseline characteristics of participants who completed 2014. The mean score of FOF at baseline was 24 (SD: 9.0) with 22% of the participants having high FOF (FES-I > 27).
Table 1.
Characteristics of Participants at Baseline Who Completed 2014 Assessment, for the Overall Sample and by Site, Reported as Mean (SD) Unless Otherwise Specified
| Variable | All Participants n = 1,355 | Kingston n = 328 | Saint-Hyacinthe n = 345 | Manizales n = 366 | Natal n = 316 |
|---|---|---|---|---|---|
| Age (years) | 69.0 (2.8) | 69.0 (2.7) | 68.6 (2.7) | 69.3 (3.0) | 69.2 (2.8) |
| Years of education | 9.7 (6.2) | 16.1 (3.9) | 12.2 (4.0) | 5.8 (4.5) | 4.7 (4.0) |
| Fear of falling (FES-I) | 24.0 (9.0) | 20.9 (5.8) | 19.3 (5.0) | 28.9 (10.6) | 25.6 (9.5) |
| Depressive symptoms | 8.5 (8.1) | 6.5 (7.5) | 6.7 (7.0) | 10.2 (8.4) | 10.5 (8.5) |
| Comorbidity (median [IQR]) | 2 (2) | 2 (2) | 2 (1) | 1 (1) | 2 (2) |
| Visual acuity | 45.4 (10.9) | 51.4 (7.7) | 48.2 (8.3) | 38.0 (10.8) | 44.8 (10.5) |
| Global cognition | 28.7 (2.6) | 30.7 (1.2) | 29.2 (1.9) | 27.3 (2.9) | 27.9 (2.6) |
| Grip strength (kg) | 28.7 (10.6) | 31.2 (11.8) | 38.8 (11.2) | 25.6 (7.8) | 25.2 (8.9) |
| Physical Performance (SPPB) | 9.9 (1.9) | 10.4 (1.6) | 10.2 (1.6) | 9.7 (1.8) | 9.2 (2.3) |
Note: FES-I = Falls Efficacy Scale-International (score range: 16 and 64); IQR = Interquartile range; SPPB = Short Physical Performance Battery (score range: 0–12). Depressive symptoms were assessed using the Center for Epidemiological Studies Depression scale (score range: 0–60); comorbidity was recorded as a total number of chronic conditions (0–8); Visual acuity was recorded as the number of correctly identified Es; global cognition was evaluated using Leganes Cognitive Test score (score range: 0–32).
Table 2 shows the results from the multivariate Poisson regression analysis. For the overall sample and after adjusting for age, sex, socioeconomic, and health covariates, a one-point increase in FES-I at baseline was significantly associated with a 4% increase in the risk of reporting incident mobility disability and 3% increase in the risk of developing poor physical performance in 2014. When the FES-I score was categorized, those with a high FOF at baseline had a 175% increase in the risk of reporting incident mobility disability and a 62% increase in the risk of developing poor physical performance in 2014 compared to those with no or low FOF. Even after stratifying by site, FOF at baseline remained significantly associated with the risk of developing mobility disability and poor physical performance in 2014. The relationships seemed to be stronger at the Canadian sites than the Latin American sites.
Table 2.
Poisson Regression Results for the Risk of Developing Incident Mobility Disability and Poor Physical Performance in 2014, Fully Adjusted*
| Overall Sample | Canadian Sites | Latin American Sites | ||||
|---|---|---|---|---|---|---|
| Mobility Disability | Poor Physical Performance | Mobility Disability | Poor Physical Performance | Mobility Disability | Poor Physical Performance | |
| IRR (95% CI) | IRR (95% CI) | IRR (95% CI) | IRR (95% CI) | IRR (95% CI) | IRR (95% CI) | |
| FOF (FES-I: 16–64) | 1.04 (1.02–1.05) | 1.03 (1.01–1.05) | 1.08 (1.04–1.10) | 1.10 (1.05–1.14) | 1.03 (1.01–1.04) | 1.02 (1.01–1.04) |
| High vs. no/low** FOF | 2.75 (1.67–4.52) | 1.62 (1.06–2.47) | 2.54 (1.71–5.52) | 3.22 (1.44–7.10) | 2.23 (1.23–4.01) | 1.61 (1.03–2.55) |
Note: Results are presented for the overall sample and by combined site.
IRR = Incident Risk Ratio; 95% CI = 95% confidence interval.
*Adjusted for sociodemographic variables (age, sex, site, and education) and clinical variables (visual acuity, depressive symptoms, chronic conditions, cognitive state, grip strength, and baseline physical performance). **Fear of falling (FOF) categories used were no or low FOF (16–19 score in FES-I) and high FOF (>27 score in FES-I) and were tested in separate models from the continuous FES-I score.
Discussion
The findings from this longitudinal study support our hypothesis and show that FOF was associated with an incidence of functional disability as measured by self-reported and performance-based outcome measures, after accounting for potential confounders in the overall sample and after stratification by site. Outcomes used in this study (eg, mobility disability) are precursors of more than half of end-stage disabilities in older adults (16). Since FOF is amenable to interventions, further understanding of this longitudinal relationship between FOF and functional disability would provide a basis for screening those at risk and intervening to prevent transition to end-stage disability, a priority for aging research.
Our findings are in line with previous studies that investigated the longitudinal relationship between FOF and functional decline (6–9), although they mainly used self-reported measures of IADL and ADL. One study included a performance-based outcome (ie, habitual gait speed), but it was not significantly associated with FOF (9).
The mechanism by which FOF can lead to physical disability over time is worth further investigation. Available explanations focus mainly on FOF and falls, but these explanations could also be used to understand the relationship with functional disability. Traditionally, researchers have believed that FOF could lead to a vicious cycle beginning with self-imposed reduction in physical activities, thus predisposing individuals to poor balance, slower gait speed, and less muscle strength, which in turn could cause disability over time (1,2). However, some researchers have questioned that the relationship between FOF and functional decline and falls can be fully mediated by self-imposed activity restriction and offered other explanations (6,17). For instance, the FOF direct relationship to disability was explained through a psychological theory in which fall risk is mediated by changes in the allocation of attention and associated alterations in motor control (18). While this theory could be possible to explain the relationship between FOF and falls, its validity needs to be investigated when it comes to functional disability. A further analysis that includes potential mediators is warranted. Future research should investigate whether activity restriction mediates the longitudinal relationship, either fully or partially, and identify when other factors play a role in this relationship.
Clinical and Policy Implications
The findings from this study have clear clinical and policy implications. We found a graded effect of FOF on the risk of developing functional disability over time. Holding all confounders stable, a one-point increase in FES-I score was associated with 4% and 3% increase in the risk of developing disability. This could translate into up to 175% and 62% increase, on average, in the risk of developing mobility disability and poor physical performance over the next 2 years, respectively (for those with high FOF compared to those with low FOF). This large effect for FOF on the risk of developing future disabilities is clinically important and can be used to understand incident functional disability and potentially prevent it or reduce it.
The results of this study provide some support to the importance of implementing tools for the early detection and management of FOF in all geriatric care programs, including geriatric rehabilitation. In addition to predicting disability, FOF was shown in another study to be an independent predictor of short- and mid-term rehabilitation outcomes (9). FOF is modifiable (19); therefore, managing FOF could help improve mobility and functional performance, which in turn could improve social integration in local communities and health-related quality of life (20).
Among the strengths of this study were the diverse population, the longitudinal design, and the use of both self-reported and performance-based outcome measures. The diverse population at multiple, international sites represented in this study helps to generalize the findings to more than one location and confirms that this relationship is present in different cultural contexts. The longitudinal design, in which only those without disability at baseline were followed over time, allows for the prediction of incident cases and confirms which factors are predictors in the relationship under study. A limitation in this study was the relatively short follow-up period (2 years).
In conclusion, we demonstrated that FOF is associated with the onset of functional disability over a 2-year period in a diverse community-based population. The impact of FOF on this population is statistically and clinically important and is associated with a large increase in the risk of developing incident disability. Future studies should investigate potential mediators in the longitudinal relationship, and should provide further evidence for interventions to prevent and treat FOF by targeting it directly and/or targeting relevant modifiable risk factors. Further research should also examine causality of the FOF-disability relationship by testing the impact of reducing FOF on incident disability.
Funding
The IMIAS project was supported by a grant from the Canadian Institutes of Health Research (CIHR), grant number (108751).
Acknowledgments
M.A. was supported by fellowships from the Canadian Institutes of Health Research (CIHR) and Queen’s University at the time of the study.
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