If you don't remember your password, you can reset it by entering your email address and clicking the Reset Password button. You will then receive an email that contains a secure link for resetting your password
If the address matches a valid account an email will be sent to __email__ with instructions for resetting your password
Address correspondence to Kota Tsutsumimoto, PhD, PT, Department of Functioning Activation, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, 7-430 Morioka-machi, Obu City, Aichi Prefecture, 474-8511, Japan.
To elucidate whether a combination of slow gait speed and depressive symptoms result in higher risk of incident disability in older adults than either symptom individually.
Design
Prospective cohort study.
Setting
Obu City, Aichi Prefecture, Japan.
Participants
Participants were 4038 older adults (48.7% male, mean age = 71 years) who met the study inclusion criteria.
Measurements
Longitudinal data on incident disability were collected up to 33 months [median 31 months (interquartile range 29–32 months)] after baseline. We monitored monthly incident disability, defined as Japanese long-term care insurance certification for personal support or care. Baseline measurements included covariates for incident disability, gait speed, and the Geriatric Depression Scale for assessing depressive symptoms. The associations between slow gait, depressive symptoms, or their co-occurrence, and incident disability were examined.
Results
Control participants were the reference in an adjusted Cox proportional hazard regression model. Participants with co-occurring slow gait and depressive symptoms showed a greater risk of incident disability [hazard ratio (HR) 3.08, confidence interval (CI) 95% 2.00–4.75]. Greater risk was also found for participants with slow gait speed alone (HR 2.44, CI 95% 1.71–3.47) and depressive symptoms alone (HR 1.60, CI 95% 1.01–2.53).
Conclusions
Older adults with both risk factors may require early detection and physical and psychological intervention.
With this rapidly growing aging population, treating age-related health problems, such as physical and mental frailty or disability, is becoming crucial. From older adults' health promotion and health economics' perspectives, it is important for older adults without disability to maintain functional independence as long as possible. Thus, identifying incident disability risk factors is essential.
Disability onset in older adults is influenced by physiological, psychological, and social factors.
Age-related declines in gait function may reflect dysfunction of any involved systems, including the musculoskeletal, neurologic, or circulatory systems.
Gait speed at usual pace as a predictor of adverse outcomes in community-dwelling older people an International Academy on Nutrition and Aging (IANA) Task Force.
Thus, assessment of older adults' gait function is useful for detecting incident disability risk. Gait speed is a simple but an important clinical marker of current health and well-being. It is a powerful predictor of health problems including disability in older adults.
Lower extremity function and subsequent disability: Consistency across studies, predictive models, and value of gait speed alone compared with the short physical performance battery.
Aside from mobility declines, mental disorders such as depressive symptoms are incident disability risk factors. Depressed individuals often engage in unhealthy lifestyle behaviors, such as smoking and lack of exercise,
These may exacerbate the symptoms of some medical conditions and ultimately lead to compromised functioning. Furthermore, several prospective studies suggest that late-life depression affects subsequent disability or impedes disability recovery.
Slow gait speed and depressive symptoms are highly prevalent in late life and frequently co-occur. Both phenomena are associated with adverse health outcomes such as disability. In addition, there might be bidirectional longitudinal associations between physical function decline (including slow gait speed) and depressive symptoms.
As such, co-occurring slow gait speed and depressive symptoms for older adults might result in higher incident disability risk than either condition alone; however, it remains unclear whether older adults with these 2 conditions concurrently actually do have a higher risk. Thus, we investigated whether concurrent slow gait speed and depressive symptoms lead to higher incident disability risk in Japanese older adults using longitudinal cohort data.
Methods
Setting and Participants
We used a prospective study design, recruiting participants from the population-based cohort of the Obu Study of Health Promotion for the Elderly (OSHPE), conducted from August 2011 to February 2012 at baseline.
OSHPE inclusion criterion was ≥65 years old at examination. Before recruitment, we excluded 1661 people who participated in another study, were hospitalized or in residential care, or had a certified care level of greater than 3 in the Japanese long-term care insurance (LTCI) system. OSHPE recruitment was conducted by letter invitation to 14,313 individuals, of whom 5104 ultimately participated. After baseline assessment, monthly information on participants' health status, including incident disability as assessed by Japanese LTCI, death, or moving away from Obu city, was monitored. The current study included 4038 participants, excluding 1066 participants based on the following criteria: (1) a history of Parkinson disease (n = 23), Alzheimer disease (n = 9), or stroke (n = 528); (2) severe cognitive impairment [Mini-Mental State Examination (MMSE)
<19; n = 157]; (3) requiring support or care by the LTCI system at baseline (n = 160); or (4) missing values at baseline assessment (n = 189). The Ethics Committee of the National Center for Geriatrics and Gerontology approved the study protocol. The study's purpose, nature, and potential risks were fully explained to the participants. All gave their written informed consent before study participation.
Measure
Disability assessment
During follow-up, we monitored participants' LTCI certification [median 31 months (interquartile range 29–32 months)]. Incident disability was defined as being certified for any level of LTCI service for the first time. The Japanese Government established the nationally uniform criteria for LTCI certification objectively; certification of care need levels for older adults is determined by the results of municipal committee evaluation (ie, Certification Committee for Long-Term Care Need) using these criteria. The process of determining eligibility for LTCI system certification is as follows. An older adult or his caregiver contacts the municipal government to request official certification of the applicant's care needs. Then, a trained local government official visits the older adult's home to evaluate nursing care needs in terms of current physical and mental status. After this official completes the assessment, the results are entered into a computer to (1) calculate the applicant's standardized physical and mental status scores; (2) estimate the care time required for the older adult; and (3) assign a care-need level based on the total estimated care time. The Care Needs Certification Board reviews the data, which include the applicant's primary physician's report. Finally, the applicant was assigned a level of care need (certified support level of 1–2 or care level of 1–5). Every 6 months, the older adult's eligibility was re-evaluated. In the present study, incident disability was defined as being certified for the first time for support level 1–2 or care level 1–5.
Gait speed
Two markers were used to indicate the start and end of a 2.4-m walking path, with a 2-m section to be traversed before passing the start marker so that participants were walking at a comfortable pace by the time they reached the timed path. Participants were asked to continue walking for an additional 2 m past the end of the path to ensure a consistent walking pace while on the timed path. Those with poor mobility were identified according to a cut-off (<1.0 m/s).
The GDS is unique in that it was specifically developed for use with geriatric patients and contains fewer somatic items. The participants were required to respond with a “yes” or a “no” to each question. Those who scored 6 or higher on the GDS had depressive symptoms.
Sex, age, and educational level (years) were collected as sociodemographic variables. Via face-to-face interviews, participants reported any medical diagnoses and medications. Comorbid illnesses considered as confounding variables were hypertension, diabetes mellitus, hyperlipidemia, cardiovascular disease, and osteoarthrosis. Participants were asked about whether they had chronic pain continuing for more than 2 months (yes/no). Global cognitive function was assessed using the MMSE, which is commonly used throughout the world; scores range from 0 to 30.
Physical activity was assessed by the total amount of time spent walking per average day. Finally, participants were asked about usual bedtimes and wake times to calculate self-reported sleep durations.
Statistics
All data entry and analyses were performed using SPSS v 19.0 (SPSS Inc, Chicago, IL). We divided the participants into groups by whether the cut-offs for mobility decline (a gait speed of less than 1.0 m/s) and depressive symptoms (GDS score ≤5). Thus, the groups were as follows: (1) no mobility decline and absence of depressive symptoms (control group); (2) normal gait speed with depressive symptoms (depressive symptoms group); (3) slow gait speed but no depressive symptoms (slow gait speed group); and (4) co-occurring slow gait speed and depressive symptoms (co-occurring group). Continuous data are presented as means ± standard deviations. The study participants' characteristics were compared by gait speed and depression symptom status using Student t-test or the Mann–Whitney U-test for continuous variables and the χ2 test for categorical variables. We calculated the cumulative incident disability during follow-up for each of the 4 groups with Kaplan–Meier curves. Intergroup differences were estimated by the log-rank test. Univariate and multivariate Cox proportional hazard regression models were conducted to calculate the hazard ratios with 95% confidence intervals for incident disability risk. Incident disability was the objective variable and the explanatory variable was the group factor compared with the control group. Model 1 was the crude model. Model 2 added the following covariates: age, sex, and education. Model 3 added hypertension, diabetes mellitus, hyperlipidemia, heart disease, osteoarthrosis, number of medications, pain, MMSE score, physical activity, and sleeping time. Each model calculated hazard ratios and 95% confidence intervals referred to the control group.
Results
Out of the 4038 participants initially recruited, 220 (5.4%) developed incident disability during follow-up, which was a median of 31 months (interquartile range 29–32). The incident disability rates by group can be found in Table 1. Descriptive statistics for the baseline characteristics of the 4 groups are presented in Table 1; all variables, except for sex, significantly differed between groups.
Table 1Baseline Participant Characteristics by Risk Pattern (Control, Depressive Symptoms, Slow Gait Speed, or Co-occurring)
Figure 1 shows the probability of being independent using Kaplan–Meier analysis. The co-occurring group showed a higher rate of incident disability than the slow gait speed and depressive symptoms groups. The log-rank test revealed significant differences in incident disability rates between the groups (Table 2).
Fig. 1Kaplan–Meier survival curves of older adults showing the relationship between incident disability and functional decline (slow gait speed, depressive symptoms, or their co-occurrence).
Finally, Table 3 shows the unadjusted and adjusted probabilities of survival for groups using Cox proportional hazard risk analysis. In the crude and 2 adjusted models, the co-occurring group showed significantly highest risk of incident disability, followed by the slow gait speed and depressive symptoms groups, respectively (Table 3).
Table 3Association of Co-occurring Slow Gait Speed and Depressive Symptom With Incident Disability
Risk Pattern
At Risk
Events
Rate per 1000 Person-Years
Crude Model
Adjusted Model 1
Adjusted Model 2
N
N
HR (95% CI) and P Value
Co-occurring
157
38
88.0
9.92 (6.77–14.54)
<.001
4.40 (2.91–6.63)
<.001
3.08 (2.00–4.75)
<.001
Slow gait speed
449
72
58.3
6.08 (4.45–8.32)
<.001
3.00 (2.12–4.23)
<.001
2.44 (1.71–3.47)
<.001
Depressive symptom
399
24
21.9
2.17 (1.38–3.41)
<.001
1.85 (1.18–2.92)
.008
1.60 (1.01–2.53)
.046
Control
3033
86
10.3
Reference
Reference
Reference
CI, confidence interval; HR, hazard ratio.
Significance set at P < .05.
Adjusted model 1: adjusted for age, sex, and education.
Adjusted model 2: adjusted for model 1 covariates, hypertension, diabetes mellitus, hyperlipidemia, heart disease, osteoarthrosis, number of medications, pain, MMSE score, physical activity, and sleeping time.
This study showed that the incident disability rate was 5.4% for a median follow-up of 31 months in community-dwelling older adults. In addition, slow gait speed and depressive symptoms were independent risk factors of incident disability and co-occurring slow gait speed and depressive symptoms presented the highest risk of incident disability. This association remained after adjusting for covariates.
This is the first study that examined the combined effects of depressive symptoms and slow gait speed on incident disability compared with the individual effects of these factors. Accumulating evidence suggests that depressive symptoms are a risk factor for physical dysfunction
The course of functional decline in older people with persistently elevated depressive symptoms: Longitudinal findings from the Cardiovascular Health Study.
One possible explanation of our results is that slow gait speed and depressive symptom form a vicious cycle whereby slow gait induces depressive symptoms; namely, difficulty walking results in decreased physical activities and a restricted living space, which subsequently result in a loss of social support and isolation and eventually leads to depressive symptoms and depression.
In contrast, depressive symptoms can then lead to physical dysfunction by feelings of discouragement and hopelessness, which reduce people's willingness to attempt tasks that they are otherwise capable of performing.
Subsequently, this decrease in physical activities and life space restriction might lead to physical function decline, eventually leading to slow gait speed. The association between slow gait speed and depressive symptoms appears to be bidirectional in older adults.
Based on these previous and our current findings, slow gait speed and depressive symptoms in older adults appear to have an interactive effect on incident disability.
Slow gait speed had greater impact on incident disability than depressive symptoms. Previous studies indicated that slow gait speed has a higher risk of incident disability.
Lower extremity function and subsequent disability: Consistency across studies, predictive models, and value of gait speed alone compared with the short physical performance battery.
In the present study, incident disability was defined as being certified for personal support and care by the LTCI system, and nearly half (47.5%) of the incident disability cases were certified support levels 1 or 2. The older adults with support levels 1 or 2 require relatively little personal care compared with those certified for care levels 1–5; however, the support levels are a transition phase to the care levels. In support levels 1 and 2, certification causes were as follows: aging-related debilitation, 20.7%; arthritic disorders, 15.4%; and fall and bone fractures, 14.6%.
These causes were thought to have a direct link with mobility. Thus, the LTCI system's method of classifying disability might have partially contributed to the result that slow gait speed had a high risk of incident disability.
The central strengths of the present study are as follows. First, we used a robust and objective assessment of incident disability created by the Japanese Government. In most studies of incident disability in older adults, disability is assessed by subjective methods such as questionnaires. Second, disability assessment is frequent; it is conducted monthly by the Japanese Government. Thus, changes in participants' functional status are identified quickly and in detail, although the observation period in the present study was relatively short compared with other studies of incident disability.
A major strength of this longitudinal study is the application of monthly disability follow-up in a large sample using the mandatory social LTCI in Japan. Nevertheless, several limitations should be considered. First, the 33-month follow-up might have been too short to sufficiently capture incident disability and our follow-up period was shorter than previous studies.
Furthermore, incident disability end points were too small to investigate prospective associations of slow gait speed and depressive symptoms with incident disability. Second, some variables were self-reported (eg, education history, comorbidity, physical activity). These factors and others should be examined in future studies. Future studies examining causes of incident disability and longitudinal relationships between slow gait speed, depressive symptoms, and disability using longer follow-up data would be helpful to consider preventive strategies for disability.
Acknowledgments
We thank the staff of the Obu City office for their help with participant recruitment.
References
Aare M.
von Holst H.
Injuries from motorcycle- and moped crashes in Sweden from 1987 to 1999.
Gait speed at usual pace as a predictor of adverse outcomes in community-dwelling older people an International Academy on Nutrition and Aging (IANA) Task Force.
Lower extremity function and subsequent disability: Consistency across studies, predictive models, and value of gait speed alone compared with the short physical performance battery.
The course of functional decline in older people with persistently elevated depressive symptoms: Longitudinal findings from the Cardiovascular Health Study.
This work was supported by the Japanese Ministry of Health, Labor, and Welfare (Project for Optimizing Long-Term Care; grant number B-3) and the National Center for Geriatrics and Gerontology (Research Funding for Longevity Sciences; grant number 22-16).
00551-4&id=gr1.jpg){kind=link}