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Daily Physical Activity Predicts Frailty Development Among Community-Dwelling Older Japanese Adults
JAMDA xxx (2019) 1e5
JAMDA journal homepage: www.jamda.com
Original Study
Daily Physical Activity Predicts Frailty Development Among Community-Dwelling Older Japanese Adults Atsumu Yuki PhD a, *, Rei Otsuka PhD b, Chikako Tange PhD b, Yukiko Nishita PhD b, Makiko Tomida PhD b, Fujiko Ando MD, PhD c, Hiroshi Shimokata MD, PhD d, Hidenori Arai MD, PhD e a
Faculty of Education, Kochi University, Kochi, Japan Section of the NILS-LSA, National Center for Geriatrics and Gerontology, Aichi, Japan Faculty of Health and Medical Sciences, Aichi Shukutoku University, Aichi, Japan d Graduate School of Nutritional Sciences, Nagoya University of Arts and Sciences, Aichi, Japan e Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Aichi, Japan b c
a b s t r a c t Keywords: Number of steps moderate- to vigorous-intensity physical activity accelerometer NILS-LSA
Objectives: This study examined the association between frailty development and physical activity including the number of steps, the time of light-intensity physical activity (LPA) with <3.0 metabolic equivalents (METs), and the time of moderate- to vigorous-intensity physical activity (MVPA) with 3.0 METs in community-dwelling older Japanese adults. Design, setting, and participants: Study subjects were 401 older adults at the baseline examination (April 2000eMay 2002) who participated at least once in the follow-up examination of the longitudinal study of aging. Their 1787 cumulative data points (mean number of repeat visits, 3.5) were used for analysis. Measures: The number of steps, time of LPA, and time of MVPA were recorded at baseline using a uniaxial accelerometer. Frailty was defined according to 5 frailty criteria: shrinking, exhaustion, low physical activity, low grip strength, and slow gait speed. Results: The fully adjusted odds ratio for frailty among subjects walking <5000 steps was 1.85 [95% confidence interval (CI), 1.10-3.11]. The fully adjusted odds ratio for frailty among subjects with MVPA for <7.5 minutes was 1.80 (95% CI, 1.05-3.09). No significant association was observed between frailty and LPA. Conclusions and Implications: The risk for developing frailty was substantially lower in older people walking 5000 steps/d or exercising for at least 7.5 minutes/d at an intensity >3.0 METs. These data could be applicable to the community interventions that aim to prevent frailty. Ó 2019 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
Prevention of frailty is a global concern, because the population is rapidly aging. There are currently more than 600 million older people worldwide, and it is predicted that this number will increase to 1800 million people by 2060.1 The development of programs to prevent frailty is a pressing task. In the Cardiovascular Health Study, a decrease of residual physiological function with aging included 5 symptoms of physical frailty: shrinking, exhaustion, weakness, low activity, and slowness.2 Exercise This work was supported by the JSPS KAKENHI (16H03264) and Research Funding for Longevity Sciences (28-40) from the National Center for Geriatrics and Gerontology in Japan. The authors declare no conflicts of interest. * Address correspondence to Atsumu Yuki, PhD, Kochi University, 2-5-1 Akebono, Kochi City, Kochi 780-8520, Japan. E-mail address: [email protected] (A. Yuki). https://doi.org/10.1016/j.jamda.2019.01.001 1525-8610/Ó 2019 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
and physical activity improve these symptoms and reduce the prevalence of frailty.3 It is well known that exercise increases skeletal muscle mass and improves muscle strength in older adults.4,5 Furthermore, acceleration of blood circulation and the endocrine response to exercise improve the serotonergic system and promote brain function and neuropoiesis via brain-derived neurotrophic factor.6e8 In addition, an intervention consisting of exercise and physical activity also improves frailty symptoms and reduces the prevalence of frailty.9e12 Therefore, habits that include increased physical activity and exercise may contribute to the prevention of frailty in older adults. It is unknown whether daily physical activity contributes to the prospective prevention of frailty. No objective cutoff values for factors associated with the development of the frailty have been established, although daily physical activity has been shown to contribute to the
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A. Yuki et al. / JAMDA xxx (2019) 1e5
maintenance of physical function and mental health.13 Indeed, several cross-sectional studies reported that sedentary time was a biomarker of frailty.14e16 The prevalence of physical prefrailty, which is associated with a higher risk for the development of frailty,17 is approximately 50% among older people aged 65 years18,19; thus, half of older people may develop frailty. This study investigated the association between the development of frailty and daily physical activity using 10-year follow-up examinations. The physical activities studied were assessed by an accelerometer, which allowed the development of objective values for each variable. Methods Subjects This study included older subjects who participated in the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILSLSA). The NILS-LSA is a population-based biennial survey of a dynamic cohort of approximately 2300 persons.20 Participants in the NILS-LSA were randomly selected from registered residents and stratified according to both sex and decade of age. The Ethics Committee approved the study protocol. All participants provided written informed consent for participation in the present study. This study used data from the second-wave examination to the seventh-wave examination of the NILS-LSA. Baseline participants in this study included 853 subjects aged 65-82 years who participated in the second-wave examination of the NILS-LSA between April 2000 and May 2002. Of these subjects, 753 completed the assessments of physical activity continuously for a 7-day period at the second-wave examination of the NILS-LSA. Of these subjects, 158 did not complete the assessments of frailty at baseline. Frail participants in the baseline examination (n ¼ 28) were excluded to examine the longitudinal association between the development of frailty and physical activity. The 66 subjects who had missing data with covariates were also excluded. The 100 subjects who never participated in follow-up examinations were also excluded. Finally, 401 subjects were included in this study. Among them, 393 (98.0%) took part in the third wave of the NILS-LSA between May 2002 and May 2004, 323 (80.5%) took part in the fourth-wave examination between June 2004 and July 2006, 271 (67.6%) took part in the fifth-wave examination between July 2006 and July 2008, 221 (55.1%) took part in the sixth-wave examination between July 2008 and July 2010, and 178 (44.4%) took part in the seventh wave between July 2010 and July 2012. The mean number of repeat visits was 3.5. The total number of visits, including repeat visits, was 1787. Physical Activity Assessment Daily physical activities of study subjects at baseline were recorded using a uniaxial accelerometry sensor (Lifecorder; Suzuken, Aichi, Japan). Subjects wore the accelerometry sensor continuously (except while sleeping or bathing) for a 7-day period. Any special event, such as a trip, was not included in the 7-day measuring period. The accelerometry sensor measures the number of steps taken and the intensity of physical activity every 4 seconds throughout the day. It was confirmed that subjects wore an accelerometry sensor every day for 10 hours.21,22 Activity data, which were recorded continuously for 7 days, were used for assessment of physical activity. The number of steps was used as 1 indicator of physical activity. Additionally, activity time recorded by an accelerometer was categorized into 10 activity levels rated on a scale from 0 to 9. These activity levels were converted into metabolic equivalents (METs)23 and were divided into 3 categories: slight physical activity (<1.8 METs),
light-intensity physical activity (LPA; 1.8 to <3.0 METs), and moderate- to vigorous-intensity physical activity (MVPA; 3.0 METs). In our analysis, time of LPA and time of MVPA were used as indicators of physical activity. Frailty Assessment Frailty assessment was performed based on a modification of the Cardiovascular Health Study criteria for Japanese older adults,2,19 because standardized criteria for frailty for older Japanese subjects were not established until 2018. Frailty was assessed using the following 5 criteria: shrinking, exhaustion, weakness, low activity, and slowness. Frailty was defined as meeting 3 of these criteria, prefrailty was defined as meeting 1 or 2 criteria, and robust was defined as having none of these criteria. These modified criteria were shown to be associated with the incidence of early death and a decline of higher-level functional capacity in older Japanese adults.24,25 The criteria for frailty have been previously described.19,24 Shrinking was assessed by unintentional weight loss of 5% in the prior 2 years.19 Exhaustion was assessed by questions 7 and 20 from the Center for Epidemiologic StudieseDepression scale. If participants did not answer “rarely or none of the time” to these questions, they were defined as having exhaustion.19 Weakness was assessed by grip strength, and the cutoff point for weakness was 26 kg in men and 18 kg in women.19 Low physical activity was defined as the lowest 20% of leisure-time physical activity by sex.19 Slowness was assessed by comfortable gait speed, and the cutoff point for slowness was 1.0 m/s for men and women.19 Other Parameters Percentage of body fat was assessed by dual-energy x-ray absorptiometry (QDR-4500; Hologic, Marlborough, MA). Data regarding current smoking habits and medical history were assessed using selfcompleted questionnaires and were confirmed by a physician following a medical examination. The number of comorbidities was defined as the sum of a history of cerebrovascular disease, heart disease, cancer, diabetes, hypertension, dyslipidemia, osteoporosis, arthritis, anemia, dementia, and depression symptoms. The mean total caloric intake per day (kcal/d) was calculated from a 3-day dietary record.26 Education history was assessed using self-completed questionnaires. Statistical Analysis SAS 9.3 (SAS Institute Inc, Cary, NC) was used for all statistical analyses. P values <.05 were considered statistically significant. Data are presented as mean standard deviation. Cumulative data were analyzed using the generalized estimate equation (GEE). The number of steps and physical activity levels were modeled as dichotomized variables in GEE analyses. In this study, the cut-off value of the number of steps, LPA, and MVPA was 5000 steps/d, 40.3 minutes/d, and 7.5 minutes/d, respectively. The cut-off values of the number of steps and MVPA were associated with health-related quality of life among community-dwelling Japanese older adults.13 However, the cut-off value of LPA was not reported in that previous study. The daily 5000 steps and MVPA of 7.5 minutes were approximately equal to the 25th percentile of study subjects in this study. Thus, the cut-off value of LPA was defined as the 25th percentile of LPA (40.3 minutes/d). GEE models were used to determine the associations of physical activities with frailty using adjusted models with confounders. Model 1 was adjusted for follow-up year (continuous variable) and sex and age at baseline (years; continuous variable). Model 2 was further adjusted for follow-up year (continuous variable), sex, age, body fat (continuous variable), education (continuous variable),
A. Yuki et al. / JAMDA xxx (2019) 1e5 Table 1 Characteristics of Participants at Baseline Subjects (N ¼ 401)
Mean (SD) or n (%)
Women Age, y Frailty status Robust Prefrailty Number of steps/d Light-intensity physical activity, min/d Moderate- to vigorous-intensity physical activity, min/d Body fat, % Education, y Energy intake, kcal/d Current smoker Comorbidities Cerebrovascular disease Heart disease Cancer Diabetes Hypertension Dyslipidemia Osteoporosis Arthritis Anemia Dementia Depression
178 (44.4%) 71.1 (4.3) 170 231 7204.1 55.5 20.4
(42.4%) (57.6%) (3500.3) (22.8) (19.2)
26.6 10.6 2022.4 57 1.4 22 40 22 38 160 90 38 60 41 11 31
(6.8) (2.7) (395.8) (14.2%) (1.2) (5.5%) (10.0%) (5.5%) (9.5%) (39.9%) (22.4%) (9.5%) (15.0%) (10.2%) (2.7%) (7.7%)
SD, standard deviation.
current smoking (no, yes), energy intake (continuous variable), number of comorbidities (continuous variable), and frailty status (robust or prefrailty) at baseline. Model 2 was also used to determine the associations of physical activities with each frailty criterion. Results The mean (standard deviation) follow-up period was 4.2 (3.4) years. Table 1 presents the baseline characteristics of the 401 participants. The mean (range) number of steps, time of LPA, and time of MVPA of subjects were 7204.1 steps/d (627.6-22,870.4 steps/d), 55.5 minutes/d (6.4-154.6 minutes/d), and 20.4 minutes/ d (0.1-103.6 minutes/d), respectively. Table 2 shows the results of GEE to determine the associations of physical activities with frailty. Significant associations between subjects walking <5000 steps and frailty were noted in model 1 (P < .01) and model 2 (P < .05). Significant associations between frailty and Table 2 Longitudinal Relationship Between Physical Activity and Frailty Activity
Number of steps <5000 steps/d 5000 steps/d LPA (1.8-3.0 METs) <40.3 min/d 40.3 min/d MVPA (3.0 METs) <7.5 min/d 7.5 min/d
Cases
Model 1
Model 2
OR (95% CI)
OR (95% CI)
46/477 62/1310
2.09 (1.25-3.49)* 1.00 (Reference)
1.85 (1.10-3.11)y 1.00 (Reference)
37/433 71/1354
1.55 (0.93-2.60) 1.00 (Reference)
1.35 (0.82-2.25) 1.00 (Reference)
45/462 63/1325
2.07 (1.24-3.48)* 1.00 (Reference)
1.80 (1.05-3.09)y 1.00 (Reference)
Model 1 was adjusted for follow-up year (continuous variable) and sex and age at baseline (years; continuous variable). Model 2 was adjusted for follow-up year (continuous variable), sex, age, body fat (continuous variable), education (continuous variable), current smoking (no, yes), energy intake (continuous variable), number of comorbidities (continuous variable), and frailty status (robust or prefrailty) at baseline. Chi-square test. *P < .05. y P < .01.
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subjects with <7.5 minutes/d of MVPA were noted in model 1 (P < .01) and model 2 (P < .05). Modeling the number of steps as a continuous variable in model 2, the odds ratio (OR) (95% confidence interval [CI]) for development of frailty with an increase in 1000 steps was 0.92 (0.84-1.01; P ¼ .09). Modeling the time of LPA and MVPA as a continuous variable in model 2, the OR (95% CI) for a development of frailty with an increase in 10 minutes was 0.96 (0.82-1.11; P ¼ .57) and 0.83 (0.70-0.97; P < .05), respectively. The fully adjusted OR (95% CI) for the development of low activity in subjects walking <5000 steps daily and with <7.5 minutes of MVPA daily was 1.72 (1.12-2.64; P < .05) and 1.92 (1.26-2.92; P < .01), respectively. In addition, the fully adjusted OR (95% CI) for the development of slowness in subjects walking <5000 steps daily and with <7.5 minutes of MVPA daily was 2.01 (1.17-3.44; P < .05) and 3.19 (1.90-5.34; P < .0001), respectively. No other significant associations were noted between the frailty criteria and physical activity (data not shown). Discussion The present study demonstrated that daily steps and time of MVPA can predict physical frailty in older Japanese adults during a 10-year follow-up period. Both of these variables were objective values based on data records of accelerometers. These results are consistent with previous cross-sectional and randomized control trials that showed an association between sedentary lifestyle and frailty.3,14e16,27 In the present study, <5000 steps/d or MVPA of <7.5 minutes/d, which were the cutoff values for an impact on health-related quality of life, were associated with the development of frailty. In a study using the data of yearlong measurements of physical activity for older Japanese people, a higher level of physical activity was shown to be associated with a higher level of metabolic and physical health and lower health care costs in older Japanese adults.13,28 In particular, the cut-offs for physical health were 7000 steps/d or an MVPA of 15 minutes/d.29 A randomized control trial that used physical activity among older American adults to assess those with a high risk for mobility disability reported that the prevalence of frailty was decreased by walking (the intensity of training was gradually increased during the intervention period) at least 20 minutes/d.3 Another study that used the combination of walking (up to 20 minutes/d), strength, balance, and flexibility exercises also reported that the incidence of frailty among nonfrail participants for the first 6 months was lower in the group that participated in physical activity than in the group that underwent health education.27 The levels of physical activity associated with the development of frailty in the current study were lower than in these previous studies. The discrepancy between previous studies and this study might be caused by the difference in populations, particularly the mean age of the subjects, or in study designs, such as the difference between an observational study and an intervention study. Moreover, in this study, subjects who met the frailty definition at baseline were excluded. For older, nonfrail people, excessive physical activity might not be needed to prevent frailty. The lower mark for physical activity used in this study may contribute to interventions that encourage participation in physical activity to prevent frailty in old people. A time of MVPA of <7.5 minutes/d was significantly associated with the development of frailty. A previous study using an accelerometer for older Japanese adults showed that the reference value of 3 METs of physical activity for the maintenance of mental and physical health was 15 minutes/d.13 Our findings of an MVPA of 7.5 minutes/d (3.0 METs) to predict the development of frailty were consistent with those results. Interestingly, it is possible that physical activities with a higher intensity than walking, such as doing laundry, playing with animals, bicycling, and jogging,30,31 might contribute to the prevention of frailty even if the time engaged in MVPA is short.
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A. Yuki et al. / JAMDA xxx (2019) 1e5
Although <5000 steps daily, which equals about 50 minutes of activity, was associated with the development of frailty, the results in this study also suggest that walking for more than 1 hour is not always associated with the prevention of frailty. Various daily activities with a higher intensity than walking may be suitable for the prevention of frailty and may allow for the development of different programs to help prevent frailty in older people. A significant association was observed between daily steps, MVPA, low physical activity, and development of slowness. The low activity and steps and MVPA might be closely related. In a longitudinal study with a 4-year follow-up, physical activity predicted the decline of gait speed.32 Similarly, slow gait speed was longitudinally associated with the development of disability in activities of daily living33,34 and the incidence of certified need for care in the longterm care insurance system in Japan.35 In this study, walking 5000 steps/d or an MVPA of 7.5 minutes/d appeared to contribute to the prevention of frailty. No significant association was observed between LPA and frailty development. The precise reasons for this observation are unknown, but activities with 1.8 to 2.9 METs include housework, a light-conditioning exercise, or light work in the standing position.30,31 Activities with 1.8 to 2.9 METs appear to lack locomotion, brisk movement, or an increase of heart rate. Therefore, absolute deficiency of stimulus by LPA might not prevent the development of frailty. The criteria of physical activity for health promotion in Japan recommend an increase in physical activity of 1500 steps/d or 10 minutes/d.36,37 In this study, a dose-response relationship between MVPA time and frailty development was observed. Increasing physical activity with as much locomotion as possible may contribute to the prevention of frailty. Further studies that focus on the cumulative effect of daily physical activity are necessary to determine additional activity factors that may promote better health in older adults. This study has several limitations. First, physical activity was recorded by a uniaxial accelerometer, not a triaxial accelerometer as was used in other recent studies. Second, lifestyle modifications of study subjects were not known. For example, medical episodes during the follow-up period might have decreased physical activity. An interest in well-being might have also led to a voluntary increase in physical activity. Third, the measuring period with the accelerometer was only 7 days. Finally, the generalizability of these findings to older adults in other countries cannot be confirmed. In particular, people in East Asian countries, including Japan, appear to walk more than people in other countries such as the United States or European countries.38 A study that measured MVPA time for Americans using an accelerometer reported that the mean MVPA time in men and women aged 60-69 years was 16.7 minutes/d and 12.4 minutes/d, respectively.22 The mean MVPA time in this study was 20.4 (19.2) minutes/d. It is not clear if 5000 steps/d or MVPA time of 7.5 minutes/d is enough stimulation to prevent frailty in older people with lower levels of physical activity than the population in this study. Conclusions and Implications In conclusion, this study examined the association between physical activity including the number of steps, LPA equivalent to <3.0 METs, and MVPA 3.0 METs as predictors of frailty development using 1787 cumulative data points from 401 community-dwelling older Japanese adults. The risk for developing frailty was substantially lower in older people walking 5000 steps/d or exercising 7.5 minutes/d at an intensity of 3.0 METs. Objective values associated with frailty development might contribute to the development of physical activity reference values for frailty prevention.
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Association between sedentary time and mortality across levels of frailty. CMAJ 2017;189:E1056eE1064. 16. Virtuoso Júnior JS, Roza LB, Tribess S, et al. Time spent sitting is associated with changes in biomarkers of frailty in hospitalized older adults: A cross sectional study. Front Physiol 2017;8:505. 17. Espinoza SE, Jung I, Hazuda H. Lower frailty incidence in older Mexican Americans than in older European Americans: The San Antonio Longitudinal Study of Aging. J Am Geriatr Soc 2010;58:2142e2148. 18. Kojima G, Iliffe S, Taniguchi Y, et al. Prevalence of frailty in Japan: A systematic review and meta-analysis. J Epidemiol 2017;27:347e353. 19. Yuki A, Otsuka R, Tange C, et al. Epidemiology of frailty in elderly Japanese. J Phys Fit Sport Med 2016;5:301e307. 20. Shimokata H, Ando F, Niino N. A new comprehensive study on agingdThe National Institute for Longevity Sciences, Longitudinal Study of Aging (NILS-LSA). J Epidemiol 2000;10(1 suppl):S1eS9. 21. Mâsse LC, Fuemmeler BF, Anderson CB, et al. Accelerometer data reduction: A comparison of four reduction algorithms on select outcome variables. Med Sci Sports Exerc 2005;37(11 suppl). 22. Troiano RP, Berrigan D, Dodd KW, et al. Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc 2008;40:181e188. 23. Kumahara H, Schutz Y, Ayabe M, et al. The use of uniaxial accelerometry for the assessment of physical-activity-related energy expenditure: A validation study against whole-body indirect calorimetry. Br J Nutr 2004; 91:235. 24. Yuki A, Otsuka R, Tange C, et al. Physical frailty and mortality risk in Japanese older adults. Geriatr Gerontol Int 2018;18:1085e1092. 25. Yuki A, Otsuka R, Tange C, et al. The relationship between the frailty and the high-level functional capacity. J Phys Fit Sport Med 2017;6:490. 26. Imai T, Otsuka R, Katou Y, et al. Advantages of taking photographs with the 3-day dietary record. J Integr Study Diet Habits 2009;20:203e210. 27. Trombetti A, Hars M, Hsu F, et al. Effect of physical activity on frailty. Ann Intern Med 2018;168:309. 28. Aoyagi Y, Shephard RJ. A model to estimate the potential for a physical activity-induced reduction in healthcare costs for the elderly, based on pedometer/accelerometer data from the Nakanojo study. Sport Med 2011;41: 695e708. 29. Aoyagi Y, Park H, Watanabe E, et al. Habitual physical activity and physical fitness in older Japanese adults: The Nakanojo Study. Gerontology 2009;55: 523e531.
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34. Shimada H, Makizako H, Doi T, et al. Incidence of disability in frail older persons with or without slow walking speed. J Am Med Dir Assoc 2015;16:690e696. 35. Akune T, Muraki S, Oka H, et al. Incidence of certified need of care in the long-term care insurance system and its risk factors in the elderly of Japanese population-based cohorts: The ROAD study. Geriatr Gerontol Int 2014;14: 695e701. 36. Health Sciences Council of Japan. Reference material on promotion of Health Japan 21 (the second term); 2012. 37. Ministry of Health Labour and Welfare of Japan. Active Guide - Japanese official physical activity guidelines for health promotion. Available at: http://www. nibiohn.go.jp/eiken/info/pdf/active2013-e.pdf; 2013. Accessed February 1, 2019. 38. Althoff T, Sosi c R, Hicks JL, et al. Large-scale physical activity data reveal worldwide activity inequality. Nature 2017;547:336e339.
JAMDA journal homepage: www.jamda.com
Original Study
Daily Physical Activity Predicts Frailty Development Among Community-Dwelling Older Japanese Adults Atsumu Yuki PhD a, *, Rei Otsuka PhD b, Chikako Tange PhD b, Yukiko Nishita PhD b, Makiko Tomida PhD b, Fujiko Ando MD, PhD c, Hiroshi Shimokata MD, PhD d, Hidenori Arai MD, PhD e a
Faculty of Education, Kochi University, Kochi, Japan Section of the NILS-LSA, National Center for Geriatrics and Gerontology, Aichi, Japan Faculty of Health and Medical Sciences, Aichi Shukutoku University, Aichi, Japan d Graduate School of Nutritional Sciences, Nagoya University of Arts and Sciences, Aichi, Japan e Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Aichi, Japan b c
a b s t r a c t Keywords: Number of steps moderate- to vigorous-intensity physical activity accelerometer NILS-LSA
Objectives: This study examined the association between frailty development and physical activity including the number of steps, the time of light-intensity physical activity (LPA) with <3.0 metabolic equivalents (METs), and the time of moderate- to vigorous-intensity physical activity (MVPA) with 3.0 METs in community-dwelling older Japanese adults. Design, setting, and participants: Study subjects were 401 older adults at the baseline examination (April 2000eMay 2002) who participated at least once in the follow-up examination of the longitudinal study of aging. Their 1787 cumulative data points (mean number of repeat visits, 3.5) were used for analysis. Measures: The number of steps, time of LPA, and time of MVPA were recorded at baseline using a uniaxial accelerometer. Frailty was defined according to 5 frailty criteria: shrinking, exhaustion, low physical activity, low grip strength, and slow gait speed. Results: The fully adjusted odds ratio for frailty among subjects walking <5000 steps was 1.85 [95% confidence interval (CI), 1.10-3.11]. The fully adjusted odds ratio for frailty among subjects with MVPA for <7.5 minutes was 1.80 (95% CI, 1.05-3.09). No significant association was observed between frailty and LPA. Conclusions and Implications: The risk for developing frailty was substantially lower in older people walking 5000 steps/d or exercising for at least 7.5 minutes/d at an intensity >3.0 METs. These data could be applicable to the community interventions that aim to prevent frailty. Ó 2019 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
Prevention of frailty is a global concern, because the population is rapidly aging. There are currently more than 600 million older people worldwide, and it is predicted that this number will increase to 1800 million people by 2060.1 The development of programs to prevent frailty is a pressing task. In the Cardiovascular Health Study, a decrease of residual physiological function with aging included 5 symptoms of physical frailty: shrinking, exhaustion, weakness, low activity, and slowness.2 Exercise This work was supported by the JSPS KAKENHI (16H03264) and Research Funding for Longevity Sciences (28-40) from the National Center for Geriatrics and Gerontology in Japan. The authors declare no conflicts of interest. * Address correspondence to Atsumu Yuki, PhD, Kochi University, 2-5-1 Akebono, Kochi City, Kochi 780-8520, Japan. E-mail address: [email protected] (A. Yuki). https://doi.org/10.1016/j.jamda.2019.01.001 1525-8610/Ó 2019 AMDA e The Society for Post-Acute and Long-Term Care Medicine.
and physical activity improve these symptoms and reduce the prevalence of frailty.3 It is well known that exercise increases skeletal muscle mass and improves muscle strength in older adults.4,5 Furthermore, acceleration of blood circulation and the endocrine response to exercise improve the serotonergic system and promote brain function and neuropoiesis via brain-derived neurotrophic factor.6e8 In addition, an intervention consisting of exercise and physical activity also improves frailty symptoms and reduces the prevalence of frailty.9e12 Therefore, habits that include increased physical activity and exercise may contribute to the prevention of frailty in older adults. It is unknown whether daily physical activity contributes to the prospective prevention of frailty. No objective cutoff values for factors associated with the development of the frailty have been established, although daily physical activity has been shown to contribute to the
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maintenance of physical function and mental health.13 Indeed, several cross-sectional studies reported that sedentary time was a biomarker of frailty.14e16 The prevalence of physical prefrailty, which is associated with a higher risk for the development of frailty,17 is approximately 50% among older people aged 65 years18,19; thus, half of older people may develop frailty. This study investigated the association between the development of frailty and daily physical activity using 10-year follow-up examinations. The physical activities studied were assessed by an accelerometer, which allowed the development of objective values for each variable. Methods Subjects This study included older subjects who participated in the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILSLSA). The NILS-LSA is a population-based biennial survey of a dynamic cohort of approximately 2300 persons.20 Participants in the NILS-LSA were randomly selected from registered residents and stratified according to both sex and decade of age. The Ethics Committee approved the study protocol. All participants provided written informed consent for participation in the present study. This study used data from the second-wave examination to the seventh-wave examination of the NILS-LSA. Baseline participants in this study included 853 subjects aged 65-82 years who participated in the second-wave examination of the NILS-LSA between April 2000 and May 2002. Of these subjects, 753 completed the assessments of physical activity continuously for a 7-day period at the second-wave examination of the NILS-LSA. Of these subjects, 158 did not complete the assessments of frailty at baseline. Frail participants in the baseline examination (n ¼ 28) were excluded to examine the longitudinal association between the development of frailty and physical activity. The 66 subjects who had missing data with covariates were also excluded. The 100 subjects who never participated in follow-up examinations were also excluded. Finally, 401 subjects were included in this study. Among them, 393 (98.0%) took part in the third wave of the NILS-LSA between May 2002 and May 2004, 323 (80.5%) took part in the fourth-wave examination between June 2004 and July 2006, 271 (67.6%) took part in the fifth-wave examination between July 2006 and July 2008, 221 (55.1%) took part in the sixth-wave examination between July 2008 and July 2010, and 178 (44.4%) took part in the seventh wave between July 2010 and July 2012. The mean number of repeat visits was 3.5. The total number of visits, including repeat visits, was 1787. Physical Activity Assessment Daily physical activities of study subjects at baseline were recorded using a uniaxial accelerometry sensor (Lifecorder; Suzuken, Aichi, Japan). Subjects wore the accelerometry sensor continuously (except while sleeping or bathing) for a 7-day period. Any special event, such as a trip, was not included in the 7-day measuring period. The accelerometry sensor measures the number of steps taken and the intensity of physical activity every 4 seconds throughout the day. It was confirmed that subjects wore an accelerometry sensor every day for 10 hours.21,22 Activity data, which were recorded continuously for 7 days, were used for assessment of physical activity. The number of steps was used as 1 indicator of physical activity. Additionally, activity time recorded by an accelerometer was categorized into 10 activity levels rated on a scale from 0 to 9. These activity levels were converted into metabolic equivalents (METs)23 and were divided into 3 categories: slight physical activity (<1.8 METs),
light-intensity physical activity (LPA; 1.8 to <3.0 METs), and moderate- to vigorous-intensity physical activity (MVPA; 3.0 METs). In our analysis, time of LPA and time of MVPA were used as indicators of physical activity. Frailty Assessment Frailty assessment was performed based on a modification of the Cardiovascular Health Study criteria for Japanese older adults,2,19 because standardized criteria for frailty for older Japanese subjects were not established until 2018. Frailty was assessed using the following 5 criteria: shrinking, exhaustion, weakness, low activity, and slowness. Frailty was defined as meeting 3 of these criteria, prefrailty was defined as meeting 1 or 2 criteria, and robust was defined as having none of these criteria. These modified criteria were shown to be associated with the incidence of early death and a decline of higher-level functional capacity in older Japanese adults.24,25 The criteria for frailty have been previously described.19,24 Shrinking was assessed by unintentional weight loss of 5% in the prior 2 years.19 Exhaustion was assessed by questions 7 and 20 from the Center for Epidemiologic StudieseDepression scale. If participants did not answer “rarely or none of the time” to these questions, they were defined as having exhaustion.19 Weakness was assessed by grip strength, and the cutoff point for weakness was 26 kg in men and 18 kg in women.19 Low physical activity was defined as the lowest 20% of leisure-time physical activity by sex.19 Slowness was assessed by comfortable gait speed, and the cutoff point for slowness was 1.0 m/s for men and women.19 Other Parameters Percentage of body fat was assessed by dual-energy x-ray absorptiometry (QDR-4500; Hologic, Marlborough, MA). Data regarding current smoking habits and medical history were assessed using selfcompleted questionnaires and were confirmed by a physician following a medical examination. The number of comorbidities was defined as the sum of a history of cerebrovascular disease, heart disease, cancer, diabetes, hypertension, dyslipidemia, osteoporosis, arthritis, anemia, dementia, and depression symptoms. The mean total caloric intake per day (kcal/d) was calculated from a 3-day dietary record.26 Education history was assessed using self-completed questionnaires. Statistical Analysis SAS 9.3 (SAS Institute Inc, Cary, NC) was used for all statistical analyses. P values <.05 were considered statistically significant. Data are presented as mean standard deviation. Cumulative data were analyzed using the generalized estimate equation (GEE). The number of steps and physical activity levels were modeled as dichotomized variables in GEE analyses. In this study, the cut-off value of the number of steps, LPA, and MVPA was 5000 steps/d, 40.3 minutes/d, and 7.5 minutes/d, respectively. The cut-off values of the number of steps and MVPA were associated with health-related quality of life among community-dwelling Japanese older adults.13 However, the cut-off value of LPA was not reported in that previous study. The daily 5000 steps and MVPA of 7.5 minutes were approximately equal to the 25th percentile of study subjects in this study. Thus, the cut-off value of LPA was defined as the 25th percentile of LPA (40.3 minutes/d). GEE models were used to determine the associations of physical activities with frailty using adjusted models with confounders. Model 1 was adjusted for follow-up year (continuous variable) and sex and age at baseline (years; continuous variable). Model 2 was further adjusted for follow-up year (continuous variable), sex, age, body fat (continuous variable), education (continuous variable),
A. Yuki et al. / JAMDA xxx (2019) 1e5 Table 1 Characteristics of Participants at Baseline Subjects (N ¼ 401)
Mean (SD) or n (%)
Women Age, y Frailty status Robust Prefrailty Number of steps/d Light-intensity physical activity, min/d Moderate- to vigorous-intensity physical activity, min/d Body fat, % Education, y Energy intake, kcal/d Current smoker Comorbidities Cerebrovascular disease Heart disease Cancer Diabetes Hypertension Dyslipidemia Osteoporosis Arthritis Anemia Dementia Depression
178 (44.4%) 71.1 (4.3) 170 231 7204.1 55.5 20.4
(42.4%) (57.6%) (3500.3) (22.8) (19.2)
26.6 10.6 2022.4 57 1.4 22 40 22 38 160 90 38 60 41 11 31
(6.8) (2.7) (395.8) (14.2%) (1.2) (5.5%) (10.0%) (5.5%) (9.5%) (39.9%) (22.4%) (9.5%) (15.0%) (10.2%) (2.7%) (7.7%)
SD, standard deviation.
current smoking (no, yes), energy intake (continuous variable), number of comorbidities (continuous variable), and frailty status (robust or prefrailty) at baseline. Model 2 was also used to determine the associations of physical activities with each frailty criterion. Results The mean (standard deviation) follow-up period was 4.2 (3.4) years. Table 1 presents the baseline characteristics of the 401 participants. The mean (range) number of steps, time of LPA, and time of MVPA of subjects were 7204.1 steps/d (627.6-22,870.4 steps/d), 55.5 minutes/d (6.4-154.6 minutes/d), and 20.4 minutes/ d (0.1-103.6 minutes/d), respectively. Table 2 shows the results of GEE to determine the associations of physical activities with frailty. Significant associations between subjects walking <5000 steps and frailty were noted in model 1 (P < .01) and model 2 (P < .05). Significant associations between frailty and Table 2 Longitudinal Relationship Between Physical Activity and Frailty Activity
Number of steps <5000 steps/d 5000 steps/d LPA (1.8-3.0 METs) <40.3 min/d 40.3 min/d MVPA (3.0 METs) <7.5 min/d 7.5 min/d
Cases
Model 1
Model 2
OR (95% CI)
OR (95% CI)
46/477 62/1310
2.09 (1.25-3.49)* 1.00 (Reference)
1.85 (1.10-3.11)y 1.00 (Reference)
37/433 71/1354
1.55 (0.93-2.60) 1.00 (Reference)
1.35 (0.82-2.25) 1.00 (Reference)
45/462 63/1325
2.07 (1.24-3.48)* 1.00 (Reference)
1.80 (1.05-3.09)y 1.00 (Reference)
Model 1 was adjusted for follow-up year (continuous variable) and sex and age at baseline (years; continuous variable). Model 2 was adjusted for follow-up year (continuous variable), sex, age, body fat (continuous variable), education (continuous variable), current smoking (no, yes), energy intake (continuous variable), number of comorbidities (continuous variable), and frailty status (robust or prefrailty) at baseline. Chi-square test. *P < .05. y P < .01.
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subjects with <7.5 minutes/d of MVPA were noted in model 1 (P < .01) and model 2 (P < .05). Modeling the number of steps as a continuous variable in model 2, the odds ratio (OR) (95% confidence interval [CI]) for development of frailty with an increase in 1000 steps was 0.92 (0.84-1.01; P ¼ .09). Modeling the time of LPA and MVPA as a continuous variable in model 2, the OR (95% CI) for a development of frailty with an increase in 10 minutes was 0.96 (0.82-1.11; P ¼ .57) and 0.83 (0.70-0.97; P < .05), respectively. The fully adjusted OR (95% CI) for the development of low activity in subjects walking <5000 steps daily and with <7.5 minutes of MVPA daily was 1.72 (1.12-2.64; P < .05) and 1.92 (1.26-2.92; P < .01), respectively. In addition, the fully adjusted OR (95% CI) for the development of slowness in subjects walking <5000 steps daily and with <7.5 minutes of MVPA daily was 2.01 (1.17-3.44; P < .05) and 3.19 (1.90-5.34; P < .0001), respectively. No other significant associations were noted between the frailty criteria and physical activity (data not shown). Discussion The present study demonstrated that daily steps and time of MVPA can predict physical frailty in older Japanese adults during a 10-year follow-up period. Both of these variables were objective values based on data records of accelerometers. These results are consistent with previous cross-sectional and randomized control trials that showed an association between sedentary lifestyle and frailty.3,14e16,27 In the present study, <5000 steps/d or MVPA of <7.5 minutes/d, which were the cutoff values for an impact on health-related quality of life, were associated with the development of frailty. In a study using the data of yearlong measurements of physical activity for older Japanese people, a higher level of physical activity was shown to be associated with a higher level of metabolic and physical health and lower health care costs in older Japanese adults.13,28 In particular, the cut-offs for physical health were 7000 steps/d or an MVPA of 15 minutes/d.29 A randomized control trial that used physical activity among older American adults to assess those with a high risk for mobility disability reported that the prevalence of frailty was decreased by walking (the intensity of training was gradually increased during the intervention period) at least 20 minutes/d.3 Another study that used the combination of walking (up to 20 minutes/d), strength, balance, and flexibility exercises also reported that the incidence of frailty among nonfrail participants for the first 6 months was lower in the group that participated in physical activity than in the group that underwent health education.27 The levels of physical activity associated with the development of frailty in the current study were lower than in these previous studies. The discrepancy between previous studies and this study might be caused by the difference in populations, particularly the mean age of the subjects, or in study designs, such as the difference between an observational study and an intervention study. Moreover, in this study, subjects who met the frailty definition at baseline were excluded. For older, nonfrail people, excessive physical activity might not be needed to prevent frailty. The lower mark for physical activity used in this study may contribute to interventions that encourage participation in physical activity to prevent frailty in old people. A time of MVPA of <7.5 minutes/d was significantly associated with the development of frailty. A previous study using an accelerometer for older Japanese adults showed that the reference value of 3 METs of physical activity for the maintenance of mental and physical health was 15 minutes/d.13 Our findings of an MVPA of 7.5 minutes/d (3.0 METs) to predict the development of frailty were consistent with those results. Interestingly, it is possible that physical activities with a higher intensity than walking, such as doing laundry, playing with animals, bicycling, and jogging,30,31 might contribute to the prevention of frailty even if the time engaged in MVPA is short.
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Although <5000 steps daily, which equals about 50 minutes of activity, was associated with the development of frailty, the results in this study also suggest that walking for more than 1 hour is not always associated with the prevention of frailty. Various daily activities with a higher intensity than walking may be suitable for the prevention of frailty and may allow for the development of different programs to help prevent frailty in older people. A significant association was observed between daily steps, MVPA, low physical activity, and development of slowness. The low activity and steps and MVPA might be closely related. In a longitudinal study with a 4-year follow-up, physical activity predicted the decline of gait speed.32 Similarly, slow gait speed was longitudinally associated with the development of disability in activities of daily living33,34 and the incidence of certified need for care in the longterm care insurance system in Japan.35 In this study, walking 5000 steps/d or an MVPA of 7.5 minutes/d appeared to contribute to the prevention of frailty. No significant association was observed between LPA and frailty development. The precise reasons for this observation are unknown, but activities with 1.8 to 2.9 METs include housework, a light-conditioning exercise, or light work in the standing position.30,31 Activities with 1.8 to 2.9 METs appear to lack locomotion, brisk movement, or an increase of heart rate. Therefore, absolute deficiency of stimulus by LPA might not prevent the development of frailty. The criteria of physical activity for health promotion in Japan recommend an increase in physical activity of 1500 steps/d or 10 minutes/d.36,37 In this study, a dose-response relationship between MVPA time and frailty development was observed. Increasing physical activity with as much locomotion as possible may contribute to the prevention of frailty. Further studies that focus on the cumulative effect of daily physical activity are necessary to determine additional activity factors that may promote better health in older adults. This study has several limitations. First, physical activity was recorded by a uniaxial accelerometer, not a triaxial accelerometer as was used in other recent studies. Second, lifestyle modifications of study subjects were not known. For example, medical episodes during the follow-up period might have decreased physical activity. An interest in well-being might have also led to a voluntary increase in physical activity. Third, the measuring period with the accelerometer was only 7 days. Finally, the generalizability of these findings to older adults in other countries cannot be confirmed. In particular, people in East Asian countries, including Japan, appear to walk more than people in other countries such as the United States or European countries.38 A study that measured MVPA time for Americans using an accelerometer reported that the mean MVPA time in men and women aged 60-69 years was 16.7 minutes/d and 12.4 minutes/d, respectively.22 The mean MVPA time in this study was 20.4 (19.2) minutes/d. It is not clear if 5000 steps/d or MVPA time of 7.5 minutes/d is enough stimulation to prevent frailty in older people with lower levels of physical activity than the population in this study. Conclusions and Implications In conclusion, this study examined the association between physical activity including the number of steps, LPA equivalent to <3.0 METs, and MVPA 3.0 METs as predictors of frailty development using 1787 cumulative data points from 401 community-dwelling older Japanese adults. The risk for developing frailty was substantially lower in older people walking 5000 steps/d or exercising 7.5 minutes/d at an intensity of 3.0 METs. Objective values associated with frailty development might contribute to the development of physical activity reference values for frailty prevention.
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