Neurorehabilitation and Neural Repair http://nnr.sagepub.com/
The Relative Contribution of Physical and Cognitive Fall Risk Factors in People With Parkinson's Disease: A Large Prospective Cohort Study Serene S. Paul, Catherine Sherrington, Colleen G. Canning, Victor S. C. Fung, Jacqueline C. T. Close and Stephen R. Lord Neurorehabil Neural Repair 2014 28: 282 originally published online 15 November 2013 DOI: 10.1177/1545968313508470 The online version of this article can be found at: http://nnr.sagepub.com/content/28/3/282
Published by: http://www.sagepublications.com
On behalf of:
American Society of Neurorehabilitation
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Downloaded from nnr.sagepub.com at University of Birmingham on October 30, 2014
508470
research-article2013
NNRXXX10.1177/1545968313508470Neurorehabilitation and Neural RepairPaul et al.
Clinical Research Article
The Relative Contribution of Physical and Cognitive Fall Risk Factors in People With Parkinson’s Disease: A Large Prospective Cohort Study
Neurorehabilitation and Neural Repair 2014, Vol. 28(3) 282–290 © The Author(s) 2013 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1545968313508470 nnr.sagepub.com
Serene S. Paul, PhD1, Catherine Sherrington, PhD2, Colleen G. Canning, PhD1, Victor S. C. Fung, PhD1,3, Jacqueline C. T. Close, MD4,5, and Stephen R. Lord, PhD, DSc5
Abstract Background. In order to develop multifaceted fall prevention strategies for people with Parkinson’s disease (PD), greater understanding of the impact of physical and cognitive performance on falls is required. Objective. We aimed to identify the relative contribution of a comprehensive range of physical and cognitive risk factors to prospectively-measured falls in a large sample of people with PD and develop an explanatory multivariate fall risk model in this group. Methods. Measures of PD signs and symptoms, freezing of gait, balance, mobility, proprioception, leg muscle strength, and cognition were collected on 205 community-dwelling people with PD. Falls were monitored prospectively for 6 months using falls diaries. Results. A total of 120 participants (59%) fell during follow-up. Freezing of gait (P < .001), dyskinesia (P = .02), impaired anticipatory and reactive balance (P < .001), impaired cognition (P = .002), reduced leg muscle strength (P = .006), and reduced proprioception (P = .04) were significantly associated with future falls in univariate analyses. Freezing of gait (risk ratio [RR] = 1.03, 95% confidence interval [CI] = 1.00-1.05, P = .02), impaired anticipatory (RR = 1.01, 95% CI = 1.001.02, P = .03) and reactive (RR = 1.26, 95% CI = 1.01-1.58, P = .04) balance, and impaired orientation (RR = 1.28, 95% CI = 1.01-1.62, P = .04) maintained significant associations with falls in multivariate analysis. Conclusion. The study findings elucidate important physical and cognitive determinants of falls in people with PD and may assist in developing efficacious fall prevention strategies for this high-risk group. Keywords Parkinson’s disease, accidental falls, risk factors, postural balance, cognition
Introduction Falls are a significant problem for people with Parkinson’s disease (PD), with fall rates double1 that of communitydwelling older people without neurological disease.2,3 Many falls experienced by people with PD result in injury4,5 and require costly health care. It is well known that previous falls1,6-8 are a strong predictor of future falls in people with PD. Several studies have identified a range of factors that are associated with an increased risk of falls in people with PD, such as impaired balance,5,6,9 impaired mobility,5,9 freezing of gait,5,9 decreased muscle strength,5,9 impaired cognition,4-6 and disease severity,4-7,9 but the relative contribution of these risk factors to falls is unclear. Other risk factors such as multiple drug use, depression, orthostatic hypotension, and limitations with daily activities have been proposed but do not show a consistent association with increased fall risk in people with PD.1,4,5,9-11 Understanding which risk factors are important in determining overall fall risk has the benefit of allowing clinicians
to target and prioritize interventions. An understanding as to whether the underlying cause of the impairment is remediable is also important as again it will determine whether an intervention is put in place to address the risk factor (eg, cataract removal to correct the associated visual impairment) or minimize the impact of the identified deficit (eg, provision of mobility aids for people with severe balance problems). This is an important contrast to other variables such as “past falls” that have been used in previous 1
The University of Sydney, Sydney, New South Wales, Australia The George Institute for Global Health, Sydney, New South Wales, Australia 3 Westmead Hospital, Sydney, New South Wales, Australia 4 Prince of Wales Clinical School, University of New South Wales, Sydney, New South Wales, Australia 5 Neuroscience Research Australia, Sydney, New South Wales, Australia 2
Corresponding Author: Serene S. Paul, Faculty of Health Sciences, The University of Sydney, PO Box 170, Lidcombe New South Wales 1825, Australia. Email: [email protected]
Downloaded from nnr.sagepub.com at University of Birmingham on October 30, 2014
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Paul et al. prediction models, that is, although predictive, such marker variables provide little insight into why future falls occur and do not guide intervention strategies. To gain a greater understanding of the causes of falls, some studies in the general older population have investigated possible physical and cognitive risk factors that may explain mechanisms underlying falls.12,13 To date, only 2 prospective studies of falls undertaken in people with PD have included both physical and cognitive factors.5,14 One study found carer-rated cognitive impairment and freezing of gait to be important explanatory fall risk factors but this study contained only a small sample size (n = 52).14 The other study5 included a larger sample (113 participants) and identified freezing of gait, poor balance, reduced muscle strength, impaired executive functioning, and abnormal posture as independent risk factors for falls in a multivariate explanatory model. As some of the impairments identified above are amenable to intervention, these studies provide valuable information for informing fall prevention initiatives in people with PD. Given that only 2 studies have investigated potentially remediable physical and cognitive fall risk factors (without including prior falls in the models),5,14 further work is required to confirm such findings in large external samples and identify possible additional important explanatory fall risk factors. Therefore, this study aimed to identify the relative contribution of a comprehensive range of physical and cognitive factors to future falls in a sample of over 200 people with PD. We hypothesized that both physical and cognitive factors would make independent contributions to overall fall risk in people with PD and that these important fall risk factors would be potentially amenable to intervention.
Methods Participants A total of 205 participants, recruited from Parkinson’s support groups and private neurology clinics, participated in this study: 133 were drawn from the control groups of 2 randomized controlled trials assessing exercise interventions15,16 and the remainder comprised participants who did not meet the inclusion criteria for the randomized controlled trials or chose not to participate in them. The eligibility criteria for this study were as follows: having idiopathic PD as confirmed by a medical practitioner, older than 40 years, and able to walk independently with or without an aid. Participants were excluded if they had significant cognitive impairment (Mini Mental State Examination [MMSE]17 score
The Relative Contribution of Physical and Cognitive Fall Risk Factors in People With Parkinson's Disease: A Large Prospective Cohort Study Serene S. Paul, Catherine Sherrington, Colleen G. Canning, Victor S. C. Fung, Jacqueline C. T. Close and Stephen R. Lord Neurorehabil Neural Repair 2014 28: 282 originally published online 15 November 2013 DOI: 10.1177/1545968313508470 The online version of this article can be found at: http://nnr.sagepub.com/content/28/3/282
Published by: http://www.sagepublications.com
On behalf of:
American Society of Neurorehabilitation
Additional services and information for Neurorehabilitation and Neural Repair can be found at: Email Alerts: http://nnr.sagepub.com/cgi/alerts Subscriptions: http://nnr.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> Version of Record - Feb 11, 2014 OnlineFirst Version of Record - Nov 15, 2013 What is This?
Downloaded from nnr.sagepub.com at University of Birmingham on October 30, 2014
508470
research-article2013
NNRXXX10.1177/1545968313508470Neurorehabilitation and Neural RepairPaul et al.
Clinical Research Article
The Relative Contribution of Physical and Cognitive Fall Risk Factors in People With Parkinson’s Disease: A Large Prospective Cohort Study
Neurorehabilitation and Neural Repair 2014, Vol. 28(3) 282–290 © The Author(s) 2013 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1545968313508470 nnr.sagepub.com
Serene S. Paul, PhD1, Catherine Sherrington, PhD2, Colleen G. Canning, PhD1, Victor S. C. Fung, PhD1,3, Jacqueline C. T. Close, MD4,5, and Stephen R. Lord, PhD, DSc5
Abstract Background. In order to develop multifaceted fall prevention strategies for people with Parkinson’s disease (PD), greater understanding of the impact of physical and cognitive performance on falls is required. Objective. We aimed to identify the relative contribution of a comprehensive range of physical and cognitive risk factors to prospectively-measured falls in a large sample of people with PD and develop an explanatory multivariate fall risk model in this group. Methods. Measures of PD signs and symptoms, freezing of gait, balance, mobility, proprioception, leg muscle strength, and cognition were collected on 205 community-dwelling people with PD. Falls were monitored prospectively for 6 months using falls diaries. Results. A total of 120 participants (59%) fell during follow-up. Freezing of gait (P < .001), dyskinesia (P = .02), impaired anticipatory and reactive balance (P < .001), impaired cognition (P = .002), reduced leg muscle strength (P = .006), and reduced proprioception (P = .04) were significantly associated with future falls in univariate analyses. Freezing of gait (risk ratio [RR] = 1.03, 95% confidence interval [CI] = 1.00-1.05, P = .02), impaired anticipatory (RR = 1.01, 95% CI = 1.001.02, P = .03) and reactive (RR = 1.26, 95% CI = 1.01-1.58, P = .04) balance, and impaired orientation (RR = 1.28, 95% CI = 1.01-1.62, P = .04) maintained significant associations with falls in multivariate analysis. Conclusion. The study findings elucidate important physical and cognitive determinants of falls in people with PD and may assist in developing efficacious fall prevention strategies for this high-risk group. Keywords Parkinson’s disease, accidental falls, risk factors, postural balance, cognition
Introduction Falls are a significant problem for people with Parkinson’s disease (PD), with fall rates double1 that of communitydwelling older people without neurological disease.2,3 Many falls experienced by people with PD result in injury4,5 and require costly health care. It is well known that previous falls1,6-8 are a strong predictor of future falls in people with PD. Several studies have identified a range of factors that are associated with an increased risk of falls in people with PD, such as impaired balance,5,6,9 impaired mobility,5,9 freezing of gait,5,9 decreased muscle strength,5,9 impaired cognition,4-6 and disease severity,4-7,9 but the relative contribution of these risk factors to falls is unclear. Other risk factors such as multiple drug use, depression, orthostatic hypotension, and limitations with daily activities have been proposed but do not show a consistent association with increased fall risk in people with PD.1,4,5,9-11 Understanding which risk factors are important in determining overall fall risk has the benefit of allowing clinicians
to target and prioritize interventions. An understanding as to whether the underlying cause of the impairment is remediable is also important as again it will determine whether an intervention is put in place to address the risk factor (eg, cataract removal to correct the associated visual impairment) or minimize the impact of the identified deficit (eg, provision of mobility aids for people with severe balance problems). This is an important contrast to other variables such as “past falls” that have been used in previous 1
The University of Sydney, Sydney, New South Wales, Australia The George Institute for Global Health, Sydney, New South Wales, Australia 3 Westmead Hospital, Sydney, New South Wales, Australia 4 Prince of Wales Clinical School, University of New South Wales, Sydney, New South Wales, Australia 5 Neuroscience Research Australia, Sydney, New South Wales, Australia 2
Corresponding Author: Serene S. Paul, Faculty of Health Sciences, The University of Sydney, PO Box 170, Lidcombe New South Wales 1825, Australia. Email: [email protected]
Downloaded from nnr.sagepub.com at University of Birmingham on October 30, 2014
283
Paul et al. prediction models, that is, although predictive, such marker variables provide little insight into why future falls occur and do not guide intervention strategies. To gain a greater understanding of the causes of falls, some studies in the general older population have investigated possible physical and cognitive risk factors that may explain mechanisms underlying falls.12,13 To date, only 2 prospective studies of falls undertaken in people with PD have included both physical and cognitive factors.5,14 One study found carer-rated cognitive impairment and freezing of gait to be important explanatory fall risk factors but this study contained only a small sample size (n = 52).14 The other study5 included a larger sample (113 participants) and identified freezing of gait, poor balance, reduced muscle strength, impaired executive functioning, and abnormal posture as independent risk factors for falls in a multivariate explanatory model. As some of the impairments identified above are amenable to intervention, these studies provide valuable information for informing fall prevention initiatives in people with PD. Given that only 2 studies have investigated potentially remediable physical and cognitive fall risk factors (without including prior falls in the models),5,14 further work is required to confirm such findings in large external samples and identify possible additional important explanatory fall risk factors. Therefore, this study aimed to identify the relative contribution of a comprehensive range of physical and cognitive factors to future falls in a sample of over 200 people with PD. We hypothesized that both physical and cognitive factors would make independent contributions to overall fall risk in people with PD and that these important fall risk factors would be potentially amenable to intervention.
Methods Participants A total of 205 participants, recruited from Parkinson’s support groups and private neurology clinics, participated in this study: 133 were drawn from the control groups of 2 randomized controlled trials assessing exercise interventions15,16 and the remainder comprised participants who did not meet the inclusion criteria for the randomized controlled trials or chose not to participate in them. The eligibility criteria for this study were as follows: having idiopathic PD as confirmed by a medical practitioner, older than 40 years, and able to walk independently with or without an aid. Participants were excluded if they had significant cognitive impairment (Mini Mental State Examination [MMSE]17 score
