Website Edition: December 2009/January 2010

Editor's Choice Article and Review

Movement Disorders
Volume 24, Issue 13, Pages 1934-1940
Published Online: 11 August 2009

Physical assessment as a predictor of mortality in people with Parkinson's disease: A study over 7 years
William K. Gray, PhD¹, Anthony Hildreth, MPhil¹, Julie A. Bilclough, MSc², Brian H. Wood, MD², Katherine Baker, PhD¹, Richard W. Walker, MD² *

¹School of Health, Community and Education Studies, University of Northumbria, Coach Lane Campus, Newcastle-upon-Tyne, United Kingdom
²Department of Medicine, North Tyneside General Hospital, North Shields, Tyne and Wear, United Kingdom

E-mail: Richard W. Walker (richard.walker@nhct.nhs.uk)

*Correspondence to Richard W. Walker, Department of Medicine, North Tyneside General Hospital, Rake Lane, North Shields, Tyne and Wear, NE29 8NH United Kingdom

Potential conflict of interest: None reported.

Funded by:
Northumbria Healthcare NHS Foundation Trust
Parkinson's Disease Society
University of Northumbria
U.K. National Health Service

Abstract

The primary aim of this study was to ascertain whether a battery of physical function measures in a Parkinson's disease (PD) patient cohort predicted mortality status at 7-year follow-up. Secondary aims were establishing which specific tests were the most useful, and whether PD phenotype was a predictor. A retrospective correlation design was used in this study. A cohort of 109 PD patients underwent baseline physiotherapy assessment of gait, balance, posture, muscle strength, and ability to change postural set. We compared mortality status at 7-year follow-up and baseline physical assessment tests. Tinetti gait and balance scores, UPDRS score, 10-m walk test (time, velocity, and number of strides), posture in standing, lying to sitting, sitting to standing, getting up from floor assessments, and time to ascend and descend four steps were found to be statistically significant physical predictors of mortality at 7-year follow-up. In addition, age, sex, and mini-mental state examination were significant nonphysical predictors of mortality. Using Cox regression, a survival model was constructed with age, sex, and Tinetti gait score as independent predictors of mortality. The results of this study suggest that there is a link between reduced physical function and an increased mortality risk in PD populations.

© 2009 Movement Disorder Society

Received: 19 January 2009; Revised: 30 March 2009; Accepted: 4 April 2009

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Podcast Summary and Review by Dr. Dudley O'Sullivan, AM, MBBS, FRACP, Emeritus Consultant Neurologist, Neurosciences Department, St Vincent's Hospital, Darlinghurst NSW Australia

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The primary function of the above article titled "Physical assessment as a predictor of mortality in people with Parkinson's disease, a study over 7 years" was to ascertain whether a battery of physical function measures in Parkinson's disease (P.D), patient cohort predicted mortality status at a 7-year follow up.

The paper published in Movement Disorders assesses 109 patients with P.D, 52 men and 57 women, whose ages at the start of the study in January 2000, were 74.0 for men, and 75.3 for women. All patients were assessed regarding physical function and ability during a 30-minute objective and subjective assessment by a single senior physiotherapist, who had a special interest in P.D. These tests included 10-M walk test, Tinetti balance and gait assessment, Hoen Yahr rating and the Unified Parkinson Disease Rating Scale (UPDRS) assessment. All patients were followed up for 7 years; 46 (42.2%) had died by the 31st December 2006. The average age at death was 79.8 years for men and 82.4 years for women. More men (28) had died during the 7-year follow up period compared with only 18 women. This was found to be statistically significant, although the numbers were small.

The study concluded that a link between diminished performance in commonly used tests of physical function, in particular, measures of gait, balance, posture, ability to climb and descend stairs, and postural instability, had an increased risk of mortality among P.D patients. Furthermore, age, sex and Tinetti gait scores are independent predictors of mortality. Also, there was in the study those patients who had tremor predominant disease, who seemed to live longer.

The appraisal of this study deserves the following comments:

1. The cohort in this study was significantly older than other published studies on long-term follow up in patients with P.D. There were also a higher proportion of women.

2. In the discussion, authors mention that age, sex and the total MMSE were the only predictable variables that correlate highly with mortality stated at 7-year follow up that were not directly measuring physical function. It is well known that the non-dopaminergic manifestations of this disease, especially cognitive decline and impaired balance with falls, are major factors that appear to predict increased mortality in patients with Parkinson's disease.

3. One small criticism of the paper is that the tests of physical function were performed over a 30-minute period. In table 1 this included a significant list of physical assessments as outlined in that particular table and I would think this was a fairly brief period time in which to make such an assessment. All patients were assessed only in the on state. The UPDRS scores had a maximum of 64 and minimum of 8. With a maximum of 64 and a range of 56 this would indicate that the cohort of patients had quite severe disease.

4. Although speech, chewing and swallowing difficulties would have been assessed in UPDRS scores, it would have been of value if comments were made to have these aspects of the disease assessed regarding mortality.

5. With regards to the cause of death in the cohort of patients, they state that 46 patients in the study were deceased by December 2006; 21, i.e. 46%, had pneumonia or chest infection listed as primary cause of death on the death certificate. It would be of value to have known of the remaining cohort who died, the cause of death. Was it attributable to P.D, or was is related to other factors such as myocardial infarction, or even as a result of falls perhaps causing subdural haematoma? They also mention there seemed to be a reduction in the mortality rate of those patients who had predominant tremor, rather than the akinetic rigid form of the disease. However, Andrew Lees's group from the National Hospital, Queen Square in London, has recently published a patient in Brain, where they studied the brains of 200 patients who had died of P.D, and who were pathologically proven to have P.D. They found there was no difference in the mortality between those patients with tremor dominant disease or with the akinetic rigid form.

6. Finally, the paper does clearly establish however, that physical impairment, especially impaired balance, gait disorder and posture instability, i.e. the midline or axial manifestation of this disease, are poor prognostic features. Unfortunately, the above manifestations are poorly levodopa responsive. Whether addressing these issues in the long-term will reduce mortality, will have to await further studies.

About Dr. O'Sullivan
Dudley J O'Sullivan AM. MBBS, FRACP, is Emeritus Consultant Physician in Neurology, St Vincent's Hospital, Darlinghurst, Sydney, NSW, Australia.

He has always been interested in P.D and movement disorders and with Dr Mariese Hely and Professor John Morris, et al, they established the Sydney Multicentre Study of Parkinson's disease and followed the progression and mortality of these patients over 10 years, and more recently, Dr Mariese Hely has published the mortality of this group over a 20-year follow up. The group was initially established in the 1980s.

As a result of his interest in Parkinson's disease, after discussion with the Sydney Multicentre Study group and the introduction of deep brain stimulation surgery for Parkinson's disease, it was decided by the group that deep brain stimulation surgery should be performed at St Vincent's Hospital. This was commenced in 1994 with his neurosurgical colleague, Dr Malcolm Pell, under the guidance of Professor Alim Benabid. Initially, this was for tremor patients using DBS of the VIM thalamic nucleus. In 1997, again under the supervision of Professor Alim Benabid, they embarked on bilateral STN stimulation for more advanced Parkinson's disease patients. This programme is still continuing at St Vincent's Hospital. Dr Malcolm Pell and Dr O'Sullivan have been instigators in training other units in Asia in the technique of DBS surgery and the assessment of patients.