Aerobic fitness, physical function and falls among older people : a prospective study
Bell, Rebecca A. (2008) Aerobic fitness, physical function and falls among older people : a prospective study. PhD thesis, Queensland University of Technology.
Falls in people aged over 65 years account for the largest proportion of all injury-related deaths and hospitalisations within Australia. Falls contributed to 1,000 deaths and 50,000 hospitalisations in older people during 1998 (Commonwealth Department of Health and Aged Care 2001). It has been predicted that by 2016, 16% of the Australian population will be aged over 65 years (Australian Bureau of Statistics 1999) placing considerable pressure on the health care system. Furthermore, prospective studies have shown that 30-50% of people aged 65 years and over, will experience a fall (Tinetti et al. 1988b; Campbell et al. 1989; Lord et al. 1994b; Hill 1999; Brauer et al. 2000; Stalenhoef et al. 2002) and this figure increases exponentially with age (Lord et al. 1994b).
Many physiological falls risk factors have been established including reduced leg strength, poor balance, impaired vision, slowed reaction time and proprioception deficits. However, little research has been conducted to determine whether performance on aerobic fitness tasks is also a physiological falls risk factor. Aerobic fitness has previously been related to an individual's ability to perform activities of daily living, which in turn has been linked to falls. It was therefore proposed that aerobic fitness might also be a risk factor for falls among community dwelling older people.
This research aimed to provide clinical evidence to inform public health practice. This thesis comprised of four objectives: the first to find suitable measures of aerobic fitness for older people; the second investigated relationships between existing clinical tests and future falls; the third explored relationships between aerobic fitness tests and future falls; the final objective was to examine the independent relationships between falls and clinical and physiological characteristics. The participants were recruited through a random sample from the local electoral roll, with an average age of 73 ±6 years. Of the 87 participants who completed the prospective component of the study, 37% were male and 63% were female. Sixty-three participants (65%) reported no previous falls, 19 (20%) reported a single fall, and 16 (15%) reported two or more falls in the previous 12 months.
The first objective required participants recruited from the community to take part in submaximal and maximal fitness tests in order to find suitable measures of aerobic fitness. A further objective was to determine whether older people were able to fulfil the 'standard' criteria for completion of a maximum oxygen consumption test. The measures used in this research included: maximum oxygen consumption, peak oxygen consumption, ventilatory threshold, oxygen uptake kinetics, oxygen deficit, efficiencies, oxygen consumption at zero, 30 and 50 watts, predicted max and Six-Minute Walk Test distance. Only weak relationships were observed between submaximal aerobic measures and peak oxygen consumption. Furthermore, only 54% of participants were able to fulfil the criteria to complete a test of maximum oxygen consumption, indicating it was not a suitable measure for use among a sample of community dwelling older people. Therefore submaximal aerobic variables were used in the following chapters.
The second objective investigated the relationship between clinical measures and falls among older people and was carried out to enable comparisons between the population in this study and those described in the literature. This research found that the Timed Up and Go (TUG) test was the most sensitive of all clinical tests (including the Berg Balance Scale, Function Reach, Performance Oriented Mobility Assessment and Physiological Profile Assessment) for the assessment of future falls. The TUG requires participants to stand up, walk 3m, turn, walk back, and sit down. Time taken to complete the test is the recorded value. For this study, a cut-off value of 7-seconds was established, above which individuals were at increased risk of falls. Previous research suggested cut-off times of over 10s were appropriate for older people. However, this is the first study to assess falls prospectively and definitively find that the TUG can discriminate between future fallers and non-fallers.
This research also investigated the differences in falls risk factors for functionally different subsamples, as defined by their ability to undertake and complete the cycle test. The participants who could complete the test had significantly better balance ability and strength than those unable to undertake or complete the cycle test. However, this inability to undertake or complete the cycle test was not itself a predictor of future falls. These two groups also differed in the relationships between clinical test results and falls risk. Participants in the no-cycle group had very similar results to that of the entire cohort. Even after adjustment for age, the TUG, foot and hand reaction times and knee flexion strength were all performed better by non-fallers than fallers. However, none of these differed between fallers and non-fallers for participants in the cycle group. This group had better balance ability and strength than the no-cycle group. These results indicated that the cycle group differed from the no-cycle group and the entire sample, further indicating that factors other than the physiological variables measured in this research influence falls risk in strong participants with good balance ability.
Similar results were reported when aerobic tests and falls were investigated in the third objective. In the whole sample, the fallers walked significantly less distance than non-fallers for the 6-MWT. Similar results were found for participants in the no-cycle group but not the cycle group. All participants were able to complete the Six-Minute Walk Test (6-MWT) although only 74% were able to undertake and complete the cycle test.
The fourth objective was to consider all measures from the previous chapters as potential predictors of falls. The variables most predictive of future falls were the TUG and having experienced one or more falls in the previous 12 months. As a result they could be used as screening tools for the identification of high-risk fallers who require referral for further assessment. This could be completed by a General Practitioner or Practice Nurse, which would ensure that screening is being undertaken in the wider population. If the patient is at high risk they should be referred for falls risk factor assessment to determine an optimal tailored intervention to reduce future falls. Low risk patients should be referred for preventive evidence-based activities. These steps can potentially improve quality of life for individuals, and if effective in preventing future falls, will result in reduced costs to the individual and the Australian public.
The results of this work demonstrate that the best screening tests are simple tasks like the TUG and asking an individual if they have experienced a fall in the last 12 months. This research also found that strong, mobile older people who could undertake and complete a submaximal cycle ergometer test, still experienced falls in the following 12 months, although the causes of this are currently unknown. This research showed that physiological falls risk factors are less relevant as these highly functional older people do not have physiological deficits. However, this research found that the 6-MWT showed promise as a predictor of falls in a group who could not complete a submaximal cycle ergometer test, who had lower strength, balance and functional fitness scores than a group who could complete this cycle test. The results showed that physiological falls risk factors are still very important for older people with lower physical abilities, and this is where aerobic fitness may still be related to falls. While the association between aerobic fitness and falls remains unclear, these are novel and provocative findings highlighting the need for future falls risk investigations to consider aerobic fitness as a contributing factor.
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|Item Type:||QUT Thesis (PhD)|
|Supervisor:||Newman, Beth, Kerr, Graham, Worringham, Charles, & Lord, Stephen|
|Keywords:||falls risk assessment, screening, predictors, maximum oxygen uptake, submaximal fitness measures, six-minute walk test, clinical tests|
|Department:||Faculty of Health|
|Institution:||Queensland University of Technology|
|Copyright Owner:||Copyright Rebecca Anne Roodveldt Bell|
|Deposited On:||03 Dec 2008 04:07|
|Last Modified:||28 Oct 2011 19:50|
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