Article Text

Modelling the population-level impact of tai-chi on falls and fall-related injury among community-dwelling older people
1. Lesley Day1,
2. Caroline F Finch2,
3. James E Harrison3,
4. Effie Hoareau1,
5. Leonie Segal4,
6. Shahid Ullah2
1. 1Monash University Accident Research Centre, Melbourne, Australia
2. 2School of Human Movement and Sport Sciences, University of Ballarat, Ballarat, Australia
3. 3Research Centre for Injury Studies, Flinders University, Adelaide, Australia
4. 4University of South Australia, School of Nursing and Midwifery, Adelaide, Australia
1. Correspondence to Dr Lesley Day, Monash University Accident Research Centre, Clayton, Melbourne, Victoria 3800, Australia; lesley.day{at}monash.edu

## Abstract

Objective To model the population level impact of tai-chi on future rates of falls and fall-related injury in older people as a tool for policy development.

Design An epidemiological and economic model for estimating population-level effectiveness of tai-chi.

Setting Australia, 2009.

Patients or subjects Australian community-dwelling population aged 70+ years, ambulatory and without debilitating conditions or profound visual defects.

Intervention Group-based tai-chi, for 1 h twice weekly for 26 weeks, assuming no sustained effect beyond the intervention period.

Main outcome measure Total falls and fall-related hospitalisation prevented in 2009.

### Predicting the effect on fall-related hospital admissions

We used the tai-chi model outputs and national hospital records from 2002–6 (the most recent national data) to estimate the percentage reduction in the fall-related hospitalisation rate that could be expected in 2009. Using previously published methods,27 average annual age-specific fall-related hospitalisation rates for 2002–3 to 2005–6 were applied to the matching age groups in the 2009 population projections to obtain the 2009 expected fall-related hospitalisation count for people 65+ years. Although the tai-chi model output related to people 70+ years (the group to whom the trial results can be generalised), we calculated the impact on the hospitalisation rates for 65+ years, as this is the age group most often used in Australian setting policy targets and is therefore more relevant to local policy makers when assessing the potential for falls interventions to meet their targets. The number of hospitalisations prevented predicted by the tai-chi intervention model was subtracted from the total count, and the resulting percentage reduction in the falls hospitalisation rate was calculated.

## Results

In the base case scenario with 1.9% of the eligible population (n=31 998) taking up tai-chi, 5440 falls and 109 fall-related hospital admissions would be prevented (table 2). This equates to one fall prevented for approximately every six participants, one fall-related hospital admission averted for every 294 participants, and one fall-related hospital admission avoided per 50 falls prevented.

Table 2

Estimation of number of falls prevented and hospital admissions averted, tai-chi intervention model, Australian population 2009

Percentage changes relative to the base case scenario generated by changing the values of the input variables are shown in table 2. A negative value means that fewer falls and falls hospitalisations would be prevented compared with the base case. The variables with the greatest influence on the estimated number of falls prevented are the uptake rate and level of intervention effectiveness. The estimated proportion of falls resulting in hospital admission is an additional influence on the number of hospital admissions prevented.

The unit cost for the tai-chi intervention was $A750 per participant for the 26-week programme (table 3). This translated to costs of$A4414 (€3.013) and $A220 712 (€150 684) per prevented fall and hospital admission, respectively, in the base case scenario (table 4). Cost per fall prevented was determined by intervention effectiveness and intervention cost. Cost per hospital admission prevented was more sensitive to intervention effectiveness and the proportion of fallers admitted to hospital than the variation in intervention cost. The main influences on the total cost were the uptake rate and the variation in the intervention cost. Table 3 Implementation costs associated with twice weekly classes for 26 weeks, tai-chi intervention Table 4 Cost effectiveness, tai-chi intervention model, Australia 2009 The total cost of a 6-month tai-chi programme for community-dwelling older persons aged 70+ years, capable of participation, in Australia was estimated at$A24.01 million (€16.39 million), based on 31 998 participants (1.9% of all eligible persons). If participants contributed to class costs, government costs would be reduced by 21%, 35% and 70% for participant contributions per class of $A3,$A5 and $A10, respectively. We estimated that 75 754 fall-related hospitalisations among people aged 65+ would be expected in Australia in 2009. On the basis of our base case prediction of 109 fall-related hospital admissions averted, the annual fall-related hospital admission rate in 2009 could be expected to be reduced by 0.18%. Under the high hospitalisation rate assumption combined with the more effective intervention scenario, a 0.24% reduction in fall-related hospital admissions is predicted, while the less effective intervention scenario would produce a 0.10% reduction. ## Discussion This is the first published study to apply epidemiological and economic modelling to assess the population-level impact of a falls-prevention intervention among older people. It provides extensive methodological detail which could be readily applied to estimate the effect of falls interventions in other countries. The approach could also be applied to other injury issues where there is sufficient intervention evidence. We estimated that, if implemented in the eligible Australian population in 2009, a group-based tai-chi programme would prevent 5440 falls and 109 fall-related hospital admissions for a total cost of$A24.01 million. This equates to $A4414 and$A220 712 per fall and per fall-related hospital admission prevented, respectively. The estimated effect on the fall-related hospital admission rate for persons aged 65+ years is a 0.18% reduction.

Our study clearly shows that an intervention can be highly effective in a randomised trial, but have very little population-level impact. Group-based tai-chi is a relatively effective falls intervention in a controlled setting delivering a fall reduction of 37%.3 However, unless population-level uptake is considerably higher than the evidence-based rate used in our tai-chi model, this intervention will have only limited impact on population falls and fall-related hospital admission rates. Some among the eligible population would never take up tai-chi. This highlights the importance for policy of looking beyond RCT results to the population health context.

We have taken the conservative position of generalising the trial results to community-dwelling people aged 70+ years with similar fitness and mobility levels to the trial participants. The younger age group (60–69 years) may experience similar levels of falls reduction, but there is no firm evidence to support this contention. Certainly, tai-chi may be less effective among frailer older people.13

In defining the eligible population, we relied on estimates from a 2003 population survey.19 If the proportion of community-dwelling older people with restrictions in their core activities changed between 2003 and 2009, the number of eligible people would change accordingly, affecting the number of falls and falls hospitalisations prevented in the base case scenario and the total cost of programme delivery. The cost per fall and per fall hospital admission prevented would remain unchanged.

We have assumed that the size of the falls reduction reported in the Cochrane review,3 based on one Australian and three American studies, is generalisable to community-dwelling older Australians with similar fitness and mobility characteristics. In addition, we assumed that intervention compliance (ie, the proportion of classes attended by the participants, and the extent of practice between class sessions) would equal that achieved in the trials.13–16 Population-level compliance may actually be lower than that achieved in a research trial, resulting in a less effective intervention, with fewer falls and fall hospitalisations prevented.

We assumed that all willing eligible persons would take up the programme in the first year, and that it would not be repeated in subsequent years for the new cohort who would become eligible as they reach 70 years of age. We conservatively selected 6 months as the intervention effect period for the base case scenario, consistent with the follow-up periods in most of the trials.13–16 However, there is some evidence of effect beyond the 6-month period. In one trial, 66% of participants maintained tai-chi practice and sustained the falls reduction over 12 months.14 If this level of sustained effect was achieved in the base case scenario, ∼1.7 times as many falls and fall-related hospital admissions would be prevented for the same investment, with a flow-on effect on the hospital admission rate. The cost per fall and per fall-related hospital admission would be reduced by 30%.

There is a high degree of confidence in the other key assumptions. There is some evidence to support the assumption that falls reductions translate to the same level of effect on fall hospitalisations.28 In theory, an exercise programme might further reduce fall hospitalisations by improving bone strength to the point where fractures would be reduced in the event of a fall, so that fall hospitalisations would be reduced via two different mechanisms. However, it is unlikely that participation in a 26-week tai-chi programme could achieve such an improvement in bone strength. It is also unlikely that any control group activity in the trials would have had an effect on falls, although if it had, the effect on fall rates would be greater than our estimates.

Our study showed that investment of $A24.01 million in group-based tai-chi programmes in Australia would have a small effect on total falls and falls hospital admissions, reducing the fall-related admission rate by less than 0.5%. This would not, on its own, even curb the current average annual fall-related hospital admission rate increase of 2.5% for men and 1.1% for women.29 The annual cost of fall-related episodes of hospital care in Australia provides some context for the required level of investment. The most recent available estimate of this cost is$A566 million for 2003/4.27 An investment of $A24.01 million would be equivalent to 4.2% of the cost of fall-related episodes of hospital care in 2003/4. Comparison with other proven falls interventions would be useful in guiding policy towards the most cost-effective falls intervention for the population level. Additional relevant factors in preparing for widespread implementation of tai-chi for community-dwelling older people include sufficient appropriately trained tai-chi leaders and accessible venues. Implementation may be more difficult in rural and more remote areas because of a limited trained workforce, lack of critical mass required to make class groups viable, and fewer transport options. We estimated the effect of tai-chi on one health outcome: falls. Other health benefits include improvements in musculoskeletal function (strength, balance, flexibility), cardiorespiratory function (including blood pressure), glucose metabolism, body mass index, immune capacity, mental health and quality of life.30–33 Tai-chi could therefore affect key risk factors (physical inactivity, high body mass, high blood pressure) that explain considerable proportions of attributable health loss associated with cardiovascular disease, diabetes mellitus and, to a lesser extent, cancer.34 Anecdotal evidence suggested that most participants enjoyed tai-chi, generating direct ‘consumption’ benefits. Our study shows that, if participants were to contribute even$A5 towards the cost of a class, government costs would be reduced by 35%. Investment in tai-chi for older people is expected to deliver a range of health benefits and reduced health-related costs beyond those associated with falls prevention, thereby making the intervention more cost-effective at a population health level. Ideally the wider benefits would be incorporated into policy decisions.

## Conclusions

The translation of RCT results to the population level is possible and provides useful supplementary information for decision makers. Tai-chi programmes may present good value for falls-prevention resources, if the cost per participant can be substantially reduced compared with the cost estimates used here. We have found that, despite tai-chi representing an effective intervention, considerably higher population uptake than that observed in a recent trial would be required for a national roll-out of tai-chi to have a large effect on fall-related hospitalisation rates. This is not to say that investment in tai-chi is not worthwhile, given the potential for other health benefits and overall cost-effectiveness. This modelling approach, applied to other proven falls interventions, may assist in selecting the most cost-effective population-level falls-prevention portfolio for Australia and other countries.

### What is already known on this subject

• Reliable evidence shows that interventions, such as group-based tai-chi, can reduce falls among community-dwelling older people.

• Trial results rarely convey the effect that interventions may have at the population level.

• Modelling enables extrapolation of trial results to broader populations and assessment of the effect of variations in different key input variables on cost-effectiveness estimates.

• An approach for modelling the population-level effectiveness and cost-effectiveness of proven falls interventions to better guide decision-making with respect to policy and practice.

• Demonstration of the utility of an approach to estimating the population-level effect of one proven falls intervention—group-based tai-chi.

• Significant investment in, and high levels of population uptake of, tai-chi programmes would be required to produce meaningful reductions in the fall-related hospitalisation rates in Australia.

## Acknowledgments

We thank the following people who generously provided data for use in this project: Dr Alex Voukelatos, Sydney South West Area Health Service, Australia; Rob Maris, and Professor Steve Wolf, Emory University, USA. Soufiane Boufous, George Institute, Australia, provided advice on working with falls hospitalisation data. Clare Bradley, Flinders University, Australia, undertook the hospitalisation rate analyses.

## Footnotes

• Funding This project was funded through the Australian Government Department for Health and Ageing (Falls and Community Injury Grants Program). LD and CF were supported by National Health and Medical Research Council (NHMRC) Senior Research and Principal Research Fellowships, respectively. SU was supported by an Injury Trauma and Rehabilitation (ITR) Research Fellowship funded through a NHMRC Capacity Building Grant in Population Health.

• Competing interests None.

• Provenance and peer review Not commissioned; externally peer reviewed.