Journal of the New Zealand Medical Association, 17-December-2004, Vol 117 No 1207
Cost-effectiveness of physical activity counselling in general practice
Raina Elley, Ngaire Kerse, Bruce Arroll, Boyd Swinburn, Toni Ashton, Elizabeth Robinson
There is now substantial epidemiological evidence to implicate a sedentary lifestyle as a risk factor for obesity, diabetes, cardiovascular disease, depression, bowel and breast cancer, and various other disease states.1–4 Existing evidence suggests that at least 30 minutes of moderate activity on most days of the week is associated with significant health gains and has led to major position statements such as the 1996 US Surgeon General’s report on physical activity and health.4
In New Zealand, one-third of adults do not undertake the recommended 2½ hours of moderate-intensity physical activity per week.5 As a result, the Hillary Commission developed the Green Prescription physical activity counselling programme for New Zealand primary healthcare. A randomised controlled trial to assess the effectiveness of the programme in the Waikato region found that the programme was effective in increasing physical activity and improving quality of life over a 12-month period.6 However, the cost-effectiveness of the intervention was not known.
The aim of this study was to calculate the incremental cost-effectiveness of the Green Prescription programme in increasing physical activity compared with ‘usual care’ in general practice, and to compare this with other community-based physical activity interventions reported in the literature.
The cost-effectiveness analysis of the Green Prescription programme was incorporated prospectively into a cluster randomised controlled trial undertaken from mid-2000 to mid-2002.6 General practices in the Waikato region of New Zealand were randomised to give the Green Prescription or ‘usual care’ to patients enrolled in the study. Baseline and 12-month follow-up measurements were taken at each practice by research staff. The cost-effectiveness analysis was undertaken from health funders’ and societal perspectives. The Waikato Ethics Committee approved the study in 1999.
Consecutive 40 to 79 year-old patients were screened at the reception area of 42 rural and urban general practices over a 5-day period. Those not achieving the recommended 2½ hours of at least moderate activity per week were invited to participate in a study involving a lifestyle intervention.
Study participants from intervention practices prompted the general practitioner or nurse to give verbal advice to increase physical activity with activity goals written on a Green Prescription. Patients from control practices received usual care. The Green Prescription was then faxed to exercise specialists in Sports Foundations who provided telephone support on three occasions over the following three months to each intervention patient and sent written material including newsletters.
Primary outcome measures in the clinical trial were change in leisure-time physical activity, total energy expenditure, quality of life (using the SF36 scales), 4-year coronary heart disease risk, and systolic and diastolic blood pressure. A post-hoc analysis comparing the proportion of participants that achieved 2.5 hours of leisure activity was carried out to allow comparison with previous studies carried out in primary care.7
Primary outcomes measured for the cost-effectiveness study were the incremental cost of change in self-reported physical activity over 12 months. These outcomes included the cost per total energy expenditure gained, the cost per leisure moderate- and vigorous-intensity energy expenditure gained, and the incremental cost of moving one additional ‘sedentary’ person into the ‘active’ category (achieving 2½ hours of at least moderate-intensity leisure activity per week).
Costs—Green Prescription programme development costs incurred in previous years were obtained from the developers of the programme, the Hillary Commission, and were adjusted for inflation using the December consumer price index from each corresponding year compared with that of December 2001.8 A discount rate of 5% was used to calculate present equivalent values of programme costs from 1996 to 2001.9
Programme delivery costs included general practitioner and practice nurse time, Sports Foundation exercise specialists, and Green Prescription resources. Delivery costs within the general practice were estimated using usual consultation charges for participating practices, national award rates for practice nurses, and the time, estimated as 7 minutes by general practitioners and 13 minutes by practice nurses, for programme delivery.6 Charges for each general practice in the region were obtained at baseline and average charges calculated for each consultation type.
Actual regional Sports Foundation personnel and overhead costs associated with the programme were obtained from the Sports Foundation’s accounting department for the year 2001/2002. Average wage costs rather than marginal costs were used as the exercise specialists were permanent staff of the Sports Foundation.
Offset cost—Self-reported costs to the individual associated with exercise were identified by study participants in a 12-month follow-up questionnaire and included exercise equipment purchased, sports club or exercise group subscriptions, travel expenses to and from exercise, and any other costs associated with exercise over the 12 months of the study.
Costs associated with primary and secondary healthcare utilisation and costs of time off work were also recorded. Primary healthcare offset costs were calculated for each participant for the 12 months prior to study enrolment and compared with the 12 months after study enrolment. Actual number and type of general practice consultations were obtained from practice records. Actual government subsidies for each type of consultation were used and were adjusted for inflation.
Patient charges and subsidies vary. Average patient part-charges of participating practices were used for consultations of non-subsidised patients (A3) (NZ$35) and low-income (A1) or high-user patients (AZ) (NZ$20), and for accident-related consultations NZ($10). Government subsidies for each consultation were NZ$15 for A1 and AZ visits, and NZ$26 for all accident-related visits. Numbers of accident-related visits to physiotherapists, chiropractors, and osteopaths were obtained from patient questionnaires. These visits were subsidised at a rate of NZ$19 per visit, with an average patient surcharge of NZ$10.
Secondary care costs were established using each participant’s national health index, a unique identifier in primary and secondary healthcare allowing tracking of individual’s health care utilisation. Actual hospital inpatient, outpatient, and investigation costs for each patient from all public regional and base hospitals were obtained from the local district health board for the year prior to and the year following each patient’s enrolment in the study. Costs for private hospital-use could not be obtained. However, self-reported private hospital admission-rates were recorded.
To calculate the cost of loss of productivity due to illness and accident for the year prior to baseline compared with the year after baseline, the change in the number of days of illness- and accident-related leave taken were obtained by self-report. The average wage for the June quarter from wages, salary, and self-employment for those in paid employment was NZ$121.80/day for 2000 and NZ$128.20/day for 2001.10
All costs were adjusted for inflation using the 2001/2000 consumer price index ratio to calculate the incremental change. All costs are reported as New Zealand dollars. Where comparisons with programmes from the United States or the United Kingdom were carried out, values were converted to the New Zealand dollar according to the exchange rate of December 2001.11
Total setup and programme administration costs were obtained to calculate programme cost per patient. Actual offset costs of primary and secondary healthcare utilisation, personal expenditure, and productivity changes were collected wherever possible. The differences in change in offset costs to the patient and health funder for intervention patients compared with control patients, with 95% confidence intervals, were calculated using a random effects generalised least squares regression model, where the general practice was entered as the clustering variable in STATA version 7.0.
Cost-effectiveness ratios were obtained by calculating programme costs per activity gain from a programme-funder perspective. These ratios were compared with those from other physical activity interventions reported in the literature. Sensitivity analyses were conducted using the confidence intervals for calculated physical activity gains as the relevant range.7,12
All analyses were carried out using an intention-to-treat approach, where no change from baseline was assumed in those who did not attend follow-up, except personal costs associated with exercise, where costs were assumed to be the mean of those in the equivalent group.
Table 1 shows the characteristics of the 878 study-participants from 42 practices.6 Results from the randomised controlled trial, which achieved 85% follow-up at 12 months, showed a mean total energy expenditure increase of 9.4 kcal/kg/week (p=0.001) and leisure exercise increase of 2.7 kcal/kg/week (p=0.02), or 34 minutes/week more in the intervention group than in the control group (p=0.04).6
SF-36 scores of self rated ‘general health’, ‘role physical’, ‘vitality’, and ‘bodily pain’ improved significantly more in the intervention group (5.95, 10.53, 5.36, and 6.51, respectively) compared with the control group (1.60, 4.16, 3.06, and 2.50, respectively) (p<0.05).6
Table 1. Baseline characteristics of less-active 40–79 year-old patients in general practice, by intervention and control group6
Table 2. Offset costs per patient for the intervention group compared with the control group (intention-to-treat analysis)
Ninety-five percent of intervention patients and 2.5% of control patients attending follow-up recalled receiving a Green Prescription in the previous 12 months, indicating a low level of ‘contamination’ of intervention.
The total discounted and annuitised national set-up and coordinating cost for the Green Prescription programme from mid 1996 to mid 2002 was NZ$2,861,016 (see Appendix 1). Approximately 34,708 patients received Green Prescriptions during that period. The programme set-up and coordinating cost per patient (excluding exercise specialist referral costs) was NZ$82.43 per Green Prescription recipient. The general practice-based delivery cost of the intervention and follow-up over the following 12 months was NZ$19.20 per patient (see Appendix 2). Of the 451 in the study, 410 (91%) were referred to the Sports Foundation exercise specialists. The total exercise specialist direct and overhead costs attributable to study patients was NZ$31,032.65 (see Appendix 3) or NZ$68.81 per intervention patient.
Table 2 shows the decreased healthcare costs per individual in the intervention compared with the control group, particularly in hospital costs, but with wide confidence intervals due to large individual variations in actual costs of hospitalisation. There was no significant difference in change in number or cost of days off work due to illness or accident between the groups for the year before and the year after the intervention. (Changes in rates of health care utilisation and days off work are presented in Appendices 4-6.) Personal exercise-related costs were NZ$26.96 per patient per year more in the intervention group (see Appendix 7).
Table 3 shows the cost from the programme-funders’ perspective was NZ$170.43/patient/year. Table 4 shows the cost effectiveness ratios for the Green Prescription with sensitivity analyses compared with those of the ‘Lifestyle’ and ‘Structured’ Project Active exercise programmes.12
The proportion of participants in the intervention who achieved 2.5 hours of at least moderate activity per week increased by 14.6% (66/451) compared with 4.9% (21/427) in the control group (p=0.003).6 Therefore, the incremental cost of converting one additional adult in the Green Prescription programme from sedentary to active over 12 months, compared with the control group, was NZ$1,756 in programme costs.
Table 3. Incremental cost per patient of the Green Prescription programme, including programme and offset costs and savings (intention-to-treat analysis)
* It was inappropriate to calculate total cost difference estimates taking offset costs into account because of the large confidence intervals and imprecision around the offset costs.
Table 4. Cost-effectiveness ratios for the green prescription compared with project active ‘lifestyle’ and ‘structured’ physical activity promotion programmes
#Offset costs are excluded from this analysis due to the large confidence intervals around the offset costs estimations. 1Using upper 95% confidence interval estimate of physical activity gain.6 2Using lower 95% confidence interval estimate of physical activity gain’; *Comparisons with the Project Active 6-month results were not used, as these values were even less cost-effective than at 24 months 12; 95% confidence intervals were not available for Project Active estimates. All costs were converted to New Zealand dollars using the December 2001 exchange rate, $NZ1=$US0.4157 or $US1=$NZ2.4056.
This study represents one of the most comprehensive cost-effectiveness analyses of a physical activity programme in primary healthcare to date. The Green Prescription programme cost per patient was NZ$170.45 from a programme funders’ perspective. Cost-effectiveness ratios were favourable compared with other physical activity interventions reported in the literature. Cost-effectiveness could not be calculated from a societal perspective because of large confidence intervals around offset costs.
Thirteen percent of patients attending their general practitioner during the recruitment phase were too ill to be screened, missed or refused screening for eligibility. In addition, one-third of those eligible declined to participate. There are few details available about those that chose not to participate, which may limit generalisability of results.
‘Usual care’ may have included some verbal advice about physical activity, 2.5% of control patients received a Green Prescription during the study year, and the control group also increased physical activity participation possibly due to participation in a trial about exercise. This may have diluted the effect of the intervention.
Private hospital cost data was not available. However, of the 337 participants that reported inpatient or outpatient attendance, only 41 used private hospitals (21 intervention and 20 control). When average daily public hospital costs were applied to self-reported days in private hospital for the year following the intervention, the total private hospital costs in the control group were substantially more than those in the intervention group (Appendix 5 footnote). Therefore hospital-related savings in the intervention group may have been greater than reported in this paper.
There are large 95% confidence intervals and imprecision around changes in major offset costs, particularly healthcare utilisation costs to the patient (NZ$18.62 [95% CI: -55.63–92.88]) and to the health funder (-$178.94 [95% CI: -728.58–370.70]), as well as productivity costs ($1.21 [95%CI: -522.06–524.49]). As a result, overall cost-effectiveness from a societal perspective could not be calculated.
Given this degree of variability in actual healthcare utilisation costs, it would take a very large study to have sufficient power to achieve confidence intervals that did not cross zero. Nevertheless, there was no evidence of increased costs in health care utilisation or loss of productivity as a result of the intervention.
This cost-effectiveness study was conducted prospectively, costing data collected was comprehensive, follow-up rates were high, and in almost all cases, actual costs, rather than estimated costs, were used. Accordingly, few assumptions were made. This is in contrast to many of the previous cost-effectiveness studies conducted of lifestyle interventions, which estimated costs retrospectively.12,16
The Green Prescription appears to be cost-effective when compared with other physical activity interventions reported in the literature, such as Project Active in the United States.12 Furthermore, the incremental cost of converting one additional person to an active state was NZ$1,756 using the Green Prescription. Using the United Kingdom the ‘Prescription for Exercise’ programme in primary care the incremental cost of converting one additional person to an active state was $NZ8,663 (UK£2,500).7
Although the costing structures and components may be quite different in these countries, the cost-effectiveness ratios of the Green Prescription appear favourable, as presented in Table 4. However, to allow comparisons with other types of interventions, a cost utility analysis is needed.
Ten percent more intervention patients than control patients went from ‘sedentary’ to ‘active’ and maintained this at 12 months. This has potential economic implications. For example, an estimated NZ$55 million could be saved in direct and indirect costs associated with ischaemic heart disease and hypertension if 10% of the population in New Zealand changed from ‘sedentary’ to ‘active’.17,5 The most recent New Zealand physical activity survey estimates that 878,000 adults over 18 years of age in New Zealand are not achieving 2½ hours of leisure-time activity per week.18
If all less-active adults were to receive a Green Prescription, the total programme cost (without offset costs), would be NZ$150 million to save at least NZ$55 million per year in costs associated with cardiovascular disease, alone. If changes detected after 1 year were permanent, then the programme may be cost-saving in approximately 5 years, assuming a 2-year delay19 before cardiovascular benefits were evident.
The potential savings would be even greater if quality of life benefits (demonstrated in SF-36 score changes), and other potential health benefits associated with increased physical activity, were considered. In addition, interventions become more cost-effective over time as the proportion of set-up costs declines.12
This study represents a cost-effectiveness analysis, using cost per physical activity unit gained as its primary outcome to allow comparison with previous community-based physical activity interventions. Modelling of the potential savings from health outcomes related to the increased proportion of active adults, and a cost-utility analysis are the next step and are underway.
The research will allow future comparison of cost-effectiveness of physical activity counselling in primary care with other lifestyle and pharmacological interventions.20
Author information: C Raina Elley, Senior Lecturer, Department of General Practice, Wellington School of Medicine, University of Otago, Wellington; Ngaire Kerse, Associate Professor, School of Population Health, University of Auckland, Auckland; Bruce Arroll, Associate Professor, School of Population Health, University of Auckland, Auckland; Boyd Swinburn, Professor, Physical Activity and Nutrition Research Unit, Deakin University, Melbourne, Australia; Toni Ashton, Associate Professor, School of Population Health, University of Auckland, Auckland; Elizabeth Robinson, Statistician, School of Population Health, University of Auckland, Auckland
Acknowledgements: The National Heart Foundation of New Zealand, Hillary Commission, Waikato Medical Research Foundation, and Royal New Zealand College of General Practitioners funded this study.
We also acknowledge and thank Sport Waikato and Pinnacle Independent Practitioners’ Association (for their contribution and support); the general practitioners, staff, and patients in the Waikato region of New Zealand (who participated freely in the study); Richard Milne (for advice about initial study design); and Jan Gaskin, Moira Johnson, Sharon Matangi-Nixon, Hayley Gaddes, Helen Dunn, Chris Drent, and Ruth Boyce (for data collection and entry).
Correspondence: Dr C Raina Elley, Department of General Practice, Wellington School of Medicine, PO Box 7343, Wellington. Fax: (04) 3855539; email: firstname.lastname@example.org
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