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.

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

(Click here to view Table 1 and Table 2)

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.

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

(Click here to view the Appendices)

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: c.elley@wnmeds.ac.nz

(Click here to view the references)