C O S T O F H E A L T H C A R E

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1 C O S T O F H E A L T H C A R E The additional cost of obesity to the health service and the potential for resource savings from effective interventions ADRIAN BAGUST, B. LYNNE ROBERTS, ALAN R. HAYCOX, STEVE BARROW * Background: Obesity affects 15% of men and 16.5% of women in the UK (1995). UK prevalence of obesity has doubled in 10 years and continues to rise: it is projected to reach 18 and 24% respectively by Obesity is a complex condition influenced by both genetic and environmental factors and is associated with reduced longevity and increased risk of serious co-morbidities including diabetes, coronary heart disease, stroke and hypertension. Methods: Data from a large population survey in north-west England allowed estimation of the additional direct costs to the NHS of major co-morbidities associated with obesity. The change in costs expected from a lower prevalence of obesity were projected. Results: Initial estimates suggest annual reductions in health care spending in England of up to 131 million per annum (1996 prices) may be possible with effective interventions for being overweight and obesity. This is equivalent to 11% (males) or 13% (s) of spending on the main co-morbidities and approximately 1% of overall expenditure. Conclusions: The number of grossly obese patients in the UK remains very small and the burden they place on the health service is not very serious. Most of the additional cost is for those moderately overweight (WHO grade 1) and research should concentrate on evaluating interventions that reduce the numbers in this group. Obesity often develops at an early age, but the more expensive co-morbidities appear years later. Thus, interventions targeted at younger age groups are more likely to provide significant cost savings, but must be evaluated over a lifetime to include the full impact of chronic co-morbidities. obesity results from an excess of adipose tissue (body fat), which constitutes 15-20% of total body weight in adult men and 25-30% in women. Obesity is thought to be a manifestation of a primitive survival mechanism which allowed humans to store excess energy as fat in times of plenty enhancing the chances of survival in periods of famine. In a modern industrialized society with ready access to high-energy foods combined with a sedentary life style, in many people the same process tends to lead to excess weight gain.' Rates of obesity are higher in developed countries than in underdeveloped or developing countries, though there are some notable exceptions; obesity is generally uncommon in Japan, 2^ whereas it is high in parts of India, most particularly amongst male medical doctors in Bombay. 4 Early studies of mortality led to the development of a single index of obesity, which is widely employed in the literature 5 - the body mass index (BMI). The WHO Expert Committee on Overweight 6 has classified the * A. Bagust', B.L Roberts 1, A.R Haycox 1, S. Barrow 2 1 Prescribing Research Group, Department of Pharmacology a Therapeutics, University of Liverpool, UK 7 North West Health Research Unit, Manchester, UK Correspondence: Dr Alan Haycox, Prescribing Research Group, Department of Pharmacology 8 Therapeutics, The Infirmary, 70 Pembroke Place, Liverpool L69 3GF, UK. tel , fax Keywords: cost, drugs, life style, obesity same five BMI ranges for men and women: < 18.5 is referred to as underweight, is normal, is termed grade 1 overweight, is grade 2 overweight and 540 is grade 3 overweight. In common parlance, a BMI of 30 or more is described as obese and BMI of 540 is considered morbidly obese. The 'Health Survey for England 1995' 7 estimated that 15% of men and 16.5% of women were obese, confirming an earlier finding 8 that adult obesity had doubled from 6 to 13% in men and from 8 to 17% in women between 1980 and At this rate of increase, obesity among men and women could reach 18 and 24% respectively by the turn of the century. Studies of life style over the last decade have emphasized that levels of physical activity are very low in many individuals. The 'Allied Dunbar National Fitness Survey" 9 and the 'Health Survey for England 1996' 10 found that 30-35% of men and women undertake less than four 20 minute periods of exercise per week. They found that only 20-30% of respondents participated in any vigorous activity. The increasing prevalence of obesity in children and adolescents is particularly worrying and this trend seems likely to lead to increases in a wide range of health problems in the future. With very few exceptions, obesity itself does not constitute a significant medical problem. Where medical problems do arise, these normally occur as a consequence of

2 Additional cost of obesity psychosocial rather than physical manifestations of obesity. However, a wide range of epidemiological studies have implicated obesity as a significant predisposing risk factor in a variety of disabling and life-threatening medical conditions. A number of studies 11 have also attempted to estimate the direct cost of obesity and associated morbidity yielding totals ranging from 1.5% (The Netherlands) to 7 8% (Sweden) as a proportion of overall health care costs. 12 One UK study estimated the annual cost of obesity at less than 30 million, but the cost of co-morbidities related to obesity at over 160 million. 1 -* All such studies emphasize the significant upward trend in health care costs that can be anticipated from an increased prevalence of obesity. However, quantifying such a trend is difficult as the nature and mechanism of the association between obesity and its co-morbidities are poorly understood. While a large volume of epidemiological evidence associates obesity with increased risk of death or chronic diseases, it is important to recognize that causal mechanisms have not generally been established. Interventions for the management of obesity (dietary modification and pharmacological or, in extreme cases, surgical interventions) are difficult to evaluate and require a long-term perspective to reflect the dominant role of chronic comorbid conditions on both survival and recurrent illness. Extrapolating apparent short-term clinical response to a particular treatment for obesity to anticipated cost savings may lead to significant overestimation. An alternative approach is to estimate and cost the proportion of health care costs which is attributable to the prevalence of being overweight within the population, as a means of scoping the maximum size of achievable benefits from any existing or future therapy. METHODS Study objectives The primary objective of this study is to estimate the major incremental costs incurred by the NHS which are associated widi obesity. A secondary objective is to estimate the magnitude of reductions in health care spending which could be expected from a population shift to a healthier distribution of body weight These estimates provide an upper limit on the financial benefits achievable from implementation of current or future antiobesity interventions, since it is not possible to determine the extent to which obesity may be confounded with other risk factors. Data sources Ideally we should look for a single data source which can directly link the consumption of health service resources with personal details for the same individuals to establish the presence and degree of obesity and its co-morbidities. To our knowledge no such database exists in the UK, so it is necessary to obtain prevalence and resource data from separate sources. Prevalence data were obtained from the North West Health Survey, which was conducted in 1992 using a self-reported questionnaire administered by post to a random sample of residents aged 18 years and over. The characteristics of respondents closely matched those of the underlying population for all important social and demographic variables. A total of 38,000 responses were obtained providing information on a range of demographic, health and life style issues, allowing examination of the relationships between height, weight, gender and recent experience of health problems. Pregnant s were excluded leaving a total of 35,000 individual records for analysis. Sixteen survey questions related to specific common health problems for which respondents had consulted a doctor in the previous 12 months, two questions concerned previous acute events which are indicative of chronic disease (stroke and heart attack) and one related to hypertension. The principal source of resource use data was the Hospital Episode Statistics (HES) data set for the north-western region of the NHS. Historical analyses of out-patient and in-patient activity were used to estimate out-patient resources and national Healthcare Resources Group (HRG) cost figures to quantify resource costs. A further question in the health survey allowed the frequency of consultations to be estimated. Analysis BM1 was calculated for each survey respondent An initial analysis of the survey data revealed that almost all morbidity/sex combinations showed some evidence of significant non-linear relationships with increasing BMI. The prevalence of obesity at different BMI thresholds for 10 year age bands was also examined and the strong influence of age upon obesity prevalence led to a thorough analysis of morbidities for each age group separately to obtain trend lines of prevalence against BMI. Six chronic conditions most frequently cited as obesity related were then examined in detail (coronary heart disease, stroke, diabetes, hypertension, varicose veins and haemorrhoids). The morbidity prevalence for each condition was multiplied by the proportion of the population with a BMI greater than or equal to a particular value to estimate the proportion of total morbidity in the population attributable to persons with BMI above any particular threshold. Analysis of HES data for the north-western region of England provided summaries of the total inpatient activity (admissions and bed days) linked to each morbidity. The relevant prevalence obtained from the health survey was then applied to estimate the proportion of in-patient resource usage which may be attributed to patients above a given BMI threshold. The 'excess' resource use is then the volume of resource above the level normally expected for persons at or below the selected BMI threshold. Out-patient attendances were estimated pro rata to inpatient admissions weighted for historic ratios of in-patientrout-patient usage by specialty. Details in the questionnaire of the number of consultations made by the respondent in the previous year were analysed in a similar

3 EUREAN JOURNAL OF PUBLIC HEALTH VOL NO W W+ Figure 1 Prevalence of obesity by age and sex fashion to estimate the excess volume of contacts associated with obesity. RESULTS Prevalence of obesity and related conditions The prevalence of obesity in the general population of north-west England varies by age and sex (figure I). The proportion of overweight individuals rises steadily with age, but peaks at age years, before declining quite sharply: it is not clear whether this downturn results from differential mortality (fewer obese people surviving to i>70 years), reflects a consequence of the ageing process on body weight or is in part a cohort effect. The proportionate rate of growth in prevalence with age (and subsequent decline) is similar for all grades of obesity, suggesting that there is no evidence that the degree of obesity tends to worsen over time in adults. Figure 2 illustrates the age-related prevalence for four diseases most commonly cited as associated with obesity. In each case, patients report very low levels of disease among young adults but steep trends are apparent from mid-40 years onward. Generally, men show higher prevalence rates than women. Coronary heart disease, stroke and diabetes follow broadly similar pathways over time, continuing to increase into extreme old age. However, hypertension appears to develop considerably earlier (15 20 years) and then to peak around age 60 years before beginning to decline, following a similar trajectory to that found for obesity (figure I). This could be indicative of a more immediate and direct link between obesity and hypertension than applies to the other three conditions. The timing of the appearance of obesity relative to other diseases is important when considering the existence and nature of causal associations. If it were shown that the prevalence of a disease precedes the development of obesity, then obesity could not be a direct cause of the disease. However, the survey data shows that, for each of these four major health problems, obesity cannot be excluded 9 as a potential causal factor, nor can possiblereductionsin 1S » Figure 2 Prevalence of major obesity-related conditions the prevalence of these common diseases be precluded should population rates of obesity be reduced. In order to capture the influence of age on the prevalence of both obesity and the associated morbidities it was necessary to determine prevalence/bmi trends for each morbidity for each age group and gender separately: this involved six conditions (the aforementioned four plus varicose veins and haemorrhoids) and 16 age/sex groups - a total of 96 prevalence versus BMI potential trends. The results are summarized in table 1 - a positive gradient reflects a significant (p<5) linear or polynomial trend with positive gradient fitted by ordinary least squares (OLS) regression. Overall it is clear that obesity is most strongly related to disease in the middle age bands (35-74 years), with very little evidence of any effect among the young or the elderly. A similar absence of a strong gradient among the elderly has been reported previously for mortality. Delineating the relationship between BMI and use of health care resources involves combining the prevalence of disease and the distribution of BMI in the population by age and sex. In all conditions, although the prevalence rises steadily with BMI, this is more than counterbalanced by the fall off in the obesity prevalence rate (illustrated for coronary heart disease in males infigure3). For the purposes of evaluating anti-obesity therapies, the prime focus is on the degree of obesity above which intervention would be appropriate or, conversely, the effective maximum BMI as a therapeutic target. To determine the potential for offsetting health service savings it is necessary to estimate the excess morbidity associated with

4 Additional cost of obesity residents above any BMI threshold, compared to the morbidity expected if all such individuals experienced no greater ill-health than those at or below the threshold. Excess morbidity as a proportion of total morbidity at a range of BMI thresholds is also shown in figure 3. In general, when the obesity threshold is set above approximately 30, the proportion of prevalent disease which might be avoidable by anti-obesity interventions becomes very small (from maxima of 3.7% for diabetes in s and 23% for hypertension in males to only 0.3% for haemorrhoids). *«> Excess hospital costs by major morbidity The analysis of regional HES data provided a direct attribution of in-patient and day case resources used in by the six major morbidities by age and sex. Corresponding out-patient costs were estimated by assuming that the same proportion of out-patients as in-patients is obese and using historic estimates of relative activity rates at specialty level. It is also assumed that explicit interventions for obesity are reserved for the most seriously obese and therefore 100% of the identified costs are considered 'excess' regardless of BMI threshold. visit costs could not be related to specific disease areas on the basis of currently available data and are therefore omitted from the morbidity-based analysis. It is recognized that analysis by disease relates only to the identifiable immediate cause of admission or treatment and may not capture information about underlying causes of the presenting problem. For example, poorly controlled diabetes leads to a wide spectrum of micro- and macrovascular complications. Some of these (such as diabetic leg ulcers) will be included in the diabetic category, but some strokes and many acute admissions for heart disease Table 1 Morbidity trend analysis by BMI Age group (years) Males s » S2 S Figure 3 Prevalence of coronary heart disease among males and excess prevalence at a range of BMI thresholds among diabetics will not be attributable to diabetes. Indeed, all these diseases and their complications are part of a multifactorial complex and it was not possible to distinguish the degree of overlapping morbidity in the present investigation. Coronary heart disease Stroke Diabetes Hypertension Varicose veins Haemorrhoids Increase for BMI 30 Increase for BMI 30 Increase for BMI Non-linear - max. at BMI

5 EUREAN JOURNAL OF PUBLIC HEALTH VOL NO. 4 Table 2 shows the results of these calculations expressed in terms of the excess hospital cost per 1,000 population for BMI thresholds of 25, 30 and 35. Coronary heart disease is by far the largest component of obesity-related excess cost, with in-patient costs more than eight times greater than out-patient costs. Diabetes is the next largest source of extra cost, though only approximately 30% the size of the heart disease effect. It is noticeable that, for diabetes, the in-patient and out-patient components are of comparable size. The other four co-morbidities as well as obesity itself, are all relatively insignificant, contributing only 10-20% of the total except for those with the most extreme obesity. Men have consistently higher overall excess costs than women, though this is wholly attributable to the much higher hospitalisation rates among men for heart disease. Overall excess costs by age group It is possible to include the estimated costs of consultations and prescribing as in table 3, though these do not significantly alter the overall position. The population ratios are calculated per 1,000 people in the specific age group and, therefore, provide a clear indication of the variation in treatment intensity by age. Here the dominant effect of obesity is apparent in the years age range. Comparison of the figures for different BMI thresholds reveals how rapidly the population burden of excess health care cost declines as the BMI threshold is raised. In the peak age range, the proportion of the major excess co-morbid costs attributable to overweight and obese patients for in-patient care (i.e. the majority element) comprises approximately 17% of die total for men and 23% for women using a BMI threshold of 25. These fall Table 2 Obesity-related excess hospital costs ( s) per 1,000 population by disease and BMI rjireshold BMI thresho Id Sex Male Male Male Patient type & &. & Obesity Hypertension J Diabetes to approximately 4-0 and 3.8% respectively with a BMI threshold of 30. Over all age groups and types of cost, the corresponding figures are 10.7 and 12.6% for a BMI threshold of 25 and 1.2 and 1.6% at a BMI of 30. In cash terms, applying the relationships derived from the north-west morbidity data to the population of England, this excess resource use amounts to approximately 131 million (1996 prices) with a BMI threshold of 25 or 15 million with a threshold of 30. This is equivalent to 1% or % of total health care spending respectively. DISCUSSION There have been relatively few economic studies undertaken in the area of obesity. Most of these have been formulated as burden of disease studies rather than addressing the more important issue of how best to intervene to reduce the level of such a burden. One of the major reasons for this is the often conflicting clinical evidence concerning the efficacy of treatment interventions. There is a great need for high-quality and large-scale studies evaluating die comparative long-term cost-effectiveness of the range of interventions available in obesity management. There are positive conclusions from this study which may inform a strategic approach to the range of health problems associated with obesity. Firstly, the absolute number of the grossly obese is still very small and, although their relative risks of consequent (or co-morbid) diseases are high, the proportionate burden on the health service budget overall may not be as serious as is often supposed. Nonetheless, the likelihood of a steady growth in the numbers of overweight people remains an important public health issue. Disease area Coronary HD Stroke Varicose veins J Haemorrhoids Total hospital costs : in-patient; : out-patient Coronary HD: coronary heart dueaie

6 Additional cost of obesity The preponderance of overweight people is among those classified as gtade 1 overweight, implying that future investment targeted at achieving sustained response among these groups may yield greater societal benefits in terms of reduced treatment costs in the long-term. Finally, it is clear that obesity can develop at a relatively early age and, if unresolved, is probably implicated as a significant factor in promoting additional mortality and morbidity from middle age onward. Thus, interventions may be better directed at identifying and ameliorating obesity developing among the younger age groups, radier than focused on the small number of older grossly obese individuals in whom chronic vascular diseases are likely to be already well advanced. The value of interventions to reduce obesity will be limited in the elderly who are already suffering the effects of a lifetime of cumulative exposure to obesity and its complications. At some point in middle age the balance of intention should switch from 'prevention' to 'relief and rescue'. Hill and Roberts 15 recently reported significant bias in self-reported height and weight measurement in Somerset, leading to underestimation of BMI for the majority of respondents. If the Somerset findings are applied to the north-west survey data, the number of people classed as being overweight would be increased on average by 5.6% (BMI 25) or 7.4% (BMI 30). This does not affect the relationships within the analysis, but does alter the magnitude of excess costs related to being overweight and obesity, which on this basis become 138 million at a BMI Table 3 Obesity-related excess hospital and costs ( s) per 1,000 population by age and BMI threshold BMI threshold Sex 25 Male 30 Male 35 Male Service type,, I/P O/P I/P O/P,,,, of 25 and 16 million at a BMI of 30. Future self-reporting surveys should consider following the Somerset model by using a measured subsample to validate/adjust for reporting bias. The methodology described involves a number of assumptions which are open to question, most notably that resource use intensity among obese patients is similar to that of others with the same diseases. However, since it is likely that any deviation from this assumption would involve obese patients needing more care rather than less, the additional cost estimates related to obesity in this analysis can be considered conservative. Other assumptions concern the validity of self-reported morbidity, the integrity of HES coding, the relationship between inpatient and out-patient activity and, indeed, the appropriateness of BMI in relation to morbidity rather than mortality (for which it was originally designed). Many of these issues will not be resolved definitively until large comprehensive studies are conducted embracing body measurement, morbidity assessment and resource use from the same population samples. These results emphasize the considerable cost to health services arising from the diseases associated with obesity and offer an economic baseline for examining the cost of interventions in obesity management. Whilst die direct cost to the NHS is substantial, the indirect cost must not be minimized and quality of life considerations should integrated into health care decision making in this important therapeutic area. Age group (years) U Total costs : in-patient; : out-patient

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